Asclepias purpurascens L. purple milkweed State Distribution Photo by Michael R. Penskar Best Survey Period Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Legal status: State threatened one or two additional umbels are present in the upper leaf axils. The individual flowers, which are usually Global and state rank: G4G5/S3 from 13-17 mm long, bear reflexed, purplish corolla lobes that are glabrous (smooth), pale purple hoods Family: Asclepiadaceae (milkweed family) (forming the corona) 5-7 mm long, and incurved flat horns that are shorter than the hood. The reproductive Total range: Asclepias purpurascens is found parts (filaments, anthers, and style) are fused into a principally in eastern North America, occurring from structure called the gynostegium. The fruit is a smooth New Hampshire south to Virginia and ranging west to follicle (a pod) filled with seeds attached to downy hairs Wisconsin, Iowa, Kansas, and Oklahoma. (coma) that aid in wind dispersal. State distribution: Purple milkweed is known from Asclepias purpurascens is often difficult to distinguish more than 60 occurrences in southern Michigan; thirty- from the very similar looking common milkweed, four of these records are derived from collections made Asclepias syriaca, which despite its unfortunate prior to 1930. This species is concentrated primarily Latin epithet is also a native milkweed. Overall, the in southeastern and southwestern Lower Michigan, leaves of A. purpurascens are more acute and less where it is known from 19 counties, with most counties predominately pinnately–veined (i.e. more strongly tallying only a single occurrence. Counties with the net-veined) than A. syriaca. In addition, A. syriaca bears most occurrences are Washtenaw (10), St. Clair (9), and umbels in three or more leaf axils, with flowers that Jackson (8). The most northern location is Midland have hairy corolla lobes and hoods 3.5-5 mm long. County. There have been collections from St. Clair and Jackson counties that suggest the possibility of hybridization Recognition: Asclepias purpurascens stands erect on between these two species. stout, puberulent (short-hairy) stems, ranging to about 1 meter in height. Like other species of milkweed, the Best survey time/phenology: Surveys are best sap is a milky latex that readily bleeds from bruised or conducted during the flowering and fruiting periods, cut foliage and stems. The 10-15 cm long leaves are which occur from late June to August. opposite and elliptic to ovate-oblong, hairy beneath, and end in acute tips. At their base, the leaves are Habitat: This species is found primarily in dry soils broadly tapered to petioles that range from about 1-2.5 in prairies, including lakeplain prairies, and within cm. The inflorescence consists of atight umbel of open woodlands (especially oak and oak-pine), shrub purplish-red flowers borne terminally; occasionally, thickets, and on shores. Commonly associated species Michigan Natural Features Inventory P.O. Box 30444 - Lansing, MI 48909-7944 Phone: 517-373-1552 purple milkweed, Page 2 include such plants as big bluestem (Andropogon Research needs: Perhaps the principal need at the gerardii), little bluestem (Schizachyrium scoparius), present is experimental restoration management of blazing star (Liatris spicata),ironweed (Vernonia prairies and oak savannas to determine the most missurica), culver’s root (Veronicastrum virginicum), appropriate treatments (e.g. prescribed burning regimes) Indian grass (Sorghastrum nutans), tall coreopsis for perpetuating habitat. Demographic work on (Coreopsis tripteris), yellow loosestrife (Lysimachia populations and life history studies would also assist ciliata), mountain mint (Pycnanthemum virginianum), land managers. Riddell’s goldenrod (Solidago riddellii), field milkwort (Polygola sanguinea), Seneca snakeroot (Polygala Related abstracts: Lakeplain wet prairie, lakeplain polygama), creeping cinquefoil (Potentilla simplex), wet-mesic prairie, appressed bog clubmoss, eastern riverbank grape (Vitis riparia), red ash (Fraxinus prairie fringed-orchid, purple milkweed, Sullivant’s pennsylvanica), gray dogwood (Cornus foemina), and milkweed, blazing star borer, culver’s root borer, red- dogbane (Apocynum cannabinum). In lakeplain prairie legged spittlebug. regions, purple milkweed may grow with such rare species as Sullivant’s milkweed (Asclepias sullivantii), Selected references: Clinton’s bulrush (Scirpus clintonii), Gattinger’s gerardia (Agalinis gattingeri), and Skinner’s agalinis Voss, E.G. 1996. Michigan Flora. Part III. Dicots (Agalinis skinneriana). (Pyrolaceae-Compositae). Bull. Cranbrook Inst. Sci. 61 & Univ. of Michigan Herbarium. xix + 622 Biology: Asclepias purpurascens is a perennial arising pp. from a stout root. It flowers in June and July and fruit development occurs through August. As in other Woodson, R.E., Jr. 1954. The North American species species of Asclepias, the flowers are highly modified of Asclepias L. Ann. Miss. Bot. Gard. 41:1-208. for insect pollination. Adjacent anthers are joined together by two arms (translators) to a gland known as the corpusculum. Each half-anther contains pollen Abstract Citation: grains united into a waxy mass termed the pollinium. The pollinia are situated behind the hood, with the Choberka, E.G., M.R. Penskar, and P.J. Higman. 2000. translator arms and gland visible between the corona. Special plant abstract for Asclepias purpurascens During pollination an insect removes a pair of pollinia (purple milkweed). Michigan Natural Features by snagging them – via the sticky corpusculum — on Inventory, Lansing, MI. 2 pp. a spur of its leg as it visits the milkweed flower. The pollinia must be reinserted in a precise fashion in vacant slots behind the hood of another flower in order to effect pollination. Conservation/management: Purple milkweed is found in numerous counties in southern Lower Michigan, yet its status at many sites is unknown. Surveys to determine the status of this species at historical sites would enable a more reliable statewide assessment to be made, in order to determine if elevation to threatened or endangered status has merit. The primary conservation strategy for this species at the present time, in addition to status surveys, is the protection of prairie remnants and other dry open sites, as well as prairie restoration management, and prescribed burns to perpetuate suitable habitat in known sites. Updated April 2009. Comments: Milkweed floss was used throughout World Copyright 2004 Michigan State University Board of Trustees. War II for stuffing life-preserver jackets. The amount of Michigan State University Extension is an affirmative-action, equal- milkweed harvest in 1943 in Emmet Co MI, was almost opportunity organization. 200 tons of pods (Voss 1996). Milkweed has other commercial uses such as latex (rubber), fiber, or even Funding for abstract provided by Michigan Department of Natural fuel. Resources-Forest Management Division and Wildlife Division. Michigan Natural Features Inventory P.O. Box 30444 - Lansing, MI 48909-7944 Phone: 517-373-1552 Asclepias sullivantii Engelm. Sullivant’s milkweed State Distribution Best Survey Period Photo by Michael R. Penskar Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Legal status: State threatened ered exotic), both having broadly ovate, opposite leaves, milky sap, and dense, globe-like clusters of Global and state rank: G5/S2 flowers borne from upper leaf axils. However, mature leaves of A. sullivantii are distinguished by their Other common names: smooth milkweed, prairie reddish midveins, slightly undulate margins, milkweed somewhat acute tips, and complete lack of hair on Family: Asclepiadaceae (milkweed) the leaf underside. In addition, the leaves of Sullivant’s milkweed are usually strongly upswept Total range: This prairie species is concentrated in (see photo). In contrast, common milkweed has the Midwest, ranging north to Minnesota, east to relatively blunt-tipped leaves that are densely pubes- southern Ontario and Ohio, west to Nebraska, Kansas, cent beneath and remain roughly perpendicular to the and south to Oklahoma. It is considered rare in Minne- stem. The flowers of A. sullivantii are also larger, sota, Wisconsin, and Ontario, and is known only from fewer, and pale to strongly pink-purple in color, historical records in North Dakota. whereas those of A. syriaca are pink to dark purple, markedly smaller, and tend to be much more numerous State distribution: Sullivant’s milkweed is known in very dense inflorescences. The fruit of Sullivant’s from a total of 16 sites, with the majority of localities milkweed, a greenish-capsule termed a follicle, is occurring in Monroe and St. Clair counties. Oakland, relatively smooth in contrast to the warty follicle Wayne, Lenawee, and Tuscola counties all tally a produced by common milkweed. single occurrence each. Although this species was reported by Davis (1906) to be “very abundant” in the Sullivant’s milkweed could be confused with stems of lakeplain prairies of Tuscola County, extensive sur- common dogbane (Apocynum), especially the species veys there in recent years have failed to discover a known as Indian hemp (A. cannabinum). Dogbane can single surviving colony. A Berrien County report (M. be distinguished by its less robust growth habit, Kohring, pers. comm.) remains unconfirmed. Several narrower leaves, dark stem, and especially its fruit, of Michigan’s colonies consist of small numbers of which consists of pairs of long, dangling, skinny individuals persisting in highly