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SPECIES:  Kalmia angustifolia
Sheep laurel in bloom. Wikimedia Commons image by Jomegat.

Introductory

SPECIES: Kalmia angustifolia
AUTHORSHIP AND CITATION: Van Deelen, Timothy R. 1991. Kalmia angustifolia. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/shrub/kalang/all.html []. Revisions: Images were added on 17 July 2018.
ABBREVIATION: KALANG SYNONYMS: Kalmia angustifolia forma candida Fernald [43] NRCS PLANT CODE: KAAN COMMON NAMES: sheep laurel lambkill sheepkill calfkill dwarf-laurel wicky TAXONOMY: The scientific name of sheep laurel is Kalmia angustifolia L. (Ericaceae). Sheep laurel does not hybridize with other North American Kalmia species [43]. LIFE FORM: Shrub FEDERAL LEGAL STATUS: No special status OTHER STATUS: NO-ENTRY


DISTRIBUTION AND OCCURRENCE

SPECIES: Kalmia angustifolia
GENERAL DISTRIBUTION: Sheep laurel is found in northeastern North America from Newfoundland and Labrador west through Ontario, south through Michigan, and occasionally as far south as Georgia. It is most common in the eastern Great Lakes region, the St. Lawrence River region, northern New England, and the Maritime Provinces. Sheep laurel is occasional in the Appalachian Mountains, on the Piedmont Plateau, and on the United States' upper Atlantic Coastal Plain [36,41].
Distribution of sheep laurel. Map courtesy of USDA, NRCS. 2018. The PLANTS Database. National Plant Data Team, Greensboro, NC [2018, July 17] [40].
ECOSYSTEMS: 
   FRES10  White - red - jack pine
   FRES11  Spruce - fir
   FRES13  Loblolly - shortleaf pine
   FRES19  Aspen - birch


STATES: 
     CT  GA  ME  MD  MA  MI  MN  NH  NJ  NY
     PA  RI  VT  WI  LB  NB  NF  NS  ON  PE
     PQ



BLM PHYSIOGRAPHIC REGIONS: 
NO-ENTRY


KUCHLER PLANT ASSOCIATIONS: 
   K093  Great Lakes spruce - fir forest
   K094  Conifer bog
   K095  Great Lakes pine forest
   K096  Northeastern spruce - fir forest
   K106  Northern hardwoods
   K107  Northern hardwoods - fir forest
   K108  Northern hardwoods - spruce forest
   K110  Northeastern oak - pine forest  (Quercus-Pinus)


SAF COVER TYPES: 
     1  Jack pine
     5  Balsam fir
    12  Black spruce
    13  Black spruce - tamarack
    18  Paper birch
    21  Eastern white pine
    32  Red spruce
    33  Red spruce - balsam fir
    35  Paper birch - red spruce - balsam fir
    37  Northern white cedar
    45  Pitch pine
   107  White spruce


SRM (RANGELAND) COVER TYPES: 
NO-ENTRY


HABITAT TYPES AND PLANT COMMUNITIES: 
Sheep laurel is a common understory shrub in eastern lowland forests.
It is characteristically found in coniferous, mixed, and hardwood stands
in eastern Canada and the northeastern United States [28,38].  On
peatlands, it often occurs in extensive, nearly pure stands known as
"heaths" [6].  Sheep laurel is a common dominant of bog communities in
the lower St. Lawrence lowlands [10] and grows in the New Jersey Pine
Barrens [11].

Common overstory associates include red spruce (Picea rubens) [2], black
spruce (Picea mariana) [8,42], jack pine (Pinus banksiana) [28], quaking
aspen (Populus tremuloides), and paper birch (Betula papyrifera) [37].
Understory associates include bog Labrador tea (Ledum groenlandicum),
low sweet blueberry (Vaccinium angustifolium), wintergreen (Gaultheria
procumbens), sweet fern (Comptonia peregrina) [43], Sphagnum spp., and
Cladonia spp. [8,37]

Published classification schemes listing sheep laurel as a dominant or
codominant member of a plant associations or community types include:

Geographical changes in the vegetation of raised bogs in the bay of
   Fundy region of Maine and New Brunswick [7]
The principal plant associations of the St. Lawrence Valley [9].

MANAGEMENT CONSIDERATIONS

SPECIES: Kalmia angustifolia
IMPORTANCE TO LIVESTOCK AND WILDLIFE: Sheep laurel is poisonous to livestock; hence the common names sheepkill, lambkill, and calfkill [24,36,41]. Toxicity levels, defined as the percent body weight of foliage needed to induce toxic symptoms, are 0.15 percent for sheep, 0.20 percent for cattle, and 0.25 percent for goats [24]. Sheep laurel also poisons horses. Poisoning typically occurs during the winter when persistent sheep laurel leaves are the only available vegetation above light snow cover. Poisoning symptoms include salivation, watery eyes, running nose, vomiting with convulsions, and paralysis [43]. Sheep laurel is not eaten by moose in Newfoundland [39] although it is eaten by grouse [41], and is important winter food for caribou in Ontario [1]. PALATABILITY: Sheep laurel leaves are tough. Animals that eat them do so only when other forage is unavailable [43]. NUTRITIONAL VALUE: NO-ENTRY COVER VALUE: Sheep laurel provides nesting sites for willow ptarmigans [43]. VALUE FOR REHABILITATION OF DISTURBED SITES: Although used to reclaim mined peatlands [13], sheep laurel is little used for reclamation of other sites, so its value on other sites remains unknown. It responds to transplanting by sprouting [17]. It returns very little leaf litter to the soil. Sheep laurel builds up the raw humus layer through root die-off which may include 20 percent of the root mass greater than 0.33 inch (1 cm) in diameter and account for 9.2 tons of additional humus per acre (907 kg/ha) annually. It returns 19 pounds of nitrogen per acre (28 kg/ha) yearly [6]. Sheep laurel has a class IV gypsy-moth susceptibility: unfavored or rarely fed upon [20]. OTHER USES AND VALUES: NO-ENTRY OTHER MANAGEMENT CONSIDERATIONS: Sheep laurel is a serious pest in blueberry fields. Control by fire is usually ineffective [34]. Sheep laurel has stronger rhizomes and sprout growth than blueberry and requires repeated control [21]. Ten percent of all the low sweet blueberry acreage in the Maritime Provinces requires sheep laurel herbicide control treatment each year [43]. In addition to outcompeting conifer seedlings for nutrients, light, and space [29], sheep laurel has an allelopathic effect on conifer seedlings [5,29,39]. The establishment of sheep laurel-dominated heaths after disturbance may produce soil conditions that prevent conifer seedling establishment [5,6]. Several herbicide treatments have been tested for control of sheep laurel. Most were difficult to use and ineffective [43].

BOTANICAL AND ECOLOGICAL CHARACTERISTICS

SPECIES: Kalmia angustifolia
GENERAL BOTANICAL CHARACTERISTICS: Sheep laurel is a small, branchy, evergreen shrub which reaches 1 to 3 feet (30-90 cm) in height. It has pink, showy, five-part flowers on stalked clusters. The fruit is a small capsule containing many seeds. Capsules may persist on the branches for several years [4,36]. Sheep laurel forms a well-developed and closely interlacing network of rhizomes. The root system consists of a taproot which may extend to a depth of 3 feet (1 m) [43]. It also has fine roots nearer to the soil surface [6]. Fine root depths vary from 3.5 inches (9 cm) in mineral soil to 12 inches (31 cm) in bogs [14,39]. RAUNKIAER LIFE FORM: Phanerophyte REGENERATION PROCESSES: Reproduction is primarily vegetative. Sheep laurel plants are clonal and expand laterally. Sprouts grow from dormant buds on rhizomes. Very little is known about sexual reproduction and seedling establishment. Individual stems produce an estimated 7,100 seeds per year. Clones are self-compatible, but seedlings from selfing are less vigorous than seedlings from crossing [43]. SITE CHARACTERISTICS: Sheep laurel grows on a variety of sites ranging from wet sphagnum bogs to dry jack pine forests. It is frequently found on sites that are very dry during the summer but saturated or flooded during the spring [34]. On peatland, it grows under both oligotrophic and ombrotrophic conditions [3,8]. In the Northeast, sheep laurel grows in moist conifer woods, pastures, barrens, roadsides, and open thickets [34]. Sheep laurel typically grows on podzols which have developed under a cold to temperate climate on acidic parent material [43]. On peatland it grows on well-drained peat and peaty podzols. On forested sites sheep laurel grows on dry, acid, run-out soils; rocky, gravelly soils; sandy loams; and iron-rich, lithosolic, or Ortstein podzols [7,34,36]. Its western range may be limited by high soil pH and lack of moisture [43]. On peatlands in Newfoundland, sheep laurel grows independent of the mineral soil, taking all of its nutrients from the organic layer. On forested sites it roots in mineral soil [6]. Sheep laurel grows under a climate regime that is cold and wet for much of the year. Minimum temperatures at the northern limits of its range are -40 degrees Fahrenheit (-40 deg C) [43]. SUCCESSIONAL STATUS: Sheep laurel is somewhat shade intolerant. Under low light conditions it persists but does not grow appreciably. Overstory removal and increased light trigger release, causing sheep laurel cover to quickly increase [3]. It is considered early successional in the bog formation sequence, although it may become dominant and arrest succession following bog disturbance by fire or drainage [6]. On frequently disturbed forest sites, most logging practices favor sheep laurel establishment. Clones may expand and persist for several decades, reducing tree establishment and creating heaths or "Kalmia barrens" [5,6,32]. On undisturbed sites sheep laurel is replaced by trees such as balsam fir and black spruce [5]. SEASONAL DEVELOPMENT: Sheep laurel flowers during June and early July. Its fruit ripens between late July and mid-September [23,36,43]. The seeds disperse in early October. New shoot growth begins during late May and early June [43].

FIRE ECOLOGY

SPECIES: Kalmia angustifolia
FIRE ECOLOGY OR ADAPTATIONS: Sheep laurel sprouts soon after fire [35]. Persistent rhizomes in the soil are protected from all but the most severe fires and allow it to regenerate quickly [15,35]. FIRE REGIMES: Find 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". POSTFIRE REGENERATION STRATEGY: Small shrub, adventitious-bud root crown

FIRE EFFECTS

SPECIES: Kalmia angustifolia
IMMEDIATE FIRE EFFECT ON PLANT: Fire kills aerial portions of sheep laurel stems. Light fires that do not harm the buried rhizomes do not kill the plant. Severe fires that consume the organic layer or sufficiently heat the soil surrounding the rhizomes do kill sheep laurel [30]. DISCUSSION AND QUALIFICATION OF FIRE EFFECT: Sheep laurel's ability to survive a fire depends on the survival of its rhizomes. Sheep laurel rhizomes growing in forest mineral soils are relatively shallowly buried and depend on the insulating value of the soil and soil moisture for protection against lethal soil temperatures [16]. On bogs or peatlands, sheep laurel rhizomes are generally deeper. When wet, these soils offer both insulation and protection from fire. When dry, these organic soils themselves may be consumed, killing the sheep laurel rhizomes [15]. On peatlands, sheep laurel survives only where the humus layer is not destroyed [30]. PLANT RESPONSE TO FIRE: The immediate postfire response of sheep laurel is a decrease in frequency and abundance [18]. However, it quickly responds to fire (and cutting) with vigorous sprouting [29]. Fire stimulates the growth of adventitious roots from the burned root stubs and rhizomes near the soil surface [29,35]. Sprouts can be seen soon afterward. In an Ontario study, new shoots were 2 inches (5 cm) tall 2 weeks after a fire, and 6 inches tall (15 cm) 6 weeks after the fire [35]. DISCUSSION AND QUALIFICATION OF PLANT RESPONSE: Although visible on a site within 2 weeks of a fire, sheep laurel shows the greatest increase in frequency between postfire year 1 and 2. Its frequency may increase 500 percent and then remain relatively constant for the next 40 years [31]. Regrowth after summer fires is slower than regrowth after spring or fall fires, which shows a strong increase in sprout density. Summer fires coincide with a period of low photosynthate reserves that follows the spring growth spurt [14,17]. Light spring or fall fires encourage prolific growth [31]. In a greenhouse experiment, Mallik [29] compared sheep laurel shrubs that had been cut or cut and burned with control plants. There was no significant difference between the number and density of new sprouts for the treatments and for the control. Treatment sprouts were more robust, but treatment rhizomes were smaller. Sheep laurel directs photosynthates to aboveground growth at the expense of belowground growth following disturbance. FIRE MANAGEMENT CONSIDERATIONS: All but the most severe fires enhance the growth of sheep laurel stands. Permanent control of sheep laurel require fires severe enough to kill the rhizomes; such fires often consume the organic layer of the soil [31]. Managers should note that most sheep laurel-dominated communities in Nova Scotia are associated with frequent fires. Logging and fire promote heath formation [5]. The high stem density in heaths causes severe fires when they eventually burn. Frequent fires reduce fuel accumulation and, consequently, are less severe [26].

REFERENCES

SPECIES: Kalmia angustifolia
REFERENCES: 1. Ahti, T.; Hepburn, T. L. 1967. Preliminary studies on woodland caribou range, especially on lichen stands, in Ontario. Res. Rep. (Wildlife) No. 74. Toronto, ON: Ontario Department of Lands and Forests, Research Branch. 134 p. [13294] 2. Blum, Barton M. 1990. Picea rubens Sarg. red spruce. 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: 250-259. [13388] 3. Brumelis, G.; Carleton, T. J. 1989. The vegetation of post-logged black spruce lowlands in central Canada. II. Understory vegetation. Journal of Applied Ecology. 26: 321-339. [7864] 4. Chapman, William K.; Bessette, Alan E. 1990. Trees and shrubs of the Adirondacks. Utica, NY: North Country Books, Inc. 131 p. [12766] 5. Damman, A. W. H. 1964. Some forest types of central Newfoundland and their relation to environmental factors. Forest Science Monograph 8. Washington, DC: Society of American Foresters. 62 p. [14281] 6. Damman, A. W. H. 1971. Effect of vegetation changes on the fertility of a Newfoundland forest site. Ecological Monographs. 41(3): 253-270. [9751] 7. Damman, A. W. H. 1977. Geographical changes in the vegetation pattern of raised bogs in the Bay of Fundy region of Maine and New Brunswick. Vegetatio. 35(3): 137-151. [10158] 8. Damman, Antoni W. H.; French, Thomas W. 1987. The ecology of peat bogs of the glaciated northeastern United States: a community profile. Biological Report 85(7.16). Washington, DC: U.S. Department of the Interior, Fish and Wildlife Service, Research and Development, National Wetlands Research Center. 100 p. [9238] 9. Dansereau, Pierre. 1959. The principal plant associations of the Saint Lawrence Valley. No. 75. Montreal, Canada: Contrib. Inst. Bot. Univ. Montreal. 147 p. [8925] 10. Dansereau, Pierre; Segadas-Vianna, Fernando. 1952. Ecological study of the peat bogs of eastern North America. Canadian Journal of Botany. 30(5): 490-520. [8869] 11. Ehrenfeld, Joan G. 1986. Wetlands of the New Jersey Pine Barrens: the role of species composition in community function. American Midland Naturalist. 115(2): 301-313. [8650] 12. Eyre, F. H., ed. 1980. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters. 148 p. [905] 13. Famous, Norman C.; Spencer, M. 1989. Revegetation patterns in mined peatlands in central and eastern North America studied. Restoration and Management Notes. 7(2): 95-96. [10171] 14. Flinn, Marguerite Adele. 1980. Heat penetration and early postfire regeneration of some understory species in the Acadian forest. Halifax, NB: University of New Brunswick. 87 p. Thesis. [9876] 15. Flinn, Marguerite A.; Pringle, Joan K. 1983. Heat tolerance of rhizomes of several understory species. Canadian Journal of Botany. 61: 452-457. [8444] 16. Flinn, Marguerite A.; Wein, Ross W. 1977. Depth of underground plant organs and theoretical survival during fire. Canadian Journal of Botany. 55: 2550-2554. [6362] 17. Flinn, Marguerite A.; Wein, Ross W. 1988. Regrowth of forest understory species following seasonal burning. Canadian Journal of Botany. 66: 150-155. [3014] 18. Foster, David R. 1985. Vegetation development following fire in Picea mariana (black spruce) - Pleurozium forests of south-eastern Labrador, Canada. Journal of Ecology. 73: 517-534. [7222] 19. Garrison, George A.; Bjugstad, Ardell J.; Duncan, Don A.; [and others]. 1977. Vegetation and environmental features of forest and range ecosystems. Agric. Handb. 475. Washington, DC: U.S. Department of Agriculture, Forest Service. 68 p. [998] 20. Gottschalk, Kurt W. 1988. Gypsy moth and regenerating Appalachian hardwood stands. In: Smith, H. Clay; Perkey, Arlyn W.; Kidd, William E., Jr., eds. Guidelines for regenerating Appalachian hardwood stands: Workshop proceedings; 1988 May 24-26; Morgantown, WV. SAF Publ. 88-03. Morgantown, WV: West Virginia University Books: 241-254. [13950] 21. Hall, I. V. 1959. Plant populations in blueberry stands developed from abandoned hayfields and woodlots. Ecology. 40(4): 742-743. [9108] 22. Kartesz, John T.; Kartesz, Rosemarie. 1980. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. Volume II: The biota of North America. Chapel Hill, NC: The University of North Carolina Press; in confederation with Anne H. Lindsey and C. Richie Bell, North Carolina Botanical Garden. 500 p. [6954] 23. Keppie, Daniel M.; Towers, Julie. 1990. Using phenology to predict commencement of nesting of female spruce grouse (Dendragapus canadensis). American Midland Naturalist. 124(1): 164-170. [12590] 24. Kingsbury, John M. 1964. Poisonous plants of the United States and Canada. Englewood Cliffs, NJ: Prentice-Hall, Inc. 626 p. [122] 25. Kuchler, A. W. 1964. Manual to accompany the map of potential vegetation of the conterminous United States. Special Publication No. 36. New York: American Geographical Society. 77 p. [1384] 26. Little, S. 1964. Fire ecology and forest management in the New Jersey pine region. In: Proceedings, 3rd annual Tall Timbers fire ecology conference; 1964 April 9-10; Tallahassee, FL. No. 3. Tallahassee, FL: Tall Timbers Research Station: 35-59. [5893] 27. Lyon, L. Jack; Stickney, Peter F. 1976. Early vegetal succession following large northern Rocky Mountain wildfires. In: Proceedings, Tall Timbers fire ecology conference and Intermountain Fire Research Council fire and land management symposium; 1974 October 8-10; Missoula, MT. No. 14. Tallahassee, FL: Tall Timbers Research Station: 355-373. [1496] 28. MacLean, David A.; Wein, Ross W. 1977. Changes in understory vegetation with increasing stand age in New Brunswick forests: species composition, cover, biomass, and nutrients. Canadian Journal of Botany. 55: 2818-2831. [10106] 29. Mallik, A. U. 1991. Cutting, burning, and mulching to control Kalmia: results of a greenhouse experiment. Canadian Journal of Forest Research. 21: 417-420. [14426] 30. Martin, J. Lynton. 1955. Observations on the origin and early development of a plant community following a forest fire. Forestry Chronicle. 31: 154-161. [11363] 31. Martin, J. Lynton. 1956. An ecological survey of burned-over forest land in southwestern Nova Scotia. Forestry Chronicle. 32: 313-336. [8932] 32. Niering, William A.; Goodwin, Richard H. 1974. Creation of relatively stable shrublands with herbicides: arresting "succession" on rights-of-way and pastureland. Ecology. 55: 784-795. [8744] 33. Raunkiaer, C. 1934. The life forms of plants and statistical plant geography. Oxford: Clarendon Press. 632 p. [2843] 34. Roland, A. E.; Smith, E. C. 1969. The flora of Nova Scotia. Halifax, NS: Nova Scotia Museum. 746 p. [13158] 35. Smith, David William. 1966. Studies in the taxonomy and ecology of blueberries (Vaccinium, subgenus Cyanococcus) in Ontario. Toronto, ON: University of Toronto. 276 p. Dissertation. [10872] 36. Soper, James H.; Heimburger, Margaret L. 1982. Shrubs of Ontario. Life Sciences Misc. Publ. Toronto, ON: Royal Ontario Museum. 495 p. [12907] 37. Strang, R. M. 1971. The ecology of the rocky heathlands of western Nova Scotia. In: Proceedings, annual Tall Timbers fire ecology conference; 1970 August 20-21; Fredericton, NB. No. 10. Tallahassee, FL: Tall Timbers Research Station: 287-292. [5466] 38. Telfer, E. S. 1972. Understory biomass in five forest types in southwestern Nova Scotia. Canadian Journal of Botany. 50: 1263-1267. [13933] 39. Thompson, I. D.; Mallik, A. U. 1989. Moose browsing and allelopathic effects of Kalmia angustifolia on balsam fir regeneration in central Newfoundland. Canadian Journal of Forest Research. 19(4): 524-526. [13238] 40. U.S. Department of Agriculture, Natural Resources Conservation Service. 2018. PLANTS Database, [Online]. U.S. Department of Agriculture, Natural Resources Conservation Service (Producer). Available: https://plants.usda.gov/. [34262] 41. Van Dersal, William R. 1938. Native woody plants of the United States, their erosion-control and wildlife values. Washington, DC: U.S. Department of Agriculture. 362 p. [4240] 42. Viereck, Leslie A.; Johnston, William F. 1990. Picea mariana (Mill.) B.S.P. black spruce. 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: 227-237. [13386] 43. Hall, Ivan V.; Jackson, Lloyd P.; Everett, C. Fred. 1973. The biology of Canadian weeds. 1. Kalmia angustifolia L. Canadian Journal of Plant Science. 53: 865-873. [14592] 44. Stickney, Peter F. 1989. Seral origin of species originating in northern Rocky Mountain forests. Unpublished draft on file at: U.S. Department of Agriculture, Forest Service, Intermountain Research Station, Fire Sciences Laboratory, Missoula, MT; RWU 4403 files. 7 p. [20090]

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