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Other communities where Indianhemp is known to occur:
Freshwater tidal marsh of the Merrimack River, Massachusetts in the high tide zone [25]
Weeping alkali grass (Puccinellia distans) association and seeps in canyons (vertical, loose, sandy soils) in Tsegi Canyon, Arizona [66]
Cultivated and uncultivated field crops [64,65,69,89,98,104,140,160]
Natural (vs. restored) prairie wetlands in northwest Iowa [124]
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| James H. Miller, USDA Forest Service, www.forestryimages.com |
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: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 ºF to 95 ºF (15-35 ºC). The highest germination rate occurred at 95 ºF (35 ºC).
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 ºF to 95 ºF (15-35 ºC). Indianhemp could not establish seedlings at or below 50 ºF (10 ºC) or at or above 100 ºF (40 ºC) [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 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] |
Indianhemp is occasional in older (20 to 30 years) jack pine (Pinus banksiana) and mixed-hardwood stands in New Brunswick [88].
SEASONAL DEVELOPMENT: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 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. 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".
| 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] |
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: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 | ---- |
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 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].1. Alldritt-McDowell, Judith; Coupe, Ray. 1998. The ecology of the bunchgrass zone. QP #004216. Victoria, BC: Ministry of Forests, Research Branch. 5 p. [29235]
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