General: The Legume family (Fabaceae). Purple prairie clover is a native, warm season, herbaceous, perennial, leguminous forb. The plant has an erect type growth habit that typically grows to a height of
30 to 90 cm. It can be identified by its alternate, pinnately compound leaves and multiple stems which arise annually from a woody caudex. The inflorescence is a terminal spike (2-4 cm), numerous, many-flowered and cylindrical in shape. The flower petals which are rose-purple with projecting gold-orange anthers are small and simple compared to many pea shaped flowers of typical legumes. The calyx is densely villous. Flower petals are 6 mm long, 4 of the petals and the five stamens are joined near the calyx tip and the banner petal is separate. The first flowers to bloom are located at the bottom of the spike and the circle of flowers moves upward along the spike as new buds open and old flowers fade. Pollination is accomplished by a host of native insects ranging from bumblebees to beetles (Art, 1991). The fruit is a one seeded legume pod enclosed by the persistent calyx which is 2-2.5 mm long. The legume seed is yellowish-green to brown and is 1.5-2.0 mm long and punctuate. Purple prairie clover flowers the last of May to September in the central Great Plains. It flowers some what later (July-August) in the northern Great Plains. This plant is deep rooted with a 2.0 meter tap root. It also has three to seven lateral roots within the upper 30 cm of tap root which extend horizontally up to 45 cm before turning downward (Weaver, 1954).
Distribution: For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site. Purple prairie clover ranges from Indiana to Saskatchewan and Montana, south to Tennessee, Arkansas, Texas and New Mexico. It is also found in Alabama and has been introduced east into New York State.
Habitat: Purple prairie clover occurs in prairies, rocky open glades, along railroad tracks, and rocky or open woods.
violet prairie clover, red tassel flower, thimbleweed, and wanahcha (Lakota)
Range and Habitat in Illinois
Regularity: Regularly occurring
Regularity: Regularly occurring
States or Provinces
Regional Distribution in the Western United States
This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):
BLM PHYSIOGRAPHIC REGIONS :
8 Northern Rocky Mountains
9 Middle Rocky Mountains
10 Wyoming Basin
11 Southern Rocky Mountains
13 Rocky Mountain Piedmont
14 Great Plains
15 Black Hills Uplift
16 Upper Missouri Basin and Broken Lands
This species grows on prairies, plains, and hills
in soils ranging from clay loams to loamy sands. Found growing more vigorously on well drained sites and moderately alkaline calcareous soils. Thrives in 40 to 50 cm precipitation zones, but found in suitable sites in the 30 to 38 cm rainfall zones. Purple prairie clover is moderately drought tolerant, has fair fire tolerance in its dormant state, and fairly shade tolerant and medium in competitiveness. Local ecotypes are fairly winter hardy and plants have been found up to about 2,200 meters in elevation in the Rocky Mountains. Purple prairie clover is normally found growing in association with native warm-season grasses such as Sorghastrum nutans, Bouteloua curtipendula, Andropogon gerardii, Schizachyrium scoparium, and Panicum virgatum.
The following description provides general characteristics that may be relevant to fire ecology, and is not meant for identification. Keys for identification are available (e.g. [6,43,48,49,100,108,112]).
Purple prairie clover is a perennial forb, 8 to 35 inches (20-90 cm) tall, with a woody stem. The numerous leaves are 0.4-1.6 inches (1-4 cm) long, with 3 to 7 leaflets. The inflorescence is a 0.4- to 2.6-inch (1-7 cm) spike located at the ends of the branches. Branches are numerous, usually 3 per stem, but sometimes as many as 10 to 12. The mature purple prairie clover has a coarse, nonfibrous root system with a strong woody taproot that is 5.5 to 6.5 feet (1.7-2.0 m) deep. The taproot gives rise to several minutely branched lateral roots. The fruit is a 1- to-2-seeded pod enclosed in bracts [6,48,62,100,112].
Catalog Number: US 496689
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Original publication and alleged type specimen examined
Preparation: Pressed specimen
Collector(s): D. Griffiths
Year Collected: 1903
Locality: Raton Mts., near Colorado-New Mexico Line., New Mexico, United States, North America
- Holotype: Rydberg, P. A. 1920. N. Amer. Fl. 24: 131.
Range and Habitat in Illinois
Purple prairie clover grows on a variety of sites throughout the Great Plains including dry plains, prairies, hillsides, open woodlands, shaded ravines, sandhills, and roadsides. It occurs on mesic and xeric sites in mixed-grass and tallgrass prairies of the northern and central Great Plains and the shortgrass prairie of the southern Great Plains [24,49,80]. It is most common on marginal sites where soil is exposed and grasses have not formed dense stands . Mean annual precipitation for regions where purple prairie clover subsists ranges from 11 inches (280 mm) in southeast Alberta  to 32 inches (810 mm) in Kansas  and Oklahoma  to 53 inches (1,350 mm) in Mississippi .
Soils: Purple prairie clover can be found in most soil types throughout the Great Plains . In the northern Great Plains purple prairie clover is found in sandy to silty loams [17,19]. Some specific soil characteristics have been identified with purple prairie clover in the Nebraska Sandhill prairie region. Here purple prairie clover occurs most frequently in sandy soils that contain medium to coarse grains. It is thought that the coarse sands intercept precipitation with minimal runoff, allowing most of the moisture to reach far below the surface. Due to its taproot morphology, purple prairie clover is able to access moisture from deep in the soil profile and thus is able to persist in areas where other shallow-rooted species cannot . Soils in Minnesota where purple prairie clover is present were found to have pH values of 6.4 to 6.7 , with soil depths ranging from 6 to 24 inches (15-6.1 cm) .
Elevation: In eastern Colorado purple prairie clover occurs at elevations from 3,500 to 7,500 feet (1,067-2,286 m) .
Key Plant Community Associations
Purple prairie clover is an important component of Great Plains grassland
communities. It is considered "common" in most
grassland habitat types of the midwestern United States and southern Canada. Graminoids dominate these regions, comprising 80%
to 90% to the total plant population. Purple prairie clover and other forbs generally make up 10% or less
of total plant population in the Midwest . Purple prairie clover is found in tallgrass, shortgrass, or mixed-grass prairies.
Common associates in tallgrass prairies include little bluestem (Schizachyrium scoparium), big bluestem
(Andropogon gerardii), prairie Junegrass (Koeleria macrantha),
prairie dropseed (Sporobolus heterolepis), lead plant (Amorpha canescens),
and silky aster (Aster sericeus). Associates in mid-grass
prairie include silver bluestem (Bothriochloa saccharoides),
purple threeawn (Aristida purpurea), sideoats grama (Bouteloua curtipendula), and sand dropseed
(Sporobolus cryptandrus). Grass associates in shortgrass prairie include blue grama (Bouteloua gracilis),
hairy grama (B. hirsuta), and buffalo grass (Buchloe
dactyloides). Forb associates include wavyleaf thistle (Cirsium undulatum),
gayfeather (Liatris punctata), and scarlet globemallow (Sphaeralcea
coccinea). Forbs may be interspersed with several shrubs including American hazelnut (Corylus
americana), smooth sumac (Rhus glabra), creeping juniper (Juniperus
horizontalis) and/or trees including green ash (Fraxinus pennsylvanica),
eastern cottonwood (Populus deltoides), eastern redcedar (Juniperus
virginiana), white oak (Quercus alba), bur oak (Q. macrocarpa),
and shagbark hickory (Carya ovata). Woody associates are especially
common near riparian areas and on grassland/forest ecotones in the northern and
eastern fringes of purple prairie clover's distribution [7,8,17,18,19,32,62].
Purple prairie clover also occurs in Nebraska sandhill prairie , cedar
glade, limestone glade, dolomite glade , dry-mesic savanna, dry-mesic prairie, wet-mesic alluvial floodplain , quaking
tremuloides)-prairie ecotone , and mesic bur
oak (Quercus macrocarpa), black oak (Quercus velutina),
white oak (Quercus alba), and northern pin oak (Quercus
ellipsoidalis) savanna communities . In Illinois, it occurs in dolomite-hill
prairie and "barren" communities [2,19].
In northern Arizona's Grand Canyon National Park,
purple prairie clover is considered an "exotic species,"
and is found in riparian areas of the canyon .
Habitat: Rangeland Cover Types
This species is known to occur in association with the following Rangeland Cover Types (as classified by the Society for Range Management, SRM):
More info for the terms: cover, hardwood, vine
SRM (RANGELAND) COVER TYPES :
301 Bluebunch wheatgrass-blue grama
303 Bluebunch wheatgrass-western wheatgrass
304 Idaho fescue-bluebunch wheatgrass
305 Idaho fescue-Richardson needlegrass
309 Idaho fescue-western wheatgrass
310 Needle-and-thread-blue grama
311 Rough fescue-bluebunch wheatgrass
322 Curlleaf mountain-mahogany-bluebunch wheatgrass
323 Shrubby cinquefoil-rough fescue
505 Grama-tobosa shrub
601 Bluestem prairie
602 Bluestem-prairie sandreed
603 Prairie sandreed-needlegrass
604 Bluestem-grama prairie
605 Sandsage prairie
611 Blue grama-buffalo grass
613 Fescue grassland
614 Crested wheatgrass
701 Alkali sacaton-tobosagrass
702 Black grama-alkali sacaton
703 Black grama-sideoats grama
704 Blue grama-western wheatgrass
705 Blue grama-galleta
706 Blue grama-sideoats grama
707 Blue grama-sideoats grama-black grama
710 Bluestem prairie
711 Bluestem-sacahuista prairie
712 Galleta-alkali sacaton
715 Grama-buffalo grass
717 Little bluestem-Indiangrass-Texas wintergrass
719 Mesquite-liveoak-seacoast bluestem
720 Sand bluestem-little bluestem (dunes)
721 Sand bluestem-little bluestem (plains)
722 Sand sagebrush-mixed prairie
724 Sideoats grama-New Mexico feathergrass-winterfat
725 Vine mesquite-alkali sacaton
727 Mesquite-buffalo grass
730 Sand shinnery oak
731 Cross timbers-Oklahoma
732 Cross timbers-Texas (little bluestem-post oak)
735 Sideoats grama-sumac-juniper
802 Missouri prairie
803 Missouri glades
804 Tall fescue
809 Mixed hardwood and pine
Habitat: Cover Types
This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):
More info for the terms: cover, swamp
SAF COVER TYPES :
14 Northern pin oak
15 Red pine
20 White pine-northern red oak-red maple
25 Sugar maple-beech-yellow birch
26 Sugar maple-basswood
27 Sugar maple
28 Black cherry-maple
39 Black ash-American elm-red maple
40 Post oak-blackjack oak
42 Bur oak
46 Eastern redcedar
51 White pine-chestnut oak
52 White oak-black oak-northern red oak
53 White oak
55 Northern red oak
58 Yellow-poplar-eastern hemlock
59 Yellow-poplar-white oak-northern red oak
61 River birch-sycamore
62 Silver maple-American elm
65 Pin oak-sweetgum
66 Ashe juniper-redberry (Pinchot) juniper
67 Mohrs (shin) oak
73 Southern redcedar
88 Willow oak-water oak-diamondleaf (laurel) oak
89 Live oak
91 Swamp chestnut oak-cherrybark oak
92 Sweetgum-willow oak
93 Sugarberry-American elm-green ash
94 Sycamore-sweetgum-American elm
108 Red maple
110 Black oak
236 Bur oak
237 Interior ponderosa pine
241 Western live oak
Habitat: Plant Associations
This species is known to occur in association with the following plant community types (as classified by Küchler 1964):
More info for the term: shrub
KUCHLER  PLANT ASSOCIATIONS:
K016 Eastern ponderosa forest
K017 Black Hills pine forest
K018 Pine-Douglas-fir forest
K019 Arizona pine forest
K023 Juniper-pinyon woodland
K053 Grama-galleta steppe
K056 Wheatgrass-needlegrass shrubsteppe
K058 Grama-tobosa shrubsteppe
K059 Trans-Pecos shrub savanna
K060 Mesquite savanna
K061 Mesquite-acacia savanna
K062 Mesquite-live oak savanna
K063 Foothills prairie
K065 Grama-buffalo grass
K068 Wheatgrass-grama-buffalo grass
K069 Bluestem-grama prairie
K070 Sandsage-bluestem prairie
K073 Northern cordgrass prairie
K074 Bluestem prairie
K075 Nebraska Sandhills prairie
K076 Blackland prairie
K081 Oak savanna
K082 Mosaic of K074 and K100
K083 Cedar glades
K084 Cross Timbers
K085 Mesquite-buffalo grass
K086 Juniper-oak savanna
K087 Mesquite-oak savanna
K088 Fayette prairie
K089 Black Belt
K095 Great Lakes pine forest
K098 Northern floodplain forest
K099 Maple-basswood forest
K100 Oak-hickory forest
K101 Elm-ash forest
K102 Beech-maple forest
This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):
FRES10 White-red-jack pine
FRES21 Ponderosa pine
FRES32 Texas savanna
FRES33 Southwestern shrubsteppe
FRES36 Mountain grasslands
FRES38 Plains grasslands
This species is easily established from seed and the seed is commercially available through plant vendors. Germination of this species is rather poor without some type of scarification procedure. Mechanical scarification using sandpaper or a laboratory scarifier is acceptable. Purple prairie clover should be planted on a prepared, weed free, firm seedbed. The seedbed should be firm enough to allow planting at a 6 to 12 mm depth. Seed should be inoculated with the proper Rhizobium (Nitragin-type F) strain prior to planting.
Planting using a drill with depth bands and a legume box would provide good seed depth placement and seed to soil contact. The use of broadcast seeding will require a greater overall seeding rate to compensate for a less accurate delivery system. A normal seeding rate of 323 to 388 PLS seeds per square meter would have to be increased to accommodate a broadcast seeding.
Fischbach et al. (2005) found that in Minnesota in a seeding rate experiment that purple prairie clover had increased number of seedlings the year after establishment at all seeding rate levels tested. All legumes in the test had the highest percentage of seeds that develop into plants at the lowest seeding rate and the lowest seeds that develop into plants at the highest seeding rate. Launchbaugh and Owensby (1970), working with several native grass species, also noticed an inverse relationship between increased seeding rates and final plant establishment.
Flower-Visiting Insects of Purple Prairie Clover in Illinois
(Bees collect pollen or suck nectar; flies and beetles usually suck nectar, although some species may feed on pollen; other insects suck nectar; observations are from Robertson, Petersen, Moure & Hurd, Reed, and Smith et al. as indicated below)
Apidae (Apinae): Apis mellifera sn cp fq (Rb); Apidae (Bombini): Bombus affinis (Re), Bombus auricomus sn cp (Rb, Re), Bombus bimaculatus (Re, Smh), Bombus fervida (Pt, Re), Bombus fraternus sn cp fq (Rb, Smh), Bombus griseocallis sn cp fq (Rb, Re, Smh), Bombus impatiens sn cp fq (Rb, Re, Smh), Bombus pensylvanicus sn cp fq (Rb, Re, Smh), Bombus ternarius (Re), Bombus vagans (Re), Psithyrus variabilis sn (Rb); Anthophoridae (Anthophorini): Anthophora walshii sn (Rb); Anthophoridae (Ceratinini): Ceratina cockerelli (Smh), Ceratina dupla dupla sn cp (Rb); Anthophoridae (Epeolini): Epeolus bifasciatus sn (Rb), Triepeolus concavus sn fq (Rb), Triepeolus lunatus concolor sn fq (Rb), Triepeolus lunatus lunatus sn (Rb), Triepeolus remigatus sn (Rb), Triepeolus simplex sn (Smh); Anthophoridae (Eucerini): Melissodes agilis sn (Rb, Re, Smh), Melissodes bimaculata bimaculata sn cp fq (Rb, Re, Smh), Melissodes communis communis sn cp fq (Rb, Smh), Melissodes comptoides sn fq (Rb), Melissodes denticulata sn (Rb), Melissodes illata (Re), Melissodes tepaneca sn cp fq (Rb), Melissodes trinodis sn (Rb), Svastra obliqua obliqua sn cp fq (Rb), Svastra petulca (Smh), Synhalonia speciosa sn cp (Rb), Tetraloniella albata sn fq (Rb, Smh); Anthophoridae (Xylocopini): Xylocopa virginica sn fq (Rb, Smh); Megachilidae (Anthidiniini): Anthidiellum notatum (Smh); Megachilidae (Coelioxini): Coelioxys alternata alternata sn (Rb), Coelioxys germana sn (Rb), Coelioxys octodentata sn fq (Rb), Coelioxys rufitarsis rufitarsis sn (Rb, Re), Coelioxys sayi sn (Rb); Megachilidae (Megachilini): Megachile brevis brevis sn cp fq (Rb), Megachile georgica (Smh), Megachile inimica sayi sn (Rb), Megachile latimanus sn cp fq (Rb, Re), Megachile parallela parallela sn (Rb), Megachile petulans fq (Smh), Megachile xylocopoides (Smh); Megachilidae (Osmiini): Hoplitis cylindricus sn cp fq (Rb), Hoplitis pilosifrons sn cp (Rb, Smh); Megachilidae (Trypetini): Heriades leavitti sn cp (Rb, Smh)
Halictidae (Halictinae): Agapostemon sericea sn (Rb, Re), Agapostemon splendens sn (Rb, Re), Agapostemon texanus texanus sn (Rb, Re), Agapostemon virescens sn cp fq (Rb, Re), Augochlorella aurata sn cp fq (Rb, Smh), Augochlorella gratiosa fq (Smh), Augochlorella striata sn cp fq (Rb, Re), Augochloropsis metallica metallica sn cp fq (Rb, Re), Halictus confusus sn cp fq (Rb, Re), Halictus ligatus sn cp (Rb), Halictus parallelus sn cp fq (Rb, MH, Smh), Halictus rubicundus sn cp fq (Rb, Pt, Smh), Lasioglossum sp. (Re), Lasioglossum albipennis cp fq (Rb, Re), Lasioglossum cressonii (Re), Lasioglossum imitatum fq (Smh), Lasioglossum lineatulus (Re), Lasioglossum nymphaearum (Re), Lasioglossum paradmirandus (Re), Lasioglossum perpunctatus (Re), Lasioglossum pictus (Re), Lasioglossum pilosus pilosus sn cp (Rb, Re), Lasioglossum pruinosus sn (Rb), Lasioglossum rohweri (Re), Lasioglossum tegulare (Re, Smh), Lasioglossum versatus sn cp fq (Rb), Lasioglossum vierecki (Re); Halictidae (Nomiinae): Nomia nortoni nortoni sn (Rb); Colletidae (Colletinae): Colletes aberrans (Re), Colletes albescens sn cp olg (Rb), Colletes robertsonii sn cp olg fq (Rb, Smh), Colletes susannae cp olg (Re), Colletes wilmattae cp olg (Re); Colletidae (Hylaeinae): Hylaeus affinis (Re); Andrenidae (Andreninae): Andrena commoda (Re)
Sphecidae (Bembicinae): Bembix americana (Rb), Bembix nubilipennis (Rb), Bembix sayi (Re); Sphecidae (Philanthinae): Cerceris bicornuta (Rb), Philanthus sanbornii (Re), Philanthus ventilabris (Rb, Re); Sphecidae (Sphecinae): Ammophila kennedyi (Rb), Ammophila nigricans fq (Rb), Ammophila pictipennis (Rb), Ammophila procera (Rb), Eremnophila aureonotata (Rb), Prionyx atrata (Rb, Re), Prionyx thomae (Rb), Sphex ichneumonea (Rb); Vespidae (Eumeninae): Eumenes fraterna (Rb); Tiphiidae: Myzinum quinquecincta fq (Rb, Re); Scoliidae: Campsomeris plumipes (Rb)
Syrphidae: Allograpta obliqua sn (Rb), Eristalis stipator sn (Rb), Eristalis tenax (Re), Eupeodes sp. (Re), Helophilus latifrons sn (Rb, Re), Neocnemodon sp. (Re), Sphaerophoria contiqua sn (Rb, Re), Syrphus sp. (Re), Toxomerus geminatus (Re), Toxomerus marginatus sn (Rb, Re), Tropidia quadrata sn (Rb); Bombyliidae: Exoprosopa fasciata sn (Rb), Systoechus vulgaris sn (Rb), Villa sp. (Re); Conopidae: Physocephala texana sn (Rb), Thecophora occidensis sn (Rb), Zodion obliquefasciatum sn (Rb); Sarcophagidae: Ravinia anxia sn (Rb)
Lycaenidae: Everes comyntas sn (Rb); Pieridae: Colias cesonia sn (Rb), Colias philodice sn (Rb)
Hesperiidae: Pholisora catullus sn (Rb), Polites peckius sn (Rb), Polites themistocles sn (Rb)
Cerambycidae: Typocerus sinuatus sn (Rb); Chrysomelidae: Diabrotica sp. (Re), Diabrotica undecimpunctata sn (Rb); Meloidae: Epicauta atrata sn (Rb), Epicauta pensylvanica sn (Rb)
Miridae: Adelphocoris rapidus (Rb); Pentatomidae: Euschistus ictericus (Rb)
Fire Management Considerations
Fire severity affects purple prairie clover survivorship and postfire productivity. Bidwell and others [12,13] noted the effects of using a backing fire versus a headfire. In postfire year 1, abundance of forbs (including purple prairie clover) was 26% greater on backfired plots compared to headfired plots. This may be due to a reduction in interference from tallgrasses, such as prairie Junegrass and little bluestem, which are negatively affected by late spring burning. Also, backfires often create a mosaic of burned and unburned patches that may provide favorable microsites where purple prairie clover can escape lethal fire temperatures .
Broad-scale Impacts of Plant Response to Fire
Annual burning of prairie lands reduces available soil nitrogen
and increases competition among plants limited by nitrogen availability . Legumes including
purple prairie clover have the ability to fix
atmospheric nitrogen, and may have an advantage over other forbs and some grasses
in nitrogen-stressed environments .
Plant Response to Fire
Plant growth: Purple prairie clover may recover from fire by establishing from soil-stored seed and sprouting from the root crown. Purple prairie clover has responded favorably to prescribed fire in various studies [12,13,39,64]. Due to the hard seedcoat of legumes like purple prairie clover, these species' germination rates maybe enhanced by burning .
Towne and Knapp  noted that purple prairie clover that was top-killed by fire showed great capacity to sprout after fire. There is no specific information available on how quickly purple prairie clover recovers after burning. Further research is needed on this topic.
Productivity: Several studies have focused on how the frequency of burning relates to productivity of purple prairie clover. Generally, annual burning favors annual grasses and reduces the abundance of perennial forbs including purple prairie clover . Studies conducted in Minnesota in 1984  and Missouri in 1964  suggest that, compared to annual burning, biennial burning increases frequency and basal areas of legume species  including purple prairie clover . In Wisconsin prairie restoration projects where purple prairie clover has prospered, managers recommend a 5-year burning interval .
Burning can enhance flower productivity in several prairie forbs including purple prairie clover. Purple prairie clover produced a greater abundance of inflorescences after a single spring burn on a Minnesota prairie than prior to burning . The effects of this burn are attributed to the removal of litter and standing dead stems by the fire. Removal of litter allows for increased light intensities near the soil and thus higher soil temperatures, which enhance plant productivity. Litter reduces the presence and productivity of many forbs including purple prairie clover . For more on the effects of litter on purple prairie clover, see Management Considerations.
The Great Plains region where purple prairie clover commonly occurs is typical of prairie and savanna ecosystems that require fire to maintain historical ranges of species composition and species richness . Most of the available information has been based on short-term research . Long-term effects (beyond the scope of current research; >20 years) of various FIRE REGIMES are not well known.
Season of burning: Interactions between season of burn and purple prairie clover phenology are not well known . While spring burning generally decreases the immediate abundance of forb species that are actively growing , legume species including purple prairie clover in Kansas have shown increased growth and vigor 3 years following spring burns, nearly doubling stem biomass on upland sites and quadrupling stem biomass on lowland sites .
While most studies find that forb production is compromised after late spring burning, Bidwell and others [12,13] found that late spring backburning increased the productivity of purple prairie clover and other forb species (see Fire Management Considerations). Testing seasonal differences in annual prescribed annual burning on a Kansas prairie for 8 years, Towne and Kemp  found that legume species including purple prairie clover increased in cover in response to burning at any season. Greatest increases occurred 6 years after fire treatments, on autumn and winter prescribed burn plots. Others have found that most forbs including purple prairie clover decrease in abundance after being top-killed by late spring burning, while purple prairie clover increases after autumn and early spring burning [46,87].
The effects of mid-summer burning are not available in current literature (2005). For the purposes of restoration ecology, dormant-season fires probably do not resemble historical disturbance regimes found before European settlement. It is suspected that varied burn seasons, and intervals brought by natural ignitions from lightning prior to the European settlement era, produced greater levels of biodiversity and species assemblages than any single management method for native prairie lands . Unfortunately, information on purple prairie clover frequency and abundance prior to European settlement is not available.
Immediate Effect of Fire
POSTFIRE REGENERATION STRATEGY :
Caudex/herbaceous root crown, growing points in soil
Ground residual colonizer (on-site, initial community)
Fire adaptations: Purple prairie clover establishes from soil-stored seed after fire. While not specifically documented, it is implied that purple prairie clover root crowns may survive burning that consumes the aerial portions of the plant, allowing postfire sprouting from the root crowns . The large woody taproot allows for photosynthate and nutrient storage that can support postfire root crown sprouting. Additionally, fire creates favorable conditions (disturbed soil, decreased levels of mulch, reduced interference from forbs) that are favorable for purple prairie clover seedling establishment and growth [12,13,39,64].
FIRE REGIMES: Historically fire has been an important natural component of grassland communities where purple prairie clover occurs . Frequent, stand-replacement surface fires in plains grasslands and prairies affect species composition and vegetation dynamics . Across the Great Plains, lightning-caused and human-caused fires may have occurred as frequently as every 1 to 10 years for thousands of years prior to European settlement [67,117]. The implications of the cessation of historical FIRE REGIMES in the last century on purple prairie clover are unknown. Purple prairie clover has responded favorably to burning in several prescribed fire studies [12,13,39,64] using various annual intervals and seasons (see Plant Response to Fire).
In some habitats fire is necessary to maintain purple prairie clover. For example, along woodland-grassland ecotones in purple prairie clover's eastern range, the cessation of fire has caused encroachment of woody species that shade out purple prairie clover and reduce its abundance .
The following list provides fire return intervals for plant communities and ecosystems where purple prairie clover is important. It may not be inclusive. For further information see the FEIS reviews on the dominant species listed below.
|Community or Ecosystem||Dominant Species||Fire Return Interval Range (years)|
|sugar maple-basswood||Acer saccharum-Tilia americana||> 1,000 |
|bluestem prairie||Andropogon gerardii var. gerardii-Schizachyrium scoparium||67,79]|
|Nebraska sandhills prairie||A. gerardii var. paucipilus-S. scoparium||< 10|
|bluestem-Sacahuista prairie||A. littoralis-Spartina spartinae||79]|
|silver sagebrush steppe||Artemisia cana||5-45 [56,85,117]|
|sagebrush steppe||A. tridentata/Pseudoroegneria spicata||20-70 |
|basin big sagebrush||A. tridentata var. tridentata||12-43 |
|mountain big sagebrush||A. tridentata var. vaseyana||15-40 [5,23,75]|
|Wyoming big sagebrush||A. tridentata var. wyomingensis||10-70 (40**) [107,118]|
|plains grasslands||Bouteloua spp.||79,117]|
|blue grama-needle-and-thread grass-western wheatgrass||B. gracilis-Hesperostipa comata-Pascopyrum smithii||79,88,117]|
|blue grama-buffalo grass||B. gracilis-Buchloe dactyloides||79,117]|
|blue grama-tobosa prairie||Bouteloua gracilis-Pleuraphis mutica||79]|
|sugarberry-America elm-green ash||Celtis laevigata-Ulmus americana-Fraxinus pennsylvanica||109]|
|northern cordgrass prairie||Distichlis spicata-Spartina spp.||1-3 |
|black ash||Fraxinus nigra||109]|
|Ashe juniper||Juniperus ashei||79]|
|cedar glades||J. virginiana||3-22 [52,79]|
|wheatgrass plains grasslands||Pascopyrum smithii||79,85,117]|
|pine-cypress forest||Pinus-Cupressus spp.||4]|
|sycamore-sweetgum-American elm||Platanus occidentalis-Liquidambar styraciflua-Ulmus americana||109]|
|eastern cottonwood||Populus deltoides||79]|
|aspen-birch||P. tremuloides-Betula papyrifera||35-200 [38,109]|
|quaking aspen (west of the Great Plains)||P. tremuloides||7-120 [4,50,73]|
|Texas savanna||P. glandulosa var. glandulosa||79]|
|black cherry-sugar maple||Prunus serotina-Acer saccharum||> 1,000 |
|mountain grasslands||Pseudoroegneria spicata||3-40 (10**) [3,4]|
|bur oak||Quercus macrocarpa||109]|
|oak savanna||Q. macrocarpa/Andropogon gerardii-S. scoparium||2-14 [79,109]|
|Fayette prairie||S. scoparium-Buchloe dactyloides||109]|
|little bluestem-grama prairie||S. scoparium-Bouteloua spp.||79]|
More info for the terms: forbs, natural, sere, succession
Generally purple prairie clover is considered a mid- to late successional species . Purple prairie clover can also fill a pioneer role, as seen in roadsides and disturbed locations . The following is a general description of the successional pathways on prairie lands. Many details of succession in these associations remain unknown.
On the mixed-grass prairies of the southern Great Plains, purple prairie clover is part of a group of forbs found in late successional seres. A common pattern of succession in disturbed prairie regions begins with the dominance of native prairie annuals, nonnative annual weeds, and ragweeds (Ambrosia spp.), which may persist for 1 to 3 years. Soon following, a collection of nonnative and native grasses and perennial forbs, including purple prairie clover, create a mosaic of species that may take 15 to 40 years to develop, depending on environmental conditions and "competitive" factors. Common species that coexist with purple prairie clover in the tallgrass prairie during the later stages of succession include lead plant and prairie dropseed .
In its eastern range in forest openings where fires and other natural disturbances are suppressed, purple prairie clover can be shaded out by encroaching woody species . Purple prairie clover is thought to be an indicator of prairie in its later successional sere and may be an indicator of pristine prairie ecosystems .
Purple prairie clover reproduces by seed .
Breeding system: Purple prairie clover is cross pollinated . Mating system is primarily xenogamous, but self-pollination also occurs. In a Wisconsin prairie study, 45% of hand-pollinated, outcrossed flowers produced large, viable seeds, and 19% of selfed flowers produced seeds. Native bees and honeybees were pollinators .
Seed production is highest with favorable soil moisture and nutrient conditions. A survey of native plant horticulturists in Minnesota indicated that purple prairie clover frequently produces low seed yields . Another Minnesota study compared the phenological development of purple prairie clover in cultivated fields to noncultivated managed prairie. Cultivated fields produced 3 times as much seed as noncultivated prairie. Seed and inflorescence production on cultivated and noncultivated native prairie were :
|Item||Cultivated Fields||Noncultivated Prairie|
|Number of inflorescences initiated/plant||35.0||29.1|
|Number of seeds/inflorescence||33.5||11.5|
|Seed weight/plant (g)||0.49||0.22|
|Number of seeds/plant||379.8||173.4|
Cultivated fields were devoid of any other competing plants, fertilized, and only contained evenly spaced transplanted purple prairie clover plants from native prairie lands. The noncultivated, native prairie had a variety of other forb and grass species. The noncultivated prairie was under a regimen of prescribed fire every 2 to 3 years. Season of burning was not described . Stevens  found that a single purple prairie clover plant may produce 368 seeds per plant (many of which may not mature), with seeds weighing 1.5 g/1,000 seeds.
Seed dispersal: Neither fruits nor seeds have specialized means of dispersal; thus, most seed falls near the parent plant . A seed dispersal study using purple prairie clover and other seed in cattle feed showed that following ingestion, cattle were inefficient vectors for dispersing viable purple prairie clover seed .
Seed banking: Purple prairie clover has soil-stored seed , but further studies are needed on the relative importance of seed banking to purple prairie clover regeneration. A study on native Kansas prairie found low numbers of buried viable purple prairie clover seed .
Germination: Purple prairie clover germinates at soil temperatures ranging from 59 to 86 Â°F (15-30 Â°C)  while temperatures as low as 41 Â°F (5 Â°C) have broken dormancy . A survey of native plant horticulture in Minnesota indicated low rates of germination of purple prairie clover . Germination of purple prairie clover is enhanced by scarification, disturbing the litter and duff layers to expose soil, and stratification [14,100].
Seedling establishment/growth: Bjugstand and Whitman  used several varieties of forbs for reclamation of strip-mined land and found that purple prairie clover showed "excellent" germination and subsequent "vigorous" growth in the greenhouse. Purple prairie clover transplanted to reclamation areas continued to show excellent vigor and growth .
Asexual regeneration: The ability of purple prairie clover to regenerate vegetatively is unclear. Meier and Weaver  state that purple prairie clover does not reproduce asexually. However, Towne and Knapp  suggest that purple prairie clover sprouts from the root crown following top-kill by fire. Further research is needed on the ability of purple prairie clover to regenerate asexually.
Growth Form (according to Raunkiær Life-form classification)
More info for the term: hemicryptophyte
RAUNKIAER  LIFE FORM:
Life History and Behavior
More info for the terms: forb, warm-season
Purple prairie clover is a warm-season forb that generally germinates during spring . In May to August (depending on climate and geographic location), purple prairie clover produces several to many inflorescences. Average flowering dates for purple prairie clover from 5 years of observation in North Dakota were :
Earliest 1st bloom
Latest 1st bloom
Median date of full flowering
Median date when 95% of flowering complete
Flowering period (days)
|June 17th||July 13th||July 15th||August 15th||35|
Flowering dates for purple prairie clover are influenced more by temperature than precipitation. Warmer temperatures seem to promote earlier flowering, while warm temperatures and ample moisture in summer increase the duration of blooming . Purple prairie clover seed matures in most locations from August to September . In Minnesota seed development from anthesis to seed maturity took 15 weeks .
Molecular Biology and Genetics
Barcode data: Dalea purpurea
Statistics of barcoding coverage: Dalea purpurea
Public Records: 3
Specimens with Barcodes: 11
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: N5 - Secure
Rounded National Status Rank: N5 - Secure
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status (e.g. threatened or endangered species, state noxious status, and wetland indicator values).
Pests and potential problems
Grasshoppers and small rodents in moderate numbers can cause damage to seedling stands.
Low- to moderate grazing pressure may enhance purple prairie clover production
by removing vegetative cover , but overgrazing can decrease coverage and frequency of purple prairie
clover . In Illinois, populations of purple prairie clover have recovered in areas where
they had been removed
under high grazing pressure . In Iowa, purple
was 1 species in a large group of native forbs that decreased or disappeared
under unspecified grazing pressure .
In prairies near forest lands, encroachment of forest species
into grasslands changes vegetation structure and composition. In eastern Nebraska, eastern redcedar encroachment
into prairies has been linked to the decline of many prairie species, including
purple prairie clover, due to shading .
The accumulation of litter on prairies affects purple
populations. In Kansas, purple prairie clover decreased during a 50-year study on
tallgrass prairie that has seen a shift
from summer haying to spring biannual burning. The author speculates that these
decreases resulted from the cessation of mid-summer
mowing. In this study mowing was thought to be responsible for the removal
of biomass during the summer months, altering microhabitat conditions that had
supported purple prairie clover. The
increase of mulch thickness may explain decreases in purple
prairie clover and
other native forbs . In a study of the effects of cessation of mowing and
introduction of prescribed fire, forbs including purple prairie
clover increased in abundance due to the reduction of mulch . For more on the effects of litter on purple prairie clover,
see Fire Effects
Experimental research on effects of small rodent herbivory on native forb populations
found that herbivory by meadow voles reduced purple prairie clover density [59,77]. Whether or not
these findings in laboratory communities were applicable to prairie
communities was unclear.
Cultivars, improved and selected materials (and area of origin)
Contact your local Natural Resources Conservation Service office for more information. Look in the phone book under ”United States Government.” The Natural Resources Conservation Service will be listed under the subheading “Department of Agriculture.”
‘Kaneb’ purple prairie clover was released by the Manhattan, Kansas Plant Materials Center in 1975 in cooperation with the Nebraska Agriculture Experiment Station in Lincoln, Nebraska. It was first collected in 1948 in a native grassland area in Riley County, Kansas. Testing indicated it was superior in stand, height and vigor to other collected accessions. This accession was also grown and tested at SCS Plant Materials Center’s in North Dakota and New Mexico. Foundation seed is maintained by the Manhattan Plant Materials Center.
Bismarck Germplasm is a selected class release from the Bismarck, North Dakota Plant Materials Center. It was collected originally in 1975 in Lyman County, South Dakota by Tom Pozarnsky. Bismarck was compared to ten purple prairie clover accessions and was selected for its superior vigor, forage abundance and above average seed yield. Generation 1 seed is maintained by the Bismarck Plant Materials Center and is available in limited quantities for commercial seed increase.
Central Iowa Germplasm is a source identified release from the Elsberry, Missouri Plant Materials Center. It is a composite of collections of purple prairie clover made through out central Iowa. Breeder’s seed is maintained by the Elsberry Plant Materials Center and the University of Northern Iowa (UNI) at Cedar falls, Iowa. Source identified seed will be available to interested seed producers.
McGraw et al. (2004) determined seed production potential by measuring the weight of seeds per plant and the number of seeds per plant. Purple prairie clover which produced only 2.1 g of seed per plant, produced as many seeds per plant as the top three legumes due to its relatively smaller seed size. Purple prairie clover averaged 698 seed per gram which yields 698,000 seeds per kilogram which would be 317,000 seeds per pound for this species. Seed can be collected by hand stripping pods from mature plants and then hammer milling and re-cleaning in a fanning mill. Field size stands can be harvested with a standard combine and then cleaned in a fanning mill.
Five year average seed yields at Manhattan Plant Materials Center (PMC) were 136.5 kg per hectare. Purity of harvested, processed seed is typically 99 percent or better with a germination range of 36 to 83 percent (including germination and hard seed). A long term seed storage study conducted by the Manhattan PMC indicates that ‘Kaneb’ purple prairie clover can be stored successfully under ideal (cool and dry) conditions for up to 26 years and retain good germination. Kaneb’s initial germination was 81 percent and after 26 years of storage the germination result was still 77 percent. There was however, a much lower percentage of hard seed in the latest test results when compared to the initial test results.
Purple prairie clover does not spread aggressively by seed or vegetatively (Platt and Harder 1991).
Weed control during establishment of native forbs is essential to produce healthy plant stands. Mowing at a height that will not affect purple prairie clover seedlings is one method of reducing weed competition. Masters et al. (1996) found that the use of Imidazolinone herbicides was successfully used to establish purple prairie clover. Irrigated and non-irrigated plots of purple prairie clover experienced greater foliar cover when treated with herbicides when compared to non-herbicide treated plots (Masters et al. 1996).
McGraw et al. (2004) found that while purple prairie clover tended to have good forage quality, it had relatively poor forage yields when compared to other native legumes. Posler et al. (1993) found that the influence of purple prairie clover was positive on forage digestibility when compared to values for grasses alone. They concluded that the use of mixtures of purple prairie clover with adapted warm-season grasses as forage crops appeared promising.
Relevance to Humans and Ecosystems
Value for rehabilitation of disturbed sites
Purple prairie clover is commonly found in seed mixtures recommended for revegetation, reclamation [34,93], and native prairie restoration projects . Gustafson and others  found that by using several local seed sources of purple prairie clover for restoration projects, local gene pools were maintained and regional genetic diversity was enhanced, promoting persistence and vigor in restored purple prairie clover populations. Purple prairie clover is frequently used in seed mixes for erosion control due to its ability to establish on disturbed sites and its capability to condition soil with nitrogen . Legumes such as purple prairie clover fix atmospheric nitrogen in the soil. They may have an advantage over forbs and some grasses in degraded prairie or pasture sites [24,62].
Propagation: Purple prairie clover germination is enhanced in scarified soils . Purple prairie clover in its natural habitat is often found in disturbed locations such as black-tailed prairie dog towns  and on dug mounds created by American badgers . Stratification  and inoculation with rhizobium  have increased germination success of purple prairie clover in the laboratory. Purple prairie clover has been successfully used in several roadside vegetation projects throughout the Great Plains [28,33]. In a strip-mine reclamation project, purple prairie clover demonstrated excellent success as a colonizer, exhibiting high rates of germination and subsequent vigorous seedling growth in the greenhouse and afterwards during transplanting .
Purple prairie clover is highly dependent upon mycorrhizal fungi. A mycorrhizal inoculation study found prairie species uptake and transport of soil nutrients such as phosphorus and zinc was enhanced by mycorrhizae, but the study did not show any substantial effects on purple prairie clover seedling emergence . Conversely, a study that used a benomyl (a fungicide specifically for the removal of mycorrhizae in soils) considerably lowered survivorship of purple prairie clover .
Purple prairie clover is susceptible to interference from with exotic species during establishment due to its relatively slow rate of seedling growth compared to that of nonnative invasive species. In North Dakota some populations of purple prairie clover have been completely eliminated by infestations of leafy spurge (Euphorbia esula) . Reducing weed interference using herbicide applications (imazethapyr + imazapic) has been successful in improving establishment of purple prairie clover in Nebraska .
Importance to Livestock and Wildlife
Purple prairie clover produces excellent forage for livestock and wildlife. When abundant on pasture lands it may be an important component in hay [62,100]. Purple prairie clover is recommended for use in restoration seed mixtures. It produces forage with high yields, extended grazing periods, and increased nutritional values [84,90]. Pronghorn graze purple prairie clover on summer ranges of Montana . A 2-year study in Minnesota found that white-tailed deer did not browse purple prairie clover , although this does not imply that deer and other ungulates never graze this species.
In North Dakota, crude protein levels of purple prairie clover ranged from 12% in June to 8% in August . Due to its high palatability and high concentrations of nutritional protein, purple prairie clover is generally considered one of the most important legumes in native grasslands on the Great Plains, although some rare instances of bloat have been reported in livestock [62,100]. Crude and digestible protein content of purple prairie clover are as follows :
|domestic goats||9.7 %|
|domestic rabbits||9.6 %|
|domestic sheep||10.1 %|
Cover value: No information is available on this topic.
Other uses and values
This leguminous forb produces excellent forage for livestock and wildlife. It is high in protein and highly palatable, although it may cause bloat. (Stubbedieck and Conard 1989) This species will decrease and disappear under persistent overgrazing. It is an important legume in native grasslands because of nitrogen fixation. Purple prairie clover is used in seed mixtures for re-vegetation and prairie restoration. It is a potentially useful plant for roadside and rest area beautification, park plantings and recreational garden natural area plantings. This species is also used in mixtures on dam face structures and critical area plantings. Native Americans ate fresh and boiled leaves of purple prairie clover. Bruised leaves were steeped in water and applied to fresh, open wounds. Ponca Indians chewed the roots for their pleasant flavor and made tea from the leaves. Pawnee Indians used the bundled stems to make brooms. (Stubbendieck et al. 1989).
Dalea purpurea is a species of flowering plant in the legume family known by the common name purple prairie clover, better written as "prairie-clover," in recognition of the fact that it is not a true clover (genus Trifolium). It is native to central North America, where it occurs from central Canada to the southeastern and southwestern United States, except for the east and west coasts. It is a common and widespread plant within its range, especially on the Great Plains.
This plant is a perennial herb growing 20 to 90 centimetres (7.9 to 35.4 inches) tall. The mature plant has a large taproot which may grow two meters deep. The stem is woody with several branches. The leaves are a few centimeters long and are divided into 3 to 7 narrow leaflets. The inflorescence atop each stem branch is a spike up to 7 cm (2.8 in) long containing many purple flowers. The fruit is a legume pod containing 1 or 2 seeds.
This plant is a common member of the flora on the plains of central North America, occurring in a variety of habitat types, including several types of grassland. It occurs in glades, riverbanks and floodplains, oak woodlands, pinyon-juniper woodlands, shrubsteppe, many types of forests, and the Sand Hills of Nebraska. It occurs in a variety of prairie ecosystems. On tallgrass prairie it is associated with plants such as little bluestem (Schizachyrium scoparium), big bluestem (Andropogon gerardii), prairie Junegrass (Koeleria macrantha), prairie dropseed (Sporobolus heterolepis), lead plant (Amorpha canescens), and silky aster (Symphyotrichum sericeum). On midgrass prairie it grows alongside several grasses such as silver bluestem (Bothriochloa saccharoides), purple threeawn (Aristida purpurea), sideoats grama (Bouteloua curtipendula), and sand dropseed (Sporobolus cryptandrus). On shortgrass prairie it is associated with grasses such as blue grama (Bouteloua gracilis), hairy grama (B. hirsuta), and buffalo grass (B. dactyloides). This species may be considered an indicator of pristine prairie.
This species is used for revegetation efforts on reclaimed land, such as land that has been strip mined. It is good for preventing erosion and for fixing nitrogen in soil. Though it is often found in mid- to late-successional stages of ecological succession, it may also be a pioneer species, taking hold in bare and disturbed habitat, such as roadsides.
Purple prairie clover provides food for a number of animals, such as pronghorn. It also grows in cultivated fields and becomes included in hay for livestock. It is nutritious and is "considered one of the most important legumes in native grasslands on the Great Plains." It also had a number of uses for Native Americans. The leaves are edible and good for making tea and medicines, and the roots are palatable when chewed. The stems were used as brooms by the Pawnee people.
Dalea purpurea has been found to contain several active constituents, including pawhuskin A, pawhuskin B, pawhuskin C, and petalostemumol. The pawhuskins possess affinity for the opioid receptors, and pawhuskin A, by far the most potent of the group, acts as a non-selective antagonist of all three opioid receptors, with preference for the κ- and μ-opioid receptors over the δ-opioid receptor.
|Wikimedia Commons has media related to Dalea purpurea.|
- "Dalea purpurea Vent.". The Plant List.
- Dalea purpurea at NatureServe.org. Retrieved 11-25-2011.
- Dalea purpurea. Germplasm Resources Information Network. Retrieved 11-14-2011.
- Dalea purpurea. USDA Plants Profile. Retrieved 11-14-2011.
- Dalea purpurea. The Nature Conservancy. Retrieved 11-14-2011.
- League, Kevin R. 2004. Dalea purpurea. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Retrieved 11-14-2011.
- Belofsky G, French AN, Wallace DR, Dodson SL (January 2004). "New geranyl stilbenes from Dalea purpurea with in vitro opioid receptor affinity". J. Nat. Prod. 67 (1): 26–30. doi:10.1021/np030258d. PMID 14738380.
- Neighbors JD, Buller MJ, Boss KD, Wiemer DF (November 2008). "A concise synthesis of pawhuskin A". J. Nat. Prod. 71 (11): 1949–52. doi:10.1021/np800351c. PMID 18922035.
- Hartung AM, Beutler JA, Navarro HA, Wiemer DF, Neighbors JD (February 2014). "Stilbenes as κ-selective, non-nitrogenous opioid receptor antagonists". J. Nat. Prod. 77 (2): 311–9. doi:10.1021/np4009046. PMID 24456556.
Names and Taxonomy
purpurea Vent. (Fabaceae). Recognized varieties are as follows
D. purpurea var. arenicola (Wemple) Barneby
D. purpurea var. purpurea
violet prairie clover
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