Asclepias speciosa

Native to West-central and Western United States and Canada, including North Dakota and South Dakota. Introduced in Minnesota; adventive.

Moist. Prairies.

June to August

Pink or reddish purple

1′ to 3′

This is an erect, perennial forb that rises from a deep rhizome. It often forms colonies. The leaves and stems are velvety and contain a milky juice.

The stems are erect, usually unbranched, and hairy.

The leaves are opposite, untoothed, 2½″ to 8″ long, up to 4″ wide, and egg-shaped. They have pointed tips and rounded bases. They are attached to the stem on short leaf stalks. There are conspicuous veins running from the midrib to the edge. The lower surface is hairy.

The inflorescence is one or more loose, umbrella-shaped clusters (umbels) rising from the upper leaf axils and at the end of the stem. The clusters are 2″ to 3″ in diameter and are on a 1″ to 3″ long, woolly, stalk. They typically have 10 to 20 flowers.

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 but are larger than those of any other milkweed. They are ¾″ to 1½″ tall, ½″ to 1⅛″ wide, and are attached on ⅜″ to 1⅛″ long stalks. The petals are pink or reddish purple. 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 ⅓″ to ⅔″ long and abruptly narrowed below the middle to an linear to oblong tip, and are taller than the gynostegium. Collectively, the hoods are in the shape of a 5-pointed star. They are white or the same color as the petals but much paler. The horns are shorter than the hoods. They project from the hoods and are curved inwards. There is little or no fragrance.

The fruit is a narrow, spindle-shaped pod. It is 3″ to 4″ long and ¼″ to ⅓″ wide. It is held erect or ascending on an erect stalk. It opens on one side exposing the seeds to spreading by the wind. The seeds have a tuft of hairs at the tip that are whitish and about 1⅛″ long.

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

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