woolly milkweed

(Asclepias lanuginosa)

Conservation Status


No image available

  IUCN Red List

not listed


N4? - Apparently Secure


not listed


Woolly milkweed is a 6 to 12 tall, weekly erect, perennial forb that rises on a single stem. The leaves and stems contain a milky juice.

The stem is covered with long, soft shaggy, but unmatted hairs.

The leaves are alternate, lance-shaped, 1½ to 2¾ long, and have blunt tips. They are sparsely covered with long, soft shaggy, but unmatted hairs on both sides. The margins are untoothed, thickened, and rough to the touch.

The inflorescence is a single dense, umbrella-shaped cluster (umbel) at the end of the stem. The cluster is erect or drooping on a short stalk.

The structure of the typical milkweed flower is unique and instantly recognizable. There are 5 petals bent backward at the base and hanging downward. Subtending the petals are 5 much shorter, light green, lance-shaped sepals. There are 5 stamens. Formed from the filament of each stamen is a petal-like appendage. The appendage consists of a tubular hood surrounding an awl-shaped horn in the center of the hood. The stamens and the stigma are fused together into a crown-like structure (gynostegium). Each stigma has a long slit designed to catch the legs of a pollinating insect. A small, dark, sticky gland above this slit is attached to pollen sacs from adjacent anthers. These glands are designed to break off as an insect pulls its leg free of the slit, and remain attached to the insects leg. The flowers are pollinated by larger insects strong enough to lift off with the pollen sacs attached. Smaller insects are caught in a death trap or leave behind their detached legs.

The flowers of this plant are shaped like the typical milkweed flower. They are ¼ to tall, wide, and are attached on ¼ to ½ long thread-like stalks. The petals are greenish-yellow or somewhat purplish. They bend backward at the base, hang downward, then curl upward near the tip. They are attached directly below the hoods without a separating column. The hoods are the same color as the petals. They have no horns.

The fruit is a spindle-shaped pod. It opens on one side exposing the seeds to spreading by the wind. The seeds have a tuft of whitish hairs at the tip.




6 to 12


Flower Color


Greenish-yellow or somewhat purplish


Similar Species




Dry. Prairies, upland woods.




June to July


Faunal Associations


Milkweeds are the only plants that Monarchs lay their eggs on. The eggs are laid on the underside of healthy young leaves.




This and other milkweeds contain cardiac glycosides and may be poisonous to both humans and livestock.


Pests and Diseases






Distribution Map



2, 3, 4, 5, 28, 29, 30.









  Kingdom Plantae (green algae and land plants)  
  Subkingdom Viridiplantae (green plants)  
  Infrakingdom Streptophyta (land plants and green algae)  
  Superdivision Embryophyta (land plants)  
  Division Tracheophyta (vascular plants)  
  Subdivision Spermatophytina (seed plants)  
  Class Magnoliopsida (flowering plants)  
  Superorder Asteranae  


Gentianales (gentians, dogbanes, madders, and allies)  


Apocynaceae (dogbane)  
  Subfamily Asclepiadoideae (milkweeds)  
  Tribe Asclepiadeae  
  Subtribe Asclepiadinae  


Asclepias (milkweeds)  

Subordinate Taxa






Acerates lanuginosa

Asclepias otarioides

Asclepias scheryi


Common Names


hairy milkweed

side-cluster milkweed

sidecluster milkweed

woolly milkweed










The upper angle where the leaf stalk meets the stem.



A crown-like structure of plants of the genus Asclepias formed by the fusion of the anthers with the stigmas.



Long, straight, and narrow, with more or less parallel sides, like a blade of grass.



A flat-topped or convex, umbrella-shaped cluster of flowers or buds arising from more or less a single point.

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Other Videos
  Ascepias lanuginosa 8 17 13
Kevin Kawula

Published on Aug 20, 2013

A small patch of rare Woolly Milkweed at Lone Rock Prairie out side of Footville Wisconsin. Hill prairie with limestone over sandstone. Most plants were browsed (clipped) in early August, probably by small rodents.

  Endangered Woolly Milkweed on Illinois Prairie
Frank Zimmerman

Uploaded on Jun 27, 2011

One of the last 7 naturally occuring populations of wooly milkweed in the tallgrass prairie state of Illinois on a hot Spring day. The plants are all under 10 inches in height.

  Woolly Milkweed - Asclepias lanuginosa - July 2013 Lone Rock Prairie
Kevin Kawula

Published on Jul 21, 2013

Note: Shaky handheld footage as field note - Woolly Milkweed plants at Lone Rock Prairie (Footville), in western Rock County Wisconsin. A small patch 3 feet wide by 8 feet long, with 20 to 30 plants. Broken and eroded limestone over sandstone hill prairie. Eroded formations with older than Wisconsin era glacial till. Amorpha, Tradescantia, Tephrosia, Liatris aspera, Stipa associates




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