Apocynum cannabinum



INTRODUCTORY


 

Photo by Steve Dewey, Utah State University, www.forestryimages.org

AUTHORSHIP AND CITATION:
Reeves, Sonja L. 2006. Apocynum cannabinum. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [].

FEIS ABBREVIATION:
APOCAN

SYNONYMS:
A. hypericifolium Ait.
A. pubescens Mitchell ex R. Br.
A. sibiricum Jacq.
A. suksdorfii Greene [72]

NRCS PLANT CODE [141]:
APCA

COMMON NAMES:
Indianhemp
common dogbane
dogbane
hemp dogbane
prairie dogbane

TAXONOMY:
The scientific name of Indianhemp is Apocynum cannabinum L. (Apocynaceae) [72]. Hybridization is a common occurrence in this genus [3]. Apocynum floribundum Greene is a hybrid of spreading dogbane (A. androsaemifolium) and Indianhemp [3,70]. When information specific to Indianhemp is not available, information on the genus Apocynum is given.

LIFE FORM:
Forb

FEDERAL LEGAL STATUS:
None

OTHER STATUS:
None

DISTRIBUTION AND OCCURRENCE

SPECIES: Apocynum cannabinum
GENERAL DISTRIBUTION:
Indianhemp occurs in North America [156]. It is found throughout all of the lower 48 United States and most of Canada, including Newfoundland. Historic populations in Maryland have been extirpated [72]. Plants Database provides a distributional map of Indian hemp.

ECOSYSTEMS [54]:
FRES10 White-red-jack pine
FRES11 Spruce-fir
FRES12 Longleaf-slash pine
FRES14 Oak-pine
FRES15 Oak-hickory
FRES16 Oak-gum-cypress
FRES17 Elm-ash-cottonwood
FRES18 Maple-beech-birch
FRES19 Aspen-birch
FRES20 Douglas-fir
FRES21 Ponderosa pine
FRES28 Western hardwoods
FRES29 Sagebrush
FRES32 Texas savanna
FRES33 Southwestern shrubsteppe
FRES36 Mountain grasslands
FRES38 Plains grasslands
FRES39 Prairie

STATES/PROVINCES: (key to state/province abbreviations)
UNITED STATES
AL AZ AR CA CO CT DE FL GA ID
IL IN IA KS KY LA ME MD MA MI
MN MS MO MT NE NV NH NJ NM NY
NC ND OH OK OR PA RI SC SD TN
TX UT VT VA WA WV WI WY DC PR
VI

CANADA
AB BC MB NB NF NT NS ON PQ SK

BLM PHYSIOGRAPHIC REGIONS [16]:
1 Northern Pacific Border
2 Cascade Mountains
3 Southern Pacific Border
4 Sierra Mountains
5 Columbia Plateau
6 Upper Basin and Range
7 Lower Basin and Range
8 Northern Rocky Mountains
9 Middle Rocky Mountains
10 Wyoming Basin
11 Southern Rocky Mountains
12 Colorado Plateau
13 Rocky Mountain Piedmont
14 Great Plains
15 Black Hills Uplift
16 Upper Missouri Basin and Broken Lands

KUCHLER [79] PLANT ASSOCIATIONS:
K011 Western ponderosa forest
K012 Douglas-fir forest
K026 Oregon oakwoods
K038 Great Basin sagebrush
K053 Grama-galleta steppe
K054 Grama-tobosa prairie
K056 Wheatgrass-needlegrass shrubsteppe
K063 Foothills prairie
K064 Grama-needlegrass-wheatgrass
K066 Wheatgrass-needlegrass
K067 Wheatgrass-bluestem-needlegrass
K068 Wheatgrass-grama-buffalo grass
K069 Bluestem-grama prairie
K074 Bluestem prairie
K081 Oak savanna
K082 Mosaic of K074 and K100
K084 Cross Timbers
K093 Great Lakes spruce-fir forest
K095 Great Lakes pine forest
K096 Northeastern spruce-fir forest
K098 Northern floodplain forest
K100 Oak-hickory forest
K101 Elm-ash forest
K104 Appalachian oak forest
K111 Oak-hickory-pine
K112 Southern mixed forest

SAF COVER TYPES [49]:
1 Jack pine
16 Aspen
17 Pin cherry
18 Paper birch
20 White pine-northern red oak-red maple
37 Northern white-cedar
39 Black ash-American elm-red maple
40 Post oak-blackjack oak
46 Eastern redcedar
61 River birch-sycamore
63 Cottonwood
70 Longleaf pine
71 Longleaf pine-scrub oak
75 Shortleaf pine
76 Shortleaf pine-oak
78 Virginia pine-oak
79 Virginia pine
83 Longleaf pine-slash pine
95 Black willow
107 White spruce
108 Red maple
210 Interior Douglas-fir
217 Aspen
222 Black cottonwood-willow
233 Oregon white oak
235 Cottonwood-willow
237 Interior ponderosa pine
252 Paper birch

SRM (RANGELAND) COVER TYPES [127]:
101 Bluebunch wheatgrass
401 Basin big sagebrush
411 Aspen woodland
601 Bluestem prairie
602 Bluestem-prairie sandreed
604 Bluestem-grama prairie
606 Wheatgrass-bluestem-needlegrass
607 Wheatgrass-needlegrass
608 Wheatgrass-grama-needlegrass
609 Wheatgrass-grama
610 Wheatgrass
731 Cross timbers-Oklahoma

HABITAT TYPES AND PLANT COMMUNITIES:
Indianhemp is not an indicator or dominant species in vegetation typings. It is considered a characteristic (secondary) plant species in the wet-meadow vegetation of the Prairie Potholes in North Dakota [132]. In Virginia, Indianhemp is "particularly characteristic" of the Rocky Bars and Shores communities of the palustrine-alluvial floodplain communities [52].

Other communities where Indianhemp is known to occur:


BOTANICAL AND ECOLOGICAL CHARACTERISTICS

SPECIES: Apocynum cannabinum

 

  James H. Miller, USDA Forest Service, www.forestryimages.com
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 [17,31,38,50,57,91,112,125,134,155,158].

Indianhemp is a native, perennial, broadleaf herb. In some cases, it is considered a weed [15,77,104,119]. It has an erect to ascending growth habit and reaches heights of 2 to 6 feet (0.6-1.8 m) from a spreading root stalk [15,28,77,119,156] Branching is opposite or sub-opposite [156]. The leaves are opposite, ovate to lanceololate, entire, and glabrous to sparingly pubescent beneath [5,15,28,119,156]. The flowers consist of 5 petals occurring in terminal clusters from the leaf axils [15,119]. The inflorescence of Indianhemp is a trichasial cyme. The lateral cymes of the trichasium can continue growing vegetatively to form a complete stem with their own terminal trichasiums [156]. The fruits are slender, pencil-like, hanging pods that are 4 to 8 inches (10-20 cm) long and occur in pairs. Seeds are flat, thin, and tufted with soft hairs [15,77,119]. Indianhemp leaves, stems, and roots all contain milky juice [14,15,28,119].

Indianhemp has 2 underground organs: the 1st are thick, branched, horizontal rhizomes that produce new aerial shoots at variable depths. The 2nd are slender, well-branched, vertical, absorbing roots [99]. These large roots/rhizome systems have been found as deep as 13 feet (4 m) below the soil surface and may extend up to 20 feet (6 m) in radial spread [76,104].

RAUNKIAER [114] LIFE FORM:
Hemicryptophyte
Geophyte

REGENERATION PROCESSES:
Indianhemp regenerates by seed and vegetative means. Regeneration is largely by vegetative means from rhizomes or from root crown buds located at the woody base of stems [15,55,104,119,147].

Pollination: Indianhemp is visited by 19 species of bees and wasps, 17 species of flies, 2 species of butterflies and/or moths, 1 species of beetle, and 2 species of bugs and/or aphids. However, it appears that these visits do not succeed in pollination. Successful transfer of pollen seems to occur only when the insect is trapped in the flower and struggles to escape, in turn collecting pollen [156]. Bees, butterflies, and flies were observed as nectar feeders on Apocynum flowers. Pollen was not observed on any of these insects after visiting the flowers [70]. Indianhemp does not self pollinate [70,156].

Breeding system: Apocynum flowers depend largely on cross-pollination for sexual reproduction [156]. Cross-pollination is frequent in the genus [3].

Seed production: Indianhemp can produce numerous seeds [69,113]. A study by Shultz and Burnside [122] in Nebraska reveals that the number of seeds produced by an individual plant is dependent on the amount of competition for water, light, and nutrients. Grown without any competition Indianhemp produced up to 150 pods with 81 seeds per pod. When grown with soybeans (Glycine max), Indianhemp only produced 2 pods/plant on average [122]. Seed production in disturbed areas was around 600/plant [109].

Seed dispersal: Indianhemp seeds are dispersed by wind and gravity [96,97,139]. The small seeds are specialized for dispersal over long distances. They have a very large, fine coma (a tuft of hairs on the seed) that facilitates wind dispersal [92,108,109,139,147].

Seed banking: Seed dormancy of Indianhemp is unclear, though viability of Indianhemp seed declines rapidly in soil [23,113]. Burial studies indicated that the seeds are not long-lived and that the seeds do not persist after 1 year in the soil [12,24]. In Pennsylvania Indianhemp has been found in the aboveground vegetation and not in the seed bank [84]. Conversely, Indianhemp emerged from the seed bank of a Delaware River freshwater tidal wetland [86]. Further research is needed on the seed dormancy of Indianhemp.

Germination: Germination ability of Indianhemp seed depends on burial depth and seed age. A long-term study done by Burnside and others [23] tested the viability of seeds buried at a depth of 8 inches (20 cm). At the 1st study site there was 74% seed germination at year 0, 22% seed germination after burial of 1 year, and 0% in years after that. At the 2nd site germination rates were 74% at year 0, 52% after year 1, 13% in year 2, and 1% in year 4 and 6 [23]. In another laboratory study the greatest germination occurred when seeds were buried at 0.4 inch (1 cm), and germination declined greatly at greater depths [116].

A study by Everetts and Burnside [48] comparing temperature and germination of Indianhemp seed revealed that successful germination occurred between 59 F to 95 F (15-35 C). The highest germination rate occurred at 95 F (35 C).

Stratification inhibited Indianhemp seed germination in a greenhouse study done by Greene and Curtis [59]. After 3 months of stratification 0% of the seeds germinated, while 10% of unstratified seed germinated.

Seedling establishment/growth: A study by Everetts and Burnside [48] comparing Indianhemp seedling development and temperature found seedling establishment occurred at 59 F to 95 F (15-35 C). Indianhemp could not establish seedlings at or below 50 F (10 C) or at or above 100 F (40 C) [48]. Best establishment occurs on moist sites [108].

Asexual regeneration: Apocynum species spread by cloning [70]. Indianhemp reproduces by rhizomes or sprouting from the root crown [15]. Aerial shoots arise from adventitious rhizome buds. Rhizomes spread extensively, forming new plants at "considerable" distances [76,99]. Seedlings are capable of sprouting within 10 to 41 days of emergence [15,119].

SITE CHARACTERISTICS:
Indianhemp can grow in diverse environments [113]. It prefers damp locations along streams and ditches and in marshes, though it can be found growing less abundantly in drier locations such as thickets, open woods, and open ground [35,70].

Indianhemp is seldom found on soils low in fertility. It grows best on fertile, medium- to heavy-textured soils [116,160].

The following table describes site characteristics for Indianhemp throughout its distribution.

State/Region/Province Site Characteristics
Arizona Streambeds in woodlands and riparian woodlands between 3,000 to 7,500 feet (910-2,300 m) [18,74]
California Damp/moist places near streams, springs, and ditches below 7,000 feet (2,100 m), sometimes in deserts or a weed in orchards [28,63,101,102]
Colorado Roadside ditches and floodplains between 3,500 and 7,500 feet (1,100-2,300 m) [61,145,146]
Illinois Prairies, fields, abandoned fields and rocky woods [89,98]
Kansas Prairies, streambanks, roadsides, and "waste grounds" [11]
Minnesota Pipestone National Monument: rock outcrops, woodlands, and tallgrass prairies [13]
Montana Hills, slopes, moist, shady areas, and disturbed areas [17,42]; sometimes found in wetlands, but also occurs in drier sites [115]
     west-central Montana Along rivers below high water marks, on islands, and low banks. Often in half shade beneath tree canopies, also on gravelly, vernally moist to wet places, and on disturbed sites. Dry to moist valleys [81,82]
Nevada Gravelly slopes, damp ditch banks or canyon bottoms from 2,800 to 6,500 feet (850-2,000 m) [73]
Nebraska Occurs in patches in field crops and may occur as a dense infestation throughout the field [160]; ravines and wet meadows [131]
New Mexico Moist, open, or "waste ground" between 3,500 and 7,500 feet (1,100-2,300 m) [91]
New York

Wet meadows and margins of bogs [126]. Rarely found on Fire Island (off Long Island, New York) on dry, open sandflats and sandy dredged material [44]

North Carolina Disturbed areas, old fields, and roadsides [94]
Ohio Moist to mesic fields and thickets, pond and stream margins, moist to mesic woodland openings and borders, railways, roadsides, and other "waste places" [5]
Oregon "Wastelands" and seldom cultivated areas, especially in orchards [139]
South Dakota - Black Hills Hills, streambanks, and railroad embankments [41,93]
Texas Open or disturbed, often moist ground. Sandy, gravelly, or eroding clayey soils [38]
Utah Roadsides, fields, streambanks, and disturbed sites mainly in riparian communities between 3,200 to 7,700 feet (970-2,350 m). "Poorly kept" agricultural lands [57,152]
Virginia Low woods [151]
Wyoming Hills, slopes, and disturbed areas [43]
Great Plains Prairies, river floodplains, terraces, open or woodland waterways or lakeshores, disturbed roadsides or fields, ditches, and sparsely wooded slopes [58,70]
Intermountain west Moist to moderately moist, disturbed areas along roadsides and ditch-banks between 1,600 to 7,200 feet (500-2,200 m) [34]
Northern Great Plains Borders of marshes, lakes, streams and other moist to wet places, often in disturbed areas [83]
Ozark Mountains Glades, prairies, open woods, and "waste ground" [33]
Pacific Northwest A "serious" weed on "wasteland" areas that are infrequently plowed, occasionally a problem in orchards [64,65]
western U.S. Grows on plains and foothills at elevations up to 7000 feet (2,100 m). Commonly found on gravelly or sandy fields, in meadows, and along creekbeds, irrigation ditches, and fence lines in cultivated pastures [69,140]
British Columbia Collected in draws and exposed banks [1]
Nova Scotia Gravelly beaches and cobbley or sandy stream banks [117]
Baja California Streams and ditches, meadows, and hillsides [154]

SUCCESSIONAL STATUS:
Indianhemp is most often referred to as an early successional species. It colonizes disturbed sites, abandoned agricultural fields, and prairie pot hole wetlands [75,100,108]. On restored prairies in Arkansas, Indianhemp established during the 2nd year after disturbance, declined during the 3rd year, and generally disappeared or was greatly diminished by the 4th growing season, when it was overtopped by other species [36].

Indianhemp is occasional in older (20 to 30 years) jack pine (Pinus banksiana) and mixed-hardwood stands in New Brunswick [88].

SEASONAL DEVELOPMENT:
Seasonal development of Indianhemp begins with emergence in late spring or early summer [69,140]. Established plants initiate growth in the spring from root crown and rhizome buds [116,160]. The lateral cymes continue to add vegetative tissue, prolonging the productive potential of the plant. In this manner Indianhemp may continue bloom and vegetative growth from spring until late in the autumn, giving it a distinct advantage over the much shorter periods of growth of the other Apocynum species [156].

The seasonal nonstructural carbohydrate levels of Indianhemp decline with vegetative growth in the spring, reach seasonal lows during flowering, and then increase until fall dormancy [14].

The following table details the different flowering periods of Indianhemp throughout its distribution.

State/Region/Province Anthesis Period
Arizona May to August [74]
California June to August [101,102]
Illinois May to August [89,98]
Kansas Mid-May to mid-August [11]
Nebraska June to August [131]
Nevada June to August [73]
New Mexico May to September [91]
North Dakota June to July [26]
Ohio June to August [5]
Texas April to July [38,46]
Utah - Uinta Basin June to August [57]
Great Plains May to September [58,135]
Intermountain west May to August [34]
Northern Great Plains June to August, fruiting August to October [83]
Pacific Northwest June to September [64,65]
Nova Scotia July to August [117]
Baja California June to July [154]

Phenological data for Indianhemp growing along a tall fescue (Festuca arundinacea) waterway at Lincoln, Nebraska is given below [122].

Growth Stage 1977 1978
Emergence April 18 April 29
Bud May 20 June 2
Early flower May 26 June 13
Full bloom June 4 June 21
Pod initiation June 17 not produced

FIRE ECOLOGY

SPECIES: Apocynum cannabinum
FIRE ECOLOGY OR ADAPTATIONS:
Fire adaptations: Indianhemp has an extensive, deep root and rhizome system, and sprouts from the root crown and rhizomes after top-kill by fire. For example, populations near Ottawa, Ontario, sprouted from both rhizomes and root crowns following severe fire [27]. Indianhemp also reproduces from wind-blown seed [96,97], so postfire establishment from seed is possible. The ability of Indianhemp to colonize disturbed areas may give it an advantage on burned soils.

Fire regimes: The extensive distribution of Indianhemp places it in a wide range of fire regimes. Plains and mountain grasslands where Indianhemp occurs have short fire-return intervals and could burn in any year if fuels are cured [20]. Indianhemp is found in communities with mixed-severity and understory fire regimes as described by Brown and Smith [20]. The following table provides fire return intervals for plant communities and ecosystems where Indianhemp occurs. For further information, see the FEIS review of the dominant species listed below.

Community or Ecosystem Dominant Species Fire Return Interval Range (years)
maple-beech Acer-Fagus spp. 684-1,385 [30,144]
maple-beech-birch Acer-Fagus-Betula spp. >1,000 [144]
Nebraska sandhills prairie Andropogon gerardii var. paucipilus-Schizachyrium scoparium <10
bluestem-Sacahuista prairie Andropogon littoralis-Spartina spartinae <10
sagebrush steppe Artemisia tridentata/Pseudoroegneria spicata 20-70 [106]
basin big sagebrush Artemisia tridentata var. tridentata 12-43 [120]
birch Betula spp. 80-230 [136]
plains grasslands Bouteloua spp. <35 [106,157]
blue grama-needle-and-thread grass-western wheatgrass Bouteloua gracilis-Hesperostipa comata-Pascopyrum smithii <35 [106,118,157]
blue grama-buffalo grass Bouteloua gracilis-Buchloe dactyloides <35 [106,157]
grama-galleta steppe Bouteloua gracilis-Pleuraphis jamesii <35 to <100 [106]
cheatgrass Bromus tectorum <10 [107,153]
black ash Fraxinus nigra <35 to 200 [144]
green ash Fraxinus pennsylvanica <35 to >300 [47,144]
wheatgrass plains grasslands Pascopyrum smithii <5-47+ [106,111,157]
Great Lakes spruce-fir Picea-Abies spp. 35 to >200
northeastern spruce-fir Picea-Abies spp. 35-200 [45]
jack pine Pinus banksiana <35 to 200 [30,45]
shortleaf pine Pinus echinata 2-15
shortleaf pine-oak Pinus echinata-Quercus spp. <10 [144]
longleaf-slash pine Pinus palustris-P. elliottii 1-4 [103,144]
longleaf pine-scrub oak Pinus palustris-Quercus spp. 6-10 [144]
interior ponderosa pine* Pinus ponderosa var. scopulorum 2-30 [7,10,85]
red pine (Great Lakes region) Pinus resinosa 3-18 (x=3-10) [29,53]
eastern white pine Pinus strobus 35-200 [136,144]
Virginia pine Pinus virginiana 10 to <35
Virginia pine-oak Pinus virginiana-Quercus spp. 10 to <35
sycamore-sweetgum-American elm Platanus occidentalis-Liquidambar styraciflua-Ulmus americana <35 to 200 [144]
eastern cottonwood Populus deltoides <35 to 200 [106]
quaking aspen-paper birch Populus tremuloides-Betula papyrifera 35-200 [45,144]
quaking aspen (west of the Great Plains) Populus tremuloides 7-120 [7,60,95]
mountain grasslands Pseudoroegneria spicata 3-40 (x=10) [6,7]
Rocky Mountain Douglas-fir* Pseudotsuga menziesii var. glauca 25-100 [7,8,9]
oak-hickory Quercus-Carya spp. <35 [144]
Oregon white oak Quercus garryana <35 [7]
oak savanna Quercus macrocarpa/Andropogon gerardii-Schizachyrium scoparium 2-14 [106,144]
post oak-blackjack oak Quercus stellata-Q. marilandica <10 [144]
little bluestem-grama prairie Schizachyrium scoparium-Bouteloua spp. <35 [106]
*fire return interval varies widely; trends in variation are noted in the species review

POSTFIRE REGENERATION STRATEGY [133]:
Rhizomatous herb, rhizome in soil
Geophyte, growing points deep in soil
Secondary colonizer (on-site or off-site seed sources)

FIRE EFFECTS

SPECIES: Apocynum cannabinum
IMMEDIATE FIRE EFFECT ON PLANT:
Fire likely top-kills Indianhemp. It is probably resistant to fire-induced mortality because of its deep root and rhizome system.

DISCUSSION AND QUALIFICATION OF FIRE EFFECT:
The development of new Indianhemp plants 100 days following severe fire in Ontario, on a site previously dominated by white spruce and quaking aspen, resulted from rhizome and root crown sprouts [27].

PLANT RESPONSE TO FIRE:
There are conflicting results as to how Indianhemp responds to fire. Johnson and Knapp [71] stated that populations of Indianhemp increased with increased fire frequency on tallgrass prairie in Kansas [71]. However, Tester [137] found a nonsignificant negative effect of burn frequency on Indianhemp in an oak savanna of east-central Minnesota [137].

Indianhemp was found on all 5 burned study plots 100 days after fire in a white spruce-quaking aspen site in Ontario [27]. Indianhemp also produced new spring growth within days following a prescribed burn in a tallgrass prairie in Kansas [71].

Prescribed burns were implemented in consecutive years in an oak savanna in east-central Illinois. The 1st fire resulted in a "hot, intense" fire, and the fire the following year was not as hot or intense. Indianhemp increased on burned sites but only in the 2nd postfire year [67]. It increased in percent cover on both control and burn plots studied after a prescribed fire on a mid-elevation wetland in southeastern Arizona [51].

Conversely, the findings of Bowles and others [19] indicate that Indianhemp populations did not survive after 8 dormant-season prescribed burns on graminoid fens in Cook County, Illinois. Indianhemp plants were recorded on the study plots before burning, but were not present after 5 years [19]. On study plots dominated by post oak, winged elm (Ulmus alata), and white ash (Fraxinus americana) in southern Illinois, Indianhemp was observed during prefire sampling and not found in postfire months 5 or 6 (burns characterized as "moderate, at best") [62]. In a sedge-beaked spikerush-Kentucky bluegrass (Carex spp.-Eleocharis rostellata-Poa pratensis) wetland near Tucson, Arizona, Indianhemp density increased more on control plots than burned plots. Indianhemp increased on high-frequency repeat spring burns (every 2-3 years), medium-frequency repeat spring burns (every 5-7 years), and unburned control plots [51]. However, analyses of variance failed to demonstrate a significant (p=0.70) effect of burning on Indianhemp cover.

DISCUSSION AND QUALIFICATION OF PLANT RESPONSE:
No additional information is available on this topic.

FIRE MANAGEMENT CONSIDERATIONS:
The current body of research provides no clear direction for using fire as a management tool for Indianhemp populations. The results of studies done to date, 2006, are conflicting. Further research is needed on the fire ecology of Indianhemp.

MANAGEMENT CONSIDERATIONS

SPECIES: Apocynum cannabinum
IMPORTANCE TO LIVESTOCK AND WILDLIFE:
Indianhemp is poisonous to all livestock, although domestic sheep are affected more than other animals [15,33,35,69,110,119,123,129,140]. However, actual cases of livestock poisoning from Indianhemp are rare [15,35]. Traces of Indianhemp were found in rumen samples of pronghorn and white-tailed deer in Montana, but no animals were observed eating it [2,32].

Indianhemp is a primary host for 2 species of leaf beetle [40]. It is also a host plant for Chrysochus auratus (a root beetle) in Iowa. Chrysochus auratus mating and ovipositing occur on Indianhemp throughout the summer. Once hatched, the larvae drop to the ground and tunnel to the roots of the host plants, where they feed and overwinter [130].

Butterfly gardeners grow Indianhemp because it is a valuable native nectar plant [68].

Palatability/nutritional value: Indianhemp is unpalatable at all seasons, even to livestock that are virtually starving [46]. Animals usually avoid Indianhemp because of the bitter, sticky, milky-white juice; however, domestic sheep may eat large quantities if other forage is scarce [69,140].

All parts of Indianhemp, fresh or dried, are poisonous because of the toxic glycoside it contains [33,35,69,123,140]. The levels of the glycoside, cymarin, in Indianhemp are disputed. Knight [77] claims the levels of cymarin are low and Majak [90] states that there are high concentrations. Death from Indianhemp poisoning may occur 6 to 12 hours after animals eat the plant. A lethal dose for domestic sheep is about 0.5 to 1 ounce/100 pounds of body weight. A lethal dose for cattle and horses is about 0.5 to 0.75 ounce/100 pounds of body weight [69,140].

Cover value: Cover of Indianhemp for wildlife has been rated as follows [39]:

  UT MT
elk poor ----
mule deer poor ----
white-tailed deer ---- fair
pronghorn poor ----
small mammals fair ----
small nongame birds fair ----
upland game birds poor ----
waterfowl poor ----

VALUE FOR REHABILITATION OF DISTURBED SITES:
There is value in using Indianhemp for the rehabilitation of disturbed sites. It grows very well in disturbed areas. It is, for example, common on American badger-disturbed sites [108,109]. It is also recognized as a worthwhile native landscaping plant because it spreads rapidly by vegetative means and can help suppress weeds [37].

OTHER USES:
Indianhemp is known for its importance to early Native Americans. The strong, fibrous root and stem fibers were used to make fish nets, rope, thread, baskets, cloth, and bags [1,4,15,28,35,78,105,121,128,138,156].

Indianhemp is known to have many medicinal purposes. The glycoside, cymarin, was used as a cardiac stimulant, a diuretic, a diaphoretic, a febrifuge, a rheumatism remedy, and a treatment for gall stones [35,69,78,128,140]. The dried milky fluid in the stems can be used as a chewing gum substitute [78].

The fragrant flowers attract honeybees for nectar, making a "superior," almost colorless honey [33].

There may be potential for using Indianhemp as a hydrocarbon-producing crop as an energy alternative [21].

OTHER MANAGEMENT CONSIDERATIONS:
Indianhemp is considered a serious weed problem in agricultural fields in the Midwest and can cause decreases in yield [14,22,76,104,116,147,148,149,150,160]. Infestations tend to occur in agricultural crops where no-tillage systems have been implemented, which allow for Indianhemp's rhizome and root system to become well established [56,147,148,149]. Reductions in yield are reportedly due to allelopathic influences of Indianhemp [122,159]. Indianhemp is also considered a weed species in nurseries, plantations where Christmas trees are grown, and in orchards [64,65,80].

Indianhemp increases on grazed pastures in South Dakota [87].

Control: Many management strategies have been used to try to control Indianhemp, with different levels of success. Complete control is difficult due to Indianhemp's persistent and extensive root and rhizome system [104].

Integrated management: A successful management program to control Indianhemp likely includes a combination of cultural, mechanical (tillage including the usage of plows, disks, or cultivators), and chemical methods [119] as well as an appropriate schedule for implementing these methods. There is widespread agreement that timing of control methods is critical and can make weed management very difficult [56,104,147,149]. Fall herbicide treatments have provided better control than spring treatments. The spring treatments can effectively control Indianhemp, but the timing often occurs when the most damage can be done to other herbs [14,116,160]. Becker [15] states that herbicide application timing should coincide with late bud to early flower set, or beyond. Mechanical methods such as mowing, cultivation, or tilling practices should be implemented at mid- to full-flower, before root carbohydrate levels begin, to recover to maximize carbohydrate depletion [14].

Physical/mechanical: Mechanical control has been shown to decrease and increase infestations. Numerous Indianhemp sprouts occurred on study plots that had the soil scraped off. The scraping and deep plowing destroyed most of the perennating tissues except for the some deeply buried rhizomes. The following year Indianhemp continued to spread and increase in height. A steady decrease was observed in the following years, until it was absent or of little importance [75]. Buhler and others [22] state that Indianhemp can be controlled by tillage systems. Tillage can reduce infestations if done frequently (every 2 to 3 weeks) enough to deplete underground root reserves [119]. Increases in infestations where tillage practices are used have been attributed to tillage equipment moving parts of the root systems to new areas and by breaking dormancy of underground buds, resulting in new shoot growth [122,160].

Chemical control has also had mixed success. The seedlings are "easily controlled" by most soil-applied herbicides including 2, 4-D and glyphosate. Once seedlings become established, control becomes much more difficult [15]. A broad range of herbicides was reported to be effective (80% to ≥92%) on Indianhemp seedlings in a greenhouse study in Delaware [142]. Depending on the herbicide, applications made during the vegetative stage of growth provide a shorter-term control than applications made during the early reproductive stage. Applying herbicides during the early reproductive stage provides the longer-term control but can be harmful to other herbs [104]. Applications of the "traditionally safe" herbicides sulfometuron methyl and imazapyr were used on Indianhemp in eastern white pine plantations were unsuccessful [80]. Glenn and Anderson [56] report good Indianhemp control with herbicide applications of 1 or more of the following: 2, 4-D, dicamba, nicosulfuron, and triclopyr; however, regrowth from the root crown occurred occasionally. Herbicide treatments reduce the vigor of Indianhemp plants but often do not kill them [160].

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