PROTECTING WISCONSIN'S BIODIVERSITY

 
 
   
 
Scientific Name Common Name Global Rank State Rank Federal Status WI Status

Purple Milkweed (Asclepias purpurascens)

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Photo by Thomas Meyer

 

Counties with Mapped NHI Occurrences

Purple Milkweed (Asclepias purpurascens), a Wisconsin Endangered plant, is found in open oak forests, forest margins, and roadsides. Blooming occurs early-June through late-July, fruiting early-July through late-August. The optimal identification period for this species is late-June through late-July.

 
 
 

Purple milkweed is an erect forb, up to 2m tall, with one terminal flower head with one or two additional flower heads in the upper part of plant. Flowers are bright pink to purple, reflexed, with glabrous corolla lobes, pale purple hoods 5-7mm long, and incurved flat horns that are shorter than the hood. Fruits are downy pods. Leaves are opposite, elliptic to ovate, 10-15cm in length with acute tips, and hairy on the underside with 8-25mm petioles.

It can be distinguished from other milkweeds by its bright pink to purple, mostly terminal flowers containing reflexed, glabrous corolla lobes (vs pubescent in A syriaca). The leaves are hairy below and usually more acute than the rounded leaves of A syriaca and less pinnately veined.

Rhizomatous. Blooming occurs early-June through late-July, fruiting early-July through late-August.

Perennial. The optimal identification period for this species is late-June through July.

Associated species include Quercus alba, Q velutina, Q macrocarpa.

Purple milkweed has wide soil moisture tolerances and is found in open oak forests, forest margins, and roadsides.

Avoid known individual plant locations and conduct operations elsewhere when they are least likely to cause damage. Ideally, this would involve frozen, snow-covered ground. However, in areas of the state where frozen conditions are unreliable, very dry soils late in the growing season might be the best available alternative. Consult with a biologist, if needed.

Avoid broadcast spraying of herbicides and use care with spot spraying.

Avoid site preparation that heavily disturbs herbaceous ground layer and soil, including bulldozing and furrowing, as well as grubbing and stump removal.

Prescribed burns and/or brushing may be beneficial, dependent on local site conditions and burn frequency. Rotational burns with annual unburned refugia may be preferred.

Maintain and restore open habitat through selective clearing and brushing.

Species of Greatest Conservation Need (SGCN) are associated with habitats (or natural communities) and places on the landscape. Understanding relationships among SGCN, natural communities and ecological landscapes help us make decisions about issues affecting SGCN and their habitat and how to respond. Download the Wildlife Action Plan association score spreadsheet to explore rare species, natural communities and ecological landscape associations

Conservation actions respond to issues or threats, which adversely affect species of greatest conservation need (SGCN) or their habitats. Besides actions such as restoring wetlands or planting resilient tree species in northern communities, research, surveys and monitoring are also among conservation actions described in the Wisconsin Wildlife Action Plan because lack of information can threaten our ability to successfully preserve and care for natural resources.