Gary Fleming, Virginia Department of Conservation and Recreation
Plants Database provides a distributional map of
HABITAT TYPES AND PLANT COMMUNITIES:
Great laurel is an important species in several eastern plant communities, most notably southern Appalachian forest communities where it occurs as an understory dominant on millions of acres . It often occurs as a dominant shrub in Table Mountain pine (Pinus pungens) and pitch pine (P. rigida) forests [29,77], xeric coniferous heathlands , mixed heath balds [77,122,127], chestnut oak (Quercus prinus) forests and heaths [77,122], lower elevations of the southern Appalachian spruce zone (red spruce (Picea rubens)) [1,62], and scarlet oak-red maple forests (Q. coccinea-Acer rubrum) . It is also a dominant shrub in mixed mesophytic forests , particularly eastern hemlock (Tsuga canadensis) [57,77,88] and oak-hickory (Quercus spp.-Carya spp.) forests (formerly oak-American chestnut (Castanea dentata)) [15,77,83,127]. Great laurel is common in northern red oak-white oak forests (Q. rubra-Q. alba)  and northern red oak-yellow-poplar (Liriodendron tulipifera)-chestnut oak forests . Great laurel is commonly associated with mountain-laurel (Kalmia latifolia) [26,127]; together these are the 2 most typical and frequent shrubs of the southern Appalachian forest .
Though great laurel often occurs as a component in various mixed shrub associations and in the understory of Appalachian forest types, the predominant growth form is that of a dense thicket in which crown closure has occurred and nearly all other herbs, shrubs, and trees have been excluded [26,57,62,63,77,90]. Here great laurel can achieve greater than 80% coverage . For more information on great laurel thickets see Stand Structure.
Plant communities where great laurel is a dominant species are described by state as follows:
GENERAL BOTANICAL CHARACTERISTICS:
This description provides characteristics that may be relevant to fire ecology, and is not meant for identification. Keys for identification are available (e.g., [44,92,108]).
Great laurel is an evergreen shrub or small tree [24,92,105,109,121] that grows up to 40 feet (12 m) tall [15,18,44,63,72,84,90,99,105,108,109,121,127] and 25 feet (7.5 m) wide . Mature height depends on climate and varies from 3 feet (1 m) in the colder northeast to 40 feet in the southeast [66,106]. Growth form often exhibits a crooked trunk  reaching 1 foot (0.3 m) in diameter [18,90,99,108,121] and heavy, contorted branches . Multiple stems grow from a large root crown, and individual stems may reach 100 years old .
Great laurel's thick, leathery leaves are oblanceolate to narrowly elliptic, 3 to 14 inches (8-35 cm) long and 0.8 to 3 inches (2-8 cm) wide [15,18,44,72,86,92,108,109]. In cold temperatures or during droughts, great laurel leaves roll up around the axis of the leaf [15,109]. Leaves are retained for up to 8 years, and once shed, are slow to decompose . Great laurel leaf area has been positively correlated to the likelihood of flowering, with the probability of flowering greatest for younger shoots (≤ 2 years) . The rose to white colored flowers of great laurel are numerous, 1.5 inches (3.5 cm) wide, and borne in an umbel-like inflorescence [15,44,66]. Great laurel fruits are oblong capsules that split along the sides soon after ripening to release large numbers of seed (approximately 400 seeds per capsule) [18,97]. Seeds are 1.5 to 2 mm long .
Stand Structure: The predominant growth form of great laurel is a dense thicket that excludes nearly all other plants under its closed crown [26,57,62,63,77,90]. Here great laurel can achieve greater than 80% coverage . These thickets grow 10 to 23 feet (3-7 m) tall [10,84,108], and may form an almost unbroken shrub stratum. In one study, great laurel attained an average height of 8 to 10 feet (2.5-3 m) with nearly impenetrable, low-branching woody growth .
RAUNKIAER  LIFE FORM:
Great laurel reproduces primarily through layering, root sprouting, or stump sprouting, and occasionally by seed when conditions are conducive [96,109]. Despite its shade tolerance, any great laurel regeneration, whether by seed or vegetative growth, requires openings in the canopy before thickets can form or increase in size . Site requirements under which great laurel can reproduce are often quite restrictive; reproduction and colonization by seed often occurs in very scattered patches . An abundance of seedlings has been linked to drier great laurel thickets with more open canopies, while thickets with wetter conditions and denser canopies produce very few seedlings but exhibit profuse layering [44,91,103].
Pollination: Great laurel is insect-pollinated .
Breeding system: Romancier  reports some evidence of self-pollination in great laurel, implying it is at least sometimes monoecious.
Seed production: Great laurel seeds are produced in capsules, each containing 300 to 400 seeds 1/32 inch long . One study found that a great laurel thicket produced an average of 300 seeds per square foot .
Some authors [76,78,123] have observed that only twigs receiving full sunlight flower.
Seed dispersal: Great laurel seeds are dispersed passively or by wind [55,97,109].
Seed banking: Reports of great laurel seed banks are inconclusive. Romancier  states that great laurel "seed viability may persist for several years under normal forest conditions". A study of low- to mid-elevation slopes at Coweeta Hydrologic Laboratory in North Carolina found some evidence of great laurel seed banking, though a persistent seed bank could not be unequivocally determined . A study of riparian forest (dominated by black cherry (Prunus serotina), red maple, sugar maple (A. sacharum), and American beech) seed banking on the Allegheny Plateau, Pennsylvania found no evidence of great laurel seed banks .
Germination: Great laurel requires moist, partially shaded areas for germination and growth [97,109]. However, because some light is required for germination, the dense shade and thick litter layer that typically develops beneath mature great laurel is an effective physical barrier to seedling establishment [90,99]. No stratification is required for great laurel germination; seeds can germinate as soon as they are released from the capsule . Germination rates range from 75% to 90% .
Seedling establishment/growth: Great laurel seedlings may be highly specific in their establishment and growth requirements, including relatively high humidity, moderate light exposure (e.g., lightly wooded forest), and soil pH 3.5 to 5.0 [18,96,105]. Seedlings grow best in partial shade and can survive in deep shade, but do poorly in fully exposed sites . In extremely dense shade, great laurel growth is straggly and crooked, with leaves confined almost entirely to new growth at stem tips. Branches grow only 1 to 2 inches (2.5-5 cm) per growing season, and the number of blooms produced per season is relatively small . In less dense shade, plants are more upright with thick compact stems, leaves more or less all along the stems, branches exhibiting 6 to 8 inches (15-20 cm) terminal growth per season, and many blooms . Plocher , in his study of great laurel population dynamics in West Virginia, found no seedlings within a live great laurel thicket. The seedlings that did establish were always in light to medium shade adjacent to thickets (up to 100 feet distant). In general, great laurel exposed to high sunlight (such as with overstory removal) display reduced vigor .
Great laurel seedlings grow well on bare mineral soil but may be susceptible to frost heaving . Once established, great laurel has a "tremendous" capacity for avoiding cavitation during freeze-thaw cycles .
Vegetative regeneration: Great laurel reproduces clonally . It benefits from overstory disturbance, forming even-aged thickets via rapid vegetative spread . Once a thicket is formed, little outward spread occurs unless the thicket is disturbed . Great laurel sprouts vigorously following disturbance [86,90] and stems layer readily to fill openings in thickets . Layering is one of the principal means of vegetative regeneration in natural stands [78,109]. Branches that bend to the ground, especially on the perimeter of the stand, form a root system where the branch contacts the ground. Shoots and sprouts develop from the root system to contribute to the spread of a stand, and suckers grow profusely when stems are cut [109,128]. A study of Appalachian oak forests found the density of great laurel was significantly greater (P<0.05) in gaps caused by ice storm damage than in understory plots .SITE CHARACTERISTICS:
Great laurel is shade tolerant, generally occurring on sites with medium to dense shade receiving little direct sunlight [90,105]. Optimum site condition is medium shade produced by a high canopy . Great laurel growth is inhibited both by high irradiance and by low water availability [69,70,105]. These factors limit growth of great laurel on southwestern slopes . Twig elongation in low, moist, sunny sites is 25% to 30% greater than on dry, exposed sites at higher elevations. The mesic sites produce 50% to 100% more leaves and the mean weights of these leaves are 25% to 100% greater than on xeric sites . In a southern Appalachian study at Coweeta Hydrological Laboratory, North Carolina, great laurel understory with >70% coverage was common in valley bottoms and north-facing slopes, while a mix of great laurel and mountain-laurel was common on south-facing slopes and along mid-elevation slopes. Mountain-laurel occurrred in greater numbers with increasing distance from streams .
Soils: Great laurel prefers deep, well-drained, acidic soils (pH 3.55 to 5.6) [18,26,30,72,77,90,97,105,105,123] high in organic matter, where the litter produces a thick, peat-like humus [18,99]. In xeric heathlands, it is also found on nutrient poor soils . Ectomycorrhizal associations improve great laurel fitness in nutrient-poor, acidic soils where availability of soluble inorganic nutrients is likely to be low. In particular, these associations improve phosphorus uptake . Great laurel is generally unable to colonize high pH soils; establishment of seedlings and layering of branches is potentially inhibited where pH is >6.0 .
Great laurel leaves and roots are rich in phenolics and other organic compounds. According to an eastern Kentucky study of single-tree influence on soil properties, the release of these compounds through decomposition "results in intensified leaching and acidification of soil, and may interfere with mineral soil retention of basic cations liberated from decomposing organic matter". By reducing pH on sites where they are established, great laurel thickets prevent herbaceous growth and establish stable boundaries over time .
Elevation and Aspect: Great laurel occurs from sea level to 6,000 feet (1,830 m) [4,40,66,72,92,99,120]. Slope aspect is generally more important in great laurel success than topography , with better development found on north-facing slopes [33,70,105]. Great laurel is also present, however, on east, west, and dry southern exposures .
Climate: Great laurel generally prefers cool, humid climates with annual
precipitation >79 inches (2,000 mm) . Great laurel thickets maintain a favorable
microclimate by reducing summer temperatures, excluding desiccating winter winds,
moderating cold temperatures, and increasing relative humidity . Arora and
others  report that great laurel is generally cold-hardy to -62 °F (-52 °C).
Sakai and others  offer the following limits for specific plant
tissues: flower buds are cold hardy to -16.6 °F (-27 °C); xylem to
-31 °F (-35 °C); and leaf, vegetative bud, and cortex to -76 °F (-60 °C).
Great laurel is often found in climax forest associations . It is suited for low light conditions and flourishes in shaded areas . Great laurel is also quick to occupy open sites (often forest gaps) [95,96], and may aggressively invade cleared or disturbed land in areas of high moisture and humidity . Great laurel may not be initially competitive at low density with vigorous overstory trees. However, once established, great laurel is capable of preventing other species from regenerating and competing under its dense canopy [4,53,54,89,95,112].
Where extensive mortality has eliminated most of the overstory, great laurel forms a thick and continuous subcanopy known locally as "laurel slicks" or "laurel hells" . In southern Appalachian forests, great laurel thicket development has been linked to limited livestock grazing , fire exclusion [20,43], and the widespread loss of American chestnut trees from chestnut blight [4,127]. The canopy openings resulting from disturbance [4,127], combined with the loss of great laurel inhibition by allelopathic properties of American chestnut litter , likely permit the establishment of great laurel thickets, which in turn reduce or even eliminate the recruitment of overstory trees [4,32,37]. The process of gap formation and recolonization plays an important role in the structure and composition of southern Appalachian forests [95,96]. Where great laurel is present, however, it plays a greater role in determining species richness and diversity than gaps or gap size, and alters forest structure. Great laurel dominates the midstory, adversely affecting mid- and understory development and diversity, and limiting advance regeneration of overstory tree species [95,96,112]. Where great laurel was present, Rivers and others  found significantly lower (P<0.05) species richness and density in both the herbaceous understory and midstory components of gap regeneration in a Blue Ridge Mountain study of riparian areas. Shade-intolerant midstory species were almost completely eliminated, and shade-tolerant species were severely reduced, preventing recruitment into the overstory . A study at Coweeta Hydrologic Laboratory also found that tree species establishment in canopy gaps of southern Appalachian forests was a function of gap area, age, topographic position, and cover of great laurel. Gaps containing over 50% great laurel cover had significantly lower (P=0.01) tree seedling density (primarily northern red oak) than all other gaps, including those with >50% mountain-laurel cover . Another study at Coweeta, simulating open to closed canopy conditions combined with the presence of great laurel, also suggested that in addition to light limitation associated with great laurel, low soil moisture and allelopathic compounds under great laurel thickets may inhibit red maple success . For more information and discussion regarding the effects of great laurel on forest structure and canopy tree species, see Other Management Considerations.
Heath balds, which are often dominated or codominated by great laurel, are
found in both disturbed and undisturbed areas. They have been considered both as
pioneer successional communities on rocky and shallow-soiled ridges and as
stable "end points" of succession. Some heath balds have developed from
forest-heath communities after canopy disturbance [77,119]. Following the loss of the
tree layer, deep leaf litter, acidic soils, and dense shade may prevent
reestablishment of tree species. Many heath balds, whether the result of
disturbance or not, become stable shrub communities , with
exposure producing microclimate and edaphic conditions to maintain
Great laurel produces 1 annual leaf cohort  in a growth period that begins in early May [76,76,78]. The flowering period of great laurel varies from late May in the southern parts of its range to August in the northern areas [18,44,66,72,86,92,97,103,106,108,123,126], beginning when approximately 60% of current twig growth is complete [76,78]. Twig growth continues until late summer, when the enlargement of flower buds in August terminates the growing season [76,78]. Fruit develops in September and October , with seed fall in November .
Leaf mortality occurs during late August and September . Abscission
begins in late August, but senescent leaves may remain on great laurel
through November [78,86]. In an Appalachian study of great laurel, leaf
mortality was primarily due to senescence (as opposed to herbivory or
pathogens) . Leaves can remain on great laurel for 7 or 8 years
[18,27,76,78,86] under a tree canopy; however, at Virginia
study sites where the overstory was absent, leaf survivorship decreased
to zero after 3 years. Leaf survivorship is greater in low light environments
[84,86] because great laurel chloroplasts are rapidly damaged in high
light environments [82,84,86]. Decreased irradiance also results
in decreased shoot growth, earlier initiation and cessation of annual
growth, and reduced woody biomass in relationship to leaf area .
Fire regimes: Woodland and forest communities in which great laurel occurs have a range of fire regimes including replacement, mixed-severity, and surface fires (see the fire regime table below). Most fires in these regimes are of low or mixed-severity, particularly in the Southern Appalachian and Southeastern regions. Fire intervals are wide-ranging, with low-severity fires averaging 4-year intervals in some communities to 100 or 1,000 years in other communities. Fires of mixed-severity and stand-replacing fires are much less frequent. Great laurel is well-adapted to these predominantly low-severity fire regimes, with its ability to survive fire through sprouting [56,75,98] and spread into canopy openings through stem layering and suppression of other species (for more discussion of these characteristics, see Successional Status and Other Management Considerations). In the southern Appalachians, where great laurel is likely to form dense, pure understories, fires are neither severe enough or frequent enough to eliminate great laurel. Fire exclusion in the southern Appalachians has contributed to the spread of great laurel . Though occasional fires serve to increase the vigor of great laurel populations, annual intense burning over extended periods, as was historically common in many Appalachian forests, resulted in the eventual elimination of great laurel from many areas . Baker and Van Lear  speculate that historic fires top-killed great laurel, allowing other species to grow ahead of its sprouting, and frequent fires during the growing season could have completely killed individual stems.
Great laurel is also well-adapted to fire regimes with a high proportion of stand-replacing fires. If present in a community, great laurel is effective at colonizing canopy gaps and maintaining an understory presence. Following large-scale stand-replacement events, great laurel often sprouts and forms dense thickets where reestablishment of overstory species is substantially reduced. Great laurel often dominates xeric coniferous heathlands in the southern Appalachians, a vegetation type that is maintained in part by fire . Heath balds likely represent secondary successional communities following disturbance, especially fire in extreme exposure sites . Once established, heath balds can also be considered topographic climaxes, with exposure producing microclimate and edaphic conditions to maintain them [77,120].
The following table provides fire regime information that may be relevant to great laurel. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find Fire Regimes".
|Fire regime information on vegetation communities in which great laurel may occur. For each community, fire regime characteristics are taken from the LANDFIRE Rapid Assessment Vegetation Models . These vegetation models were developed by local experts using available literature, local data, and/or expert opinion as documented in the PDF file linked from each Potential Natural Vegetation Group listed below. Cells are blank where information is not available in the Rapid Assessment Vegetation Model.|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Great Lakes Forested|
|Northern hardwood maple-beech-eastern hemlock||Replacement||60%||>1,000|
|Surface or low||76%||11||2||25|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Eastern woodland mosaic||Replacement||2%||200||100||300|
|Surface or low||89%||4||1||7|
|Rocky outcrop pine (Northeast)||Replacement||16%||128|
|Surface or low||52%||40|
|Surface or low||65%||12|
|Oak-pine (eastern dry-xeric)||Replacement||4%||185|
|Surface or low||90%||8|
|Northern hardwoods (Northeast)||Replacement||39%||>1,000|
|Eastern white pine-northern hardwoods||Replacement||72%||475|
|Surface or low||28%||>1,000|
|Northern hardwoods-eastern hemlock||Replacement||50%||>1,000|
|Surface or low||50%||>1,000|
|Appalachian oak forest (dry-mesic)||Replacement||2%||625||500||>1,000|
|Surface or low||92%||15||7||26|
|Northeast spruce-fir forest||Replacement||100%||265||150||300|
|Southeastern red spruce-Fraser fir||Replacement||100%||500||300||>1,000|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Southern Appalachians Woodland|
|Appalachian shortleaf pine||Replacement||4%||125|
|Surface or low||92%||6|
|Table Mountain-pitch pine||Replacement||5%||100|
|Surface or low||92%||5|
|Southern Appalachians Forested|
|Bottomland hardwood forest||Replacement||25%||435||200||>1,000|
|Surface or low||51%||210||50||250|
|Mixed mesophytic hardwood||Replacement||11%||665|
|Surface or low||79%||90|
|Surface or low||89%||6||3||10|
|Eastern hemlock-eastern white pine-hardwood||Replacement||17%||>1,000||500||>1,000|
|Surface or low||83%||210||100||>1,000|
|Oak (eastern dry-xeric)||Replacement||6%||128||50|
|Surface or low||78%||10||1||10|
|Appalachian Virginia pine||Replacement||20%||110||25||125|
|Surface or low||64%||35||10||40|
|Appalachian oak forest (dry-mesic)||Replacement||6%||220|
|Surface or low||79%||17|
|Southern Appalachian high-elevation forest||Replacement||59%||525|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Surface or low||97%||4||1||5|
|Longleaf pine (mesic uplands)||Replacement||3%||110||40||200|
|Surface or low||97%||3||1||5|
|Longleaf pine-Sandhills prairie||Replacement||3%||130||25||500|
|Surface or low||97%||4||1||10|
|Surface or low||10%||43||2||50|
|Atlantic wet pine savanna||Replacement||4%||100|
|Surface or low||94%||4|
|Coastal Plain pine-oak-hickory||Replacement||4%||200|
|Surface or low||89%||8|
|Atlantic white-cedar forest||Replacement||34%||200||25||350|
|Surface or low||59%||115||10||500|
|Loess bluff and plain forest||Replacement||7%||476|
|Surface or low||85%||39|
Replacement=Any fire that causes greater than 75% top removal of a vegetation-fuel type,
resulting in general replacement of existing vegetation; may or may not cause a lethal
effect on the plants.
Mixed=Any fire burning more than 5% of an area that does not qualify as a replacement, surface, or low-severity fire; includes mosaic and other fires that are intermediate in effects.
Surface or low=Any fire that causes less than 25% upper layer replacement and/or removal in a vegetation-fuel class but burns 5% or more of the area [50,64].
Stems less than 2 inches (5 cm) DBH are more susceptible to fire
than larger stems. A North Carolina prescribed burn resulted in 70% of
stems less than 1.0 inch top-killed, but only 5% of stems over 3.0
inches died .
PLANT RESPONSE TO FIRE:
Great laurel typically sprouts vigorously after the aboveground portions are killed by fire [56,75,98]. A fall prescribed burn in North Carolina top-killed 70% of great laurel less than 1inch (2.5 cm) DBH, but 17 months after the burn, nearly all the top-killed great laurel had sprouted .
DISCUSSION AND QUALIFICATION OF PLANT RESPONSE:
No additional information is available on this topic.
FIRE MANAGEMENT CONSIDERATIONS:
Great laurel has increased in the Appalachian Mountains due to fire exclusion [75,95]. Historically, great laurel occurred primarily in riparian zones, but fire exclusion and the cessation of fire use as a management tool in the 20th century, combined with other factors, allowed great laurel to expand into other areas under some conditions. For more information on the expansion of great laurel, see Other Management Considerations. Baker and Van Lear  speculate that, historically, fires in forests of the southern Appalachians may have top-killed great laurel and allowed other species to grow ahead of its sprouting, while frequent fire could have completely killed individual stems.
Great laurel has been described as a "serious woody weed" in the southeastern United States . Prescribed fire has been used to control great laurel with limited success . A fall prescribed burn to control great laurel on the Bent Creek Experimental Forest in North Carolina found that some shoots survived fire and vigorous sprouting occurred the following spring. The sprouts were "very susceptible" to herbicide applications in the second postfire growing season, with nearly 100% top-kill achieved .
A spring prescribed burn conducted in a dry, mixed-oak (Quercus spp.) community type at Wine Spring Creek Watershed, North Carolina reduced frequency of great laurel but had little effect on density (see table below) . More information on this prescribed fire and postfire response of plant community species can be found in the Research Project Summary Early postfire effects of a prescribed fire in the southern Appalachians of North Carolina.
Great laurel abundance before and after prescribed fire (April 1995) at Wine Spring Creek watershed, North Carolina 
|Pre-burn (July 1994)||Postfire year 1 (July 1995)|
|Average basal area (m²/ha)||7.231||7.789|
If fire is used to control great laurel, desired tree seedlings should be planted immediately in patches with complete top-kill to overcome vigorous great laurel sprouting .
Great laurel is poisonous to horses, causing labored breathing, nausea, constipation, diarrhea, and death .
Palatability/nutritional value: The following tables describe great laurel nutrient levels. The first is based on plant structure; the second table is based on leaf age.
Great laurel leaf nutrient levels (% dry weight), Coweeta Hydrologic Laboratory, North Carolina 
Cover value: Great laurel provides valuable winter and escape cover for white-tailed deer, eastern cottontail, black bear, snowshoe hare, ruffed grouse, wild turkey, and many songbirds [18,90,97]. Dense thickets of great laurel provide den sites, daybeds, and escape cover for black bears .VALUE FOR REHABILITATION OF DISTURBED SITES:
Seeding, layering, and cutting are the major means of propagating great laurel . Great laurel propagates well from stem cuttings [59,124,125]; however, based on a series of greenhouse experiments in Poland, increased age of stock plants may reduce rooting of stem cuttings . Hormone treatments are useful in stimulating root development of great laurel cuttings. For further details on hormone treatments and rooting success, see Williams and Bilderbeck [124,125]. Under cultivation, great laurel usually reaches 13 to 16 feet (4-5 m) tall .
Mature great laurel seeds germinate with no pretreatment  but require light immediately after imbibing for germination [6,11,46]. If imbibed seeds are not exposed to light or if exposure is delayed, secondary seed dormancy may be induced, preventing germination . Romancier  found germination rates in a field study ranged from 25% to 71%. A greenhouse study of great laurel seeds and watering regimes found average germination of 79%. The highest germination rate (88%) was reached with intermittent mist irrigation, compared to 77% with mat irrigation or 69% with hand-sprinkling irrigation . Gibberellic acid treatment for 36 hours at 0, 50, 200, and 1000 ppm did not affect germination . In a laboratory study, great laurel germination rates reached 92% to 97% after 21 days. Experimental conditions included photoperiods of >4 hours and alternating temperatures of 77/59 °F (25/15 °C) . Baskin and Baskin  report optimum germination of great laurel at 79/70 °F (26/21 °C). Great laurel seed may be kept at room temperature if it will be used within 2 months , but seed viability can be maintained for longer periods with cold storage. In a laboratory study, viability was relatively unchanged after 5 years storage at constant 0 °F (-18 °C) and at 39 °F (4 °C), with total germination of 88%. Storage at 73 °F (23 °C) for 4 years, however, essentially reduced viability to zero .
Great laurel seedling growth was evaluated under laboratory conditions that
included 9 hour days at 64, 72, 79, or 86 °F (18, 22, 26, 30 °C) combined with
15 hour nights at 57 (14 °C), 64, 72, or 79 °F. Total dry matter produced was
greatest with 79 °F days and lowest with 64 °F days. The optimum day/night cycle
for dry matter production was 79/72 °F. Leaf area was optimized with 64 °F nights,
while 72 °F nights maximized total plant, leaf, and stem dry weights .
No information is available on this topic.
Great laurel's inhibition of canopy tree regeneration may cause incomplete or slowed succession . Possible sources of inhibition include allelopathy, competition for resources including light, physical and chemical attributes of the forest floor and soil, and interactions between some or all sources [13,18,81,85,111]. Seedling mortality of transplanted first-year oak seedlings (northern red oak, chestnut oak) at Coweeta was positively correlated with great laurel basal area, soil aluminum, and leaf herbivory. Oak seedling biomass and tissue C:N ratios were negatively correlated with great laurel basal area. The results indicate tree seedling establishment and growth are limited by shade beneath great laurel, and suggest the potential importance of herbivory and aluminum toxicity in great laurel thickets . Another Coweeta investigation found that great laurel had no significant effect on canopy tree species (red maple, yellow-poplar, northern red oak, chestnut oak, hickory) seed reaching the forest floor. Germination of tree seeds was also not reduced by leaves and substrates in the great laurel thicket. Seedling mortality, however, was 5 times higher in great laurel thickets than outside the thickets. Tree seedlings under great laurel were not nitrogen limited, and lack of tree seedling success was therefore attributed to light limitation, herbivory, and litter fall . The effects of light limitation and great laurel litter characteristics are discussed in more detail below.
Light attenuation: Other studies have also demonstrated the effects of great laurel on species richness, species diversity, and seedling regeneration. A study of canopy gaps at Coweeta found that the presence of great laurel affected these variables more than gaps did, reducing species richness and diversity and seedling establishment. Weak recruitment was attributed to both low seed availability and competition with the great laurel shrub understory, largely due to the attenuation of light. Outside the great laurel understory, gap formation increased light levels 2-fold; beneath great laurel light levels did not increase following gap formation . Most seedling inhibition by great laurel occurs after emergence and is attributed to substantially reduced light (50-80%) where great laurel thickets are present, compared to hardwood forest understory without shrubs . Clinton  studied great laurel subcanopies at Coweeta Hydrologic Laboratory and found light levels were 77% lower during the growing season and 70% lower in the dormant season in areas with great laurel compared to areas without. During the growing season, light levels beneath great laurel were <2% of full sun. These low-light environments are extremely limiting to regeneration of hardwood species . Another North Carolina study found that the presence of a great laurel thicket reduced the availability of light by 80%, the frequency and duration of sunflecks (sudden, short-term increases in light intensity) by 96%, the availability of water by 20%, and the availability of several soil nutrients by variable amounts . Additional studies have demonstrated that while great laurel reduces light sufficiently to prevent the regeneration of tree seedlings such as northern red oak and black cherry (Prunus serotina), there is enough heterogeneity in the light to suggest that the deep shade only partially explains the complete inhibition of regenerating canopy trees under great laurel .
Litter characteristics: Inhibition of canopy tree seedlings is exacerbated by competition for soil water, nitrogen, and phosphorus , thick accumulations of litter, potential loss of mycorrhizal benefits, and inhibition of soil fauna.
Great laurel litter is slow to decompose [13,111], and the thick litter may inhibit tree seedling establishment . One study of plant litter at Coweeta Hydrologic Laboratory compared great laurel litter to that of yellow-poplar and chestnut oak and found significantly more (α=0.05) great laurel litter mass retained after 1 year . When newly germinated tree seedlings were found in a Southern Appalachian great laurel understory, they preferentially occurred in microsites with mineral soil, suggesting that great laurel litter suppresses seedling recruitment . However, other studies have found that leachates from great laurel leaves, litter, humus, or throughfall had no ecologically significant toxicity , and alleopathic effect is not an important inhibitor of black cherry or northern red oak seedling survival in great laurel thickets . Allelochemicals in great laurel litter can depress growth of some ectomycorrhizal species and reduce soil nutrient availability, therefore indirectly reducing canopy tree seedling survival . A Coweeta-based study found great laurel on study plots reduced mycorrhizal colonization of eastern hemlock seedlings after the first year; results showed 62% colonization on plots without great laurel compared to 19% on plots with great laurel present .
Hoover and Crossley  demonstrated that microarthropod abundance was significantly lower (α=0.05) in great laurel litter than in yellow-poplar and chestnut oak litter. Great laurel litter also depresses earthworm activity [13,111]. A study done in Kentucky found significantly fewer (P<0.01) earthworms in the mineral soil under both eastern hemlock and yellow-poplar trees with a great laurel understory than under the same tree species without a great laurel understory . The authors hypothesized that the lower earthworm density is likely due to phenolics or other chemicals leached from great laurel litter, foliage, and roots . Slow decomposition and reduced soil fauna facilitate the development of a thick forest floor which may give competitive advantage to great laurel seedlings over other understory vegetation [13,111].
Due to great laurel's preference for low pH soils, efforts at control have included
the addition of of limestone to increase soil pH. However, over 5 years, limestone applications
did not change pH below 1-inch (2.5 cm) depths and had no effect on great laurel growth
. Sprouts may be suppressed with 2,4-D [35,104,128], and the use of surfactants may
improve foliar herbicide uptake and efficiency . Picloram may also be useful in
controlling great laurel .
1. Adams, Harold S.; Stephenson, Steven L. 1989. Old-growth red spruce communities in the mid-Appalachians. Vegetatio. 85: 45-56. 
2. Allard, H. A.; Leonard, E. C. 1952. The Canaan and the Stony River Valleys of West Virginia, their former magnificent spruce forests, their vegetation and floristics today. Castanea. 17(1): 1-60. 
3. Arora, Rajeev; Lim, Chon-Chong; Krebs, Steven L.; Marian, Calin O. 2003. A genetic and physiological study of Rhododendron cold hardiness. In: Argent, George; McFarlane, Marjory, eds. Rhododendrons in horticulture and science: International Rhododendron conference: Proceedings; 2002; Edinburgh, UK. Edinburgh, UK: Royal Botanic Garden Edinburgh: 208-217. 
4. Baker, T. T.; Van Lear, D. H. 1998. Relations between density of rhododendron thickets and diversity of riparian forests. Forest Ecology and Management. 109: 21-32. 
5. Barringer, Kerry; Pannaman, Laura. 2003. Vascular plants of the Fairview Lake watershed, Sussex County, New Jersey. Journal of the Torrey Botanical Society. 130(1): 47-54. 
6. Baskin, Carol C.; Baskin, Jerry M. 2001. Seeds: ecology, biogeography, and evolution of dormancy and germination. San Diego, CA: Academic Press. 666 p. 
7. Beckage, Brian; Clark, James S. 2005. Does predation contribute to tree diversity? Oecologia. 143: 458-469. 
8. Beckage, Brian; Clark, James S.; Clinton, Barton D.; Haines, Bruce L. 2000. A long-term study of tree seedling recruitment in southern Appalachian forests: the effects of canopy gaps and shrub understories. Canadian Journal of Forest Research. 30(10): 1617-1631. 
9. Beckage, Brian; Lavine, Michael; Clark, James S. 2005. Survival of tree seedlings across space and time: estimates from long-term count data. Journal of Ecology. 93(6): 1177-1184. 
10. Beier, Colin M.; Horton, Jonathan L.; Walker, John F.; Clinton, Barton D.; Nilsen, Erik T. 2005. Carbon limitation leads to suppression of first year oak seedlings beneath evergreen understory shrubs in southern Appalachian hardwood forests. Plant Ecology. 176: 131-142. 
11. Blazich, Frank A.; Warren, Stuart L.; Acedo, Juan R.; Reece, William M. 1991. Seed germination of Rhododendron catawbiense and Rhododendron maximum: influence of light and temperature. Journal of Environmental Horticulture. 9(1): 5-8. 
12. Boettcher, S. E.; Kalisz, P. J. 1990. Single-tree influence on soil properties in the mountains of eastern Kentucky. Ecology. 71(4): 1365-1372. 
13. Boettcher, S. E.; Kalisz, P. J. 1991. Single-tree influence on earthworms in forest soils in eastern Kentucky. Soil Science Society of America Journal. 55(3): 862-865. 
14. Bratton, Susan Power; Meier, Albert J. 1998. The recent vegetation disturbance history of the Chattooga River watershed. Castanea. 63(3): 372-381. 
15. Braun, E. Lucy. 1989. The woody plants of Ohio. Columbus, OH: Ohio State University Press. 362 p. 
16. Carvell, K. L.; Tryon, E. H. 1959. Herbaceous vegetation and shrubs characteristic of oak sites in West Virginia. Castanea. 24: 39-43. 
17. Clinton, Barton D. 1995. Temporal variation in photosynthetically active radiation (PAR) in mesic southern Appalachian hardwood forest with and without Rhododendron understories. In: Gottschalk, Kurt W.; Fosbroke, Sandra L., eds. Proceedings, 10th central hardwood forest conference; 1995 March 5-8; Morgantown, WV. Gen. Tech. Rep. NE-197. Radnor, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station: 534-540. 
18. Clinton, Barton D. 2004. Rhododendron maximum. In: Francis, John K., ed. Wildland shrubs of the United States and its territories: thamnic descriptions: volume 1. Gen. Tech. Rep. IITF-GTR-26. San Juan, PR: U.S. Department of Agriculture, Forest Service, International Institute of Tropical Forestry; Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 623-624. 
19. Clinton, Barton D.; Boring, Lindsay R.; Swank, Wayne T. 1994. Regeneration patterns in canopy gaps of mixed-oak forests of the southern Appalachians: influences of topographic position and evergreen understory. The American Midland Naturalist. 132: 308-319. 
20. Clinton, Barton D.; Vose, James M. 1996. Effects of Rhododendron maximum L. on Acer rubrum L. seedling establishment. Castanea. 61(1): 38-45. 
21. Coddington, Jonathan; Field, Katharine G. 1978. Rare and endangered vascular plant species in Massachusetts. Cambridge, MA: New England Botanical Club. 52 p. 
22. Conover, M. R.; Kania, G. S. 1988. Browsing preference of white-tailed deer for different ornamental species. Wildlife Society Bulletin. 16: 175-179. 
23. Cooper, S. D.; McGraw, J. B. 1988. Constraints on reproductive potential at the level of the shoot module in three ericaceous shrubs. Functional Ecology. 2: 97-108. 
24. Copeland, Herbert F. 1943. A study, anatomical and taxonomic, of the genera of Rhododendroideae. The American Midland Naturalist. 30(3): 533-625. 
25. Czekalski, M. L. 1988. Propagation of Rhododendron maximum and Rhododendron smirnowii by stem cuttings. Acta Horticulturae. 226(2): 573-576. 
26. Davis, John H., Jr. 1930. Vegetation of the Black Mountains of North Carolina: an ecological study. Journal of the Elisha Mitchell Scientific Society. 29: 291-318. 
27. Day, Frank P., Jr.; Monk, Carl D. 1977. Seasonal nutrient dynamics in the vegetation on a southern Appalachian watershed. American Journal of Botany. 64(9): 1126-1139. 
28. Della-Bianca, Lino. 1980. White pine-chestnut oak. In: Eyre, F. H., ed. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters: 28-29. 
29. Della-Bianca, Lino. 1990. Pinus pungens Lamb. Table Mountain pine. In: Burns, Russell M.; Honkala, Barbara H., technical coordinators. Silvics of North America. Volume 1. Conifers. Agric. Handb. 654. Washington, DC: U.S. Department of Agriculture, Forest Service: 425-432. 
30. Della-Bianca, Lino; McGee, Charles E. 1972. Reaction of natural Rhododendron maximum L. to liming in the southern Appalachians. Journal of the Elisha Mitchell Scientific Society. 88(3): 109-112. 
31. Dibble, Alison C.; Campbell, Christopher S.; Tyler, Harry R., Jr.; Vickery, Barbara St. J. 1989. Maine's official list of endangered and threatened plants. Rhodora. 91(867): 244-269. 
32. Dighton, John; Coleman, David C. 1992. Phosphorus relations of roots and mycorrhizas of Rhododendron maximum L. in the Southern Appalachians, North Carolina. Mycorrhiza. 1(4): 175-184. 
33. Dobbs, M. M.; Parker, A. J. 2004. Evergreen understory dynamics in Coweeta Forest, North Carolina. Physical Geography. 25(6): 481-498. 
34. Duncan, Patricia J.; Bilderback, T. E. 1982. Effects of irrigation systems, gibberellic acid, and photoperiod on seed germination of Kalmia latifolia L. and Rhododendron maximum L. Hortscience. 17(6): 916-917. 
35. Elliott, Katherine J.; Boring, Lindsay R.; Swank, Wayne T. 1998. Changes in vegetation structure and diversity after grass-to-forest succession in a southern Appalachian watershed. The American Midland Naturalist. 140(2): 219-232. 
36. Elliott, Katherine J.; Hendrick, Ronald L.; Major, Amy E.; Vose, James M.; Swank, Wayne T. 1999. Vegetation dynamics after a prescribed fire in the southern Appalachians. Forest Ecology and Management. 114(2-3): 199-213. 
37. Esen, D.; Zedaker, S. M. 1999. Surfactants affect foliar uptake and translocation of triclopyr and imazapyr in Rhododendron. Proceedings, Southern Weed Science Society. 52: 126-127. 
38. Fisher, Cindy. 1995. Horse care: perilous pasture plants. Rural Heritage. 20(2): 44-45. 
39. Fleming, G. P.; Coulling, P. P.; Patterson, K. D. 2005. Palustrine system, [Online]. In: The natural communities of Virginia: Classification of ecological community groups. Second approximation. Version 2.1. Richmond, VA: Virginia Department of Conservation and Recreation, Division of Natural Heritage (Producer). Available: http://www.dcr.virginia.gov/dnh/ncintro.htm [2005, November 3]. 
40. Fleming, G. P.; Coulling, P. P.; Patterson, K. D. 2005. Terrestrial system, [Online]. In: The natural communities of Virginia: Classification of ecological community groups. Second approximation. Version 2.1. Richmond, VA: Virginia Department of Conservation and Recreation, Division of Natural Heritage (Producer). Available: http://www.dcr.virginia.gov/dnh/ncintro.htm [2005, November 3]. 
41. Flora of North America Association. 2008. Flora of North America: The flora, [Online]. Flora of North America Association (Producer). Available: http://www.fna.org/FNA. 
42. Forbes, E. B.; Bechdel, S. I. 1931. Mountain laurel and rhododendron as foods for the white tailed deer. Ecology. 12(2): 323-333. 
43. Ford, William M.; Menzel, M. Alex; McGill, David W.; Laerm, Joshua; McCay, Timothy S. 1999. Effects of a community restoration fire on small mammals and herpetofauna in the southern Appalachians. Forest Ecology and Management. 114(2-3): 233-243. 
44. Gleason, Henry A.; Cronquist, Arthur. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. 2nd ed. New York: New York Botanical Garden. 910 p. 
45. Glenn, Christopher T.; Blazich, Frank A.; Warren, Stuart L. 1998. Influence of storage temperatures on long-term seed viability of selected native ericaceous species. Journal of Environmental Horticulture. 16(3): 166-172. 
46. Glenn, Christopher T.; Blazich, Frank A.; Warren, Stuart L. 1999. Secondary seed dormancy of Rhododendron catawbiense and Rhododendron maximum. Journal of Environmental Horticulture. 17(1): 1-4. 
47. Glover, Fred A. 1948. Winter activities of wild turkey in West Virginia. Journal of Wildlife Management. 12(4): 416-427. 
48. Goslee, S. C.; Brooks, R. P.; Cole, C. A. 1997. Plants as indicators of wetland water source. Plant Ecology. 131(2): 199-206. 
49. Hanlon, Teresa J.; Williams, Charles E.; Moriarity, William J. 1998. Species composition of soil seed banks of Allegheny Plateau riparian forests. Journal of the Torrey Botanical Society. 125(3): 199-215. 
50. Hann, Wendel; Havlina, Doug; Shlisky, Ayn; [and others]. 2005. Interagency fire regime condition class guidebook. Version 1.2, [Online]. In: Interagency fire regime condition class website. U.S. Department of Agriculture, Forest Service; U.S. Department of the Interior; The Nature Conservancy; Systems for Environmental Management (Producer). Variously paginated [+ appendices]. Available: http://www.frcc.gov/docs/22.214.171.124/Complete_Guidebook_V1.2.pdf [2007, May 23]. 
51. Harlow, Richard F.; Whelan, James B.; Crawford, Hewlette S.; Skeen, John E. 1975. Deer foods during years of oak mast abundance and scarcity. Journal of Wildlife Management. 39(2): 330-336. 
52. Hedman, Criag W.; Van Lear, David H. 1995. Vegetative structure and composition of southern Appalachian forests. Bulletin of the Torrey Botanical Club. 122(2): 134-144. 
53. Hille Ris Lambers, Janneke; Clark, James S. 2003. Effects of dispersal, shrubs, and density-dependent mortality on seed and seedling distributions in temperate forests. Canadian Journal of Forest Research. 33(5): 783-795. 
54. Hille Ris Lambers, Janneke; Clark, James S. 2005. The benefits of seed banking for red maple (Acer rubrum): maximizing seedling recruitment. Canadian Journal of Forest Research. 35: 806-813. 
55. Hille Ris Lambers, Janneke; Clark, James S.; Lavine, Michael. 2005. Implications of seed banking for recruitment of southern Appalachian woody species. Ecology. 86(1): 85-95. 
56. Hooper, Ralph M. 1969. Prescribed burning for laurel and rhododendron control in the southern Appalachians. Res. Note SE-116. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southeastern Forest Experiment Station. 6 p. 
57. Hooper, Robert G. 1978. Cove forests: bird communities and management options. In: DeGraaf, Richard M., tech. coord. Proceedings of the workshop management of southern forests for nongame birds; 1978 January 24-26; Atlanta, GA. Gen. Tech. Rep. SE-14. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southeastern Forest Experiment Station: 90-97. 
58. Hoover, Coeli M.; Crossley, D. A., Jr. 1995. Leaf litter decomposition and microarthropod abundance along an altitudinal gradient. In: Collins, H. P., Robertson, G. P.; Klug, M. J., eds. The significance and regulation of soil biodiversity. Dordrecht, The Netherlands: Kluwer Academic Publishers: 287-292. 
59. Iles, J. K.; Beattie, D. J.; Kuhns, L. J. 1990. Rooting hardwood cuttings in poly-huts. Applied Agricultural Research. 5(4): 298-301. 
60. Johnson, A. Sydney; Hale, Philip E.; Ford, William M.; Wentworth, James M.; French, Jeffrey R.; Anderson, Owen F.; Pullen, Gerald B. 1995. White-tailed deer foraging in relation to successional stage, overstory type and management of southern Appalachian forests. The American Midland Naturalist. 133(1): 18-35. 
61. Kartesz, John T. 1999. A synonymized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. 1st ed. In: Kartesz, John T.; Meacham, Christopher A. Synthesis of the North American flora (Windows Version 1.0), [CD-ROM]. Chapel Hill, NC: North Carolina Botanical Garden (Producer). In cooperation with: The Nature Conservancy; U.S. Department of Agriculture, Natural Resources Conservation Service; U.S. Department of the Interior, Fish and Wildlife Service. 
62. Korstian, Clarence F. 1937. Perpetuation of spruce on cut-over and burned lands in the higher Southern Appalachian Mountains. Ecological Monographs. 7(1): 125-167. 
63. Laderman, Aimlee D.; Golet, Francis C.; Sorrie, Bruce A.; Woolsey, Henry L. 1987. Atlantic white cedar in the glaciated Northeast. In: Laderman, Aimlee D., ed. Atlantic white cedar wetlands symposium; 1984 October 9-11; Woods Hole, MA. Boulder, CO: Westview Press: 19-34. 
64. LANDFIRE Rapid Assessment. 2005. Reference condition modeling manual (Version 2.1), [Online]. In: LANDFIRE. Cooperative Agreement 04-CA-11132543-189. Boulder, CO: The Nature Conservancy; U.S. Department of Agriculture, Forest Service; U.S. Department of the Interior (Producers). 72 p. Available: http://www.landfire.gov/downloadfile.php?file=RA_Modeling_Manual_v2_1.pdf [2007, May 24]. 
65. LANDFIRE Rapid Assessment. 2007. Rapid assessment reference condition models. In: LANDFIRE. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Lab; U.S. Geological Survey; The Nature Conservancy (Producers). Available: http://www.landfire.gov/models_EW.php 
66. Leach, David G. 1963. Rhododendrons of the world and how to grow them. New York: Charles Scribner's Sons. 544 p. 
67. Lei, T. T.; Nilsen, E. T.; Semones, S. W. 2006. Light environment under Rhododendron maximum thickets and estimated carbon gain of regenerating forest tree seedlings. Plant Ecology. 184: 143-156. 
68. Lei, Thomas T.; Semones, Shawn W.; Walker, John F.; Clinton, Barton D.; Nilsen, Erik T. 2002. Effects of Rhododendron maximum thickets on tree seed dispersal, seedling morphology, and survivorship. International Journal of Plant Science. 163(6): 991-1000. 
69. Lipscomb, M. V.; Nilsen, E. T. 1990. Environmental and physiological factors influencing the natural distribution of evergreen and deciduous ericaceous shrubs on northeast and southwest facing slopes of the southern Appalachian Mountains. I. Irradiance tolerance. American Journal of Botany. 77(1): 108-115. 
70. Lipscomb, M. V.; Nilsen, E. T. 1990. Environmental and physiological factors influencing the natural distribution of evergreen and deciduous ericaceous shrubs on northeast and southwest facing slopes of the southern Appalachian Mountains. II. Water relations. American Journal of Botany. 77(4): 517-526. 
71. Little, Elbert L., Jr. 1977. Atlas of United States trees. Volume 4. Minor eastern hardwoods. Misc. Pub. No. 1342. Washington, DC: U.S. Department of Agriculture, Forest Service. 17 p. 
72. Little, Parker L. 2002. An exploration and study of White Rock Mountain, WV for unusual forms of Rhododendron species. American Rhododendron Society Journal. 56(3): 122-131. 
73. Maine Department of Conservation, Natural Resources Information Mapping Center. 1999. Maine Natural Areas Program: Official list of endangered and threatened plants in Maine, [Online]. Available: Http://www.state.me.us/doc/nrimc/mnap/factsheets/snameindex.htm [2001, October 11]. 
74. Martin, Alexander C.; Zim, Herbert S.; Nelson, Arnold L. 1951. American wildlife and plants. New York: McGraw-Hill Book Company, Inc. 500 p. 
75. Martin, William H. 1990. The role and history of fire in the Daniel Boone National Forest. Final Report. Winchester, KY: U.S. Department of Agriculture, Forest Service, Daniel Boone National Forest. 131 p. 
76. McGinty, Douglas T. 1972. The ecological roles of Kalmia latifolia L. and Rhododendron maximum L. in the hardwood forest at Coweeta. Athens, GA: University of Georgia. 81 p. Thesis. 
77. McLeod, Donald Evans. 1988. Vegetation patterns, floristics, and environmental relationships in the Black and Craggy Mountains of North Carolina. Chapel Hill, NC: University of North Carolina. 222 p. Dissertation. 
78. Monk, Carl D.; McGinty, Douglas T.; Day, Frank P., Jr. 1985. The ecological importance of Kalmia latifolia and Rhododendron maximum in the deciduous forest of the southern Appalachians. Bulletin of the Torrey Botanical Club. 112(2): 187-193. 
79. Mou, Pu; Warrillow, Michael P. 2000. Ice storm damage to a mixed hardwood forest and its impacts on forest regeneration in the ridge and valley region of southwestern Virginia. Journal of the Torrey Botanical Society. 127(1): 66-82. 
80. Neary, D. G.; Douglass, J. E.; Ruehle, J. L.; Fox, W. 1984. Converting rhododendron-laurel thickets to white pine with picloram and mycorrhizae-inoculated seedlings. Southern Journal of Applied Forestry. 8(3): 163-168. 
81. Nilsen, E. T.; Clinton, B. D.; Lei, T. T.; Miller, O. K.; Semones, S. W.; Walker, J. F. 2001. Does Rhododendron maximum L. (Ericaceae) reduce the availability of resources above and belowground for canopy tree seedlings? The American Midland Naturalist. 145(2): 325-343. 
82. Nilsen, E. T.; Stetler, D. A.; Gassman, C. A. 1988. Influence of age and microclimate on the photochemistry of Rhododendron maximum leaves. II. Chloroplast structure and photosynthetic light response. American Journal of Botany. 75(10): 1526-1534. 
83. Nilsen, Erik T.; Horton, Jonathan. 2003. Rhododendron maximum in the USA: similarities to Rhododendron ponticum in Britain and ecological mechanisms for community effects. In: Argent, George; McFarlane, Marjory, eds. Rhododendrons in horticulture and science: International Rhododendron conference: Proceedings; 2002; Edinburgh, UK. Edinburgh, UK: Royal Botanic Garden Edinburgh: 259-272. 
84. Nilsen, Erik T.; Sharifi, M. R.; Rundel, P. W. 1987. Leaf dynamics in an evergreen and a deciduous species with even-aged leaf cohorts, from different environments. The American Midland Naturalist. 118(1): 46-55. 
85. Nilsen, Erik T.; Walker, John F.; Miller, Orson K.; Semones, Shawn W.; Lei, Thomas T.; Clinton, Barton D. 1999. Inhibition of seedling survival under Rhododendron maximum (Ericaceae): could allelopathy be a cause? American Journal of Botany. 86(11): 1597-1605. 
86. Nilsen, Erik Tallak. 1986. Quantitative phenology and leaf survivorship of Rhododendron maximum in contrasting irradiance environments of the southern Appalachian Mountains. American Journal of Botany. 73(6): 822-831. 
87. Nowacki, Gregory J.; Abrams, Marc D. 1994. Forest composition, structure, and disturbance history of the Alan Seeger Natural Area, Huntington County, Pennsylvania. Bulletin of the Torrey Botanical Club. 121(3): 277-291. 
88. Oosting, Henry J.; Bourdeau, Philippe F. 1955. Virgin hemlock forest segregates in the Joyce Kilmer Memorial Forest of western North Carolina. Botanical Gazette. 116(4): 340-359. 
89. Phillips, Donald L.; Murdy, William H. 1985. Effects of Rhododendron (Rhododendron maximum L.) on regeneration of southern Appalachian hardwoods. Forest Science. 31(1): 226-233. 
90. Plocher, Allen E. 1984. Age distribution and population dynamics of Rhododendron maximum thickets in north central West Virginia. Morgantown, WV: West Virginia University. 76 p. Thesis. 
91. Plocher, Allen E.; Carvell, Kenneth L. 1987. Population dynamics of rosebay rhododendron thickets in the southern Appalachians. Bulletin of the Torrey Botanical Club. 114(2): 121-126. 
92. Radford, Albert E.; Ahles, Harry E.; Bell, C. Ritchie. 1968. Manual of the vascular flora of the Carolinas. Chapel Hill, NC: The University of North Carolina Press. 1183 p. 
93. Raunkiaer, C. 1934. The life forms of plants and statistical plant geography. Oxford: Clarendon Press. 632 p. 
94. Reilly, Matthew J.; Wimberly, Michael C.; Newell, Claire L. 2006. Wildfire effects on plant species richness at multiple spatial scales in forest communities of the southern Appalachians. Journal of Ecology. 94(1): 118-130. 
95. Rivers, Christopher T.; Van Lear, David H.; Clinton, Barton D.; Waldrop, Thomas A. 1999. Community composition in canopy gaps as influenced by presence or absence of Rhododendron maximum. In: Haywood, James D., ed. Proceedings, 10th biennial southern silvicultural research conference; 1999 February 16-18; Shreveport, LA. Gen. Tech. Rep. SRS-30. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station: 57-60. 
96. Rivers, Christopher Todd. 1999. Community composition in canopy gaps as influenced by Rhododendron maximum. Clemson, SC: Clemson University. 75 p. Thesis. 
97. Robinette, Sadie L. 1974. Rhododendron. In: Gill, John D.; Healy, William M. Shrubs and vines for northeastern wildlife. Gen. Tech. Rep. NE-9. Upper Darby, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station: 113-115. 
98. Romancier, Robert M. 1971. Combining fire and chemicals for the control of rhododondron thickets. Res. Note SE-149. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southeastern Forest and Range Experiment Station. 7 p. 
99. Romancier, Robert M. 1971. Ecology of the seedling establishment of Rhododendron maximum L. in the southern Appalachians. Durham, NC: Duke University. 189 p. Dissertation. 
100. Rowan, Ella L.; Ford, W. Mark; Castleberry, Steven B.; Rodrigue, Jane L.; Schuler, Thomas M. 2005. Response of eastern chipmunks to single application spring prescribed fires on the Fernow Experimental Forest. Res. Pap. NE-727. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station. 10 p. Available: http://www.fs.fed.us/ne/newtown_square/publications/research_papers/pdfs/2005/ne_rp727.pdf [2006 February 1]. 
101. Sakai, A.; Fuchigami, L.; Weiser, C. J. 1986. Cold hardiness in the genus Rhododendron. Journal of the American Society for Horticultural Science. 111(2): 273-280. 
102. Schafale, Michael P.; Weakley, Alan S. 1990. Classification of the natural communities of North Carolina: 3rd approximation. Raleigh, NC: Department of Environment, Health, and Natural Resources, Division of Parks and Recreation, North Carolina Natural Heritage Program. 325 p. Available online: http://ils.unc.edu/parkproject/nhp/publications/class.pdf [2005, February 14]. 
103. Seymour, Frank Conkling. 1982. The flora of New England. 2nd ed. Phytologia Memoirs 5. Plainfield, NJ: Harold N. Moldenke and Alma L. Moldenke. 611 p. 
104. Sluder, Earl R. 1958. Control of cull trees and weed species in hardwood stands. Stn. Pap. 95. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southeastern Forest Experiment Station. 13 p. 
105. Spencer, Ernest L. 1932. Natural distribution of Rhododendron maximum in New Jersey. Bulletin of the Torrey Botanical Club. 59(7): 401-414. 
106. Starrett, Mark C.; Blazich, Frank A.; Warren, Stuart L. 1993. Initial growth of rosebay rhododendron seedlings as influenced by day and night temperatures. Hortscience. 28(7): 705-707. 
107. Stickney, Peter F. 1989. Seral origin of species comprising secondary plant succession in Northern Rocky Mountain forests. FEIS workshop: Postfire regeneration. Unpublished draft on file at: U.S. Department of Agriculture, Forest Service, Intermountain Research Station, Fire Sciences Laboratory, Missoula, MT. 10 p. 
108. Strausbaugh, P. D.; Core, Earl L. 1977. Flora of West Virginia. 2nd ed. Morgantown, WV: Seneca Books, Inc. 1079 p. 
109. Tyler, Harry R., Jr. 1975. Great rhododendron, Rholodendron maximum, in Maine and its relevance to the Critical Areas Program. Planning Report Number 3. Augusta, ME: Maine State Planning Office, Natural Resource Planning Division, Critical Areas Program. 17 p. 
110. U.S. Department of Agriculture, Natural Resources Conservation Service. 2008. PLANTS Database, [Online]. Available: http://plants.usda.gov/. 
111. Van Breemen, Nico; Finzi, Adrien C. 1998. Plant-soil interactions: ecological aspects and evolutionary implications. Biogeochemistry. 42(1/2): 1-19. 
112. Van Lear, D. H.; Vandermast, D. B.; Rivers, C. T.; Baker, T. T.; Hedman, C. W.; Clinton, D. B.; Waldrop, T. A. 2002. American chestnut, rhododendron, and the future of Appalachian cove forests. In: Outcalt, Kenneth W., ed. Proceedings, 11th biennial southern silvicultural research conference; 2001 March 20-22; Knoxville, TN. Gen. Tech. Rep. SRS-48. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station: 214-220. 
113. Van Lear, David H. 2000. Fire and silviculture: Recent advances in the silvicultural use of prescribed fire. In: Moser, W. Keith; Moser, Cynthia F., eds. Fire and forest ecology: innovative silviculture and vegetation management: Proceedings of the 21st Tall Timbers fire ecology conference: an international symposium; 1998 April 14-16; Tallahassee, FL. No. 21. Tallahassee, FL: Tall Timbers Research, Inc: 183-189. 
114. Vandermast, D. B.; Van Lear, D. H.; Clinton, B. D. 2002. American chestnut as an allelopath in the southern Appalachians. Forest Ecology and Management. 165: 173-181. 
115. Vandermast, David B.; Van Lear, David H. 1999. Vegetative composition of riparian forest once dominated by American chestnut. In: Haywood, James D., ed. Proceedings, 10th biennial southern silvicultural research conference; 1999 February 16-18; Shreveport, LA. Gen. Tech. Rep. SRS-30. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station: 3-7. 
116. Walbridge, Mark R.; Lang, Gerald E. 1982. Major plant communities and patterns of community distribution in four wetlands of the unglaciated Appalachian region. In: McDonald, Brian R., ed. Proceedings, symposium on wetlands of the unglaciated Appalachian region; 1982 May 26-28; Morgantown, WV. Morgantown, WV: West Virginia University: 131-142. 
117. Walker, John F.; Miller, Orson K., Jr.; Lei, Tom; Semones, Shawn; Nilsen, Erik; Clinton, B. D. 1999. Suppression of ecotomycorrhizae on canopy tree seedlings in Rhododendron maximum L. (Ericaceae) thickets in the southern Appalachians. Mycorrhiza. 9(1): 49-56. 
118. Weaver, Keith M. 2000. Black bear ecology and the use of prescribed fire to enhance bear habitat. In: Yaussy, Daniel A., compiler. Proceedings: workshop on fire, people, and the central hardwoods landscape; 2000 March 12-14; Richmond, KY. Gen. Tech. Rep. NE-274. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station: 89-96. 
119. White, Peter S.; Buckner, Edward R.; Pittillo, J. Dan; Cogbill, Charles V. 1993. High-elevation forests: spruce-fir forests, northern hardwood forests, and associated communities. In: Martin, William H.; Boyce, Stephen G.; Echternacht, Arthur C., eds. Biodiversity of the southeastern United States: Upland terrestrial communities. New York: John Wiley & Sons, Inc: 305-337. 
120. Whittaker, R. H. 1956. Vegetation of the Great Smoky Mountains. Ecological Monographs. 26(1): 1-79. 
121. Whittaker, R. H. 1962. Net production relations of shrubs in the Great Smoky Mountains. Ecology. 43(3): 357-377. 
122. Whittaker, R. H. 1963. Net production of heath balds and forest heaths in the Great Smoky Mountains. Ecology. 44(1): 176-182. 
123. Widrlechner, Mark P.; Larson, Richard A.; Dragula, Sharon K. 1993. Exploring the deciduous azaleas and elepidote rhododendrons of the midwestern United States. Journal of American Rhododendron Society. 47(3): 153-156. 
124. Williams, Ross F.; Bilderback, Theodore E. 1980. Factors affecting rooting of Rhododendron maximum and Kalmia latifolia stem cuttings. Hortscience. 15(6): 827-828. 
125. Williams, Ross Freeman. 1979. Rooting response of Rhododendron maximum L. and Kalmia latifolia L. stem cuttings to hormones, medium fertility, source, and propagating structures. Raleigh, NC: North Carolina State University. 43 p. Thesis. 
126. Wofford, B. Eugene. 1989. Guide to the vascular plants of the Blue Ridge. Athens, GA: The University of Georgia Press. 384 p. 
127. Woods, Frank W.; Shanks, Royal E. 1959. Natural replacement of chestnut by other species in the Great Smoky Mountains National Park. Ecology. 40(3): 349-361. 
128. Yawney, Harry W. 1962. Control of rhododendron by basal spray. Res. Note No. 132. Upper Darby, PA: U.S. Department of Agriculture, Forest Service, Northeast Forest Experiment Station. 7 p. 
129. Yoke, Kathleen A.; Rennie, John C. 1996. Landscape ecosystem classification in the Cherokee National Forest, east Tennessee, U.S.A. Environmental Monitoring and Assessment. 39(1-3): 323-338.