Asclepias tuberosa ssp. interior

Native

Dry to moderate moisture. Prairies, upland woods. Full sun.

July to September

Pale orange to dark reddish orange

12″ to 36″

This is a 12″ to 36″ tall, weakly erect, perennial herb. A single stem rises from a large, deep, thick, knobby, woody taproot. As the plant matures, it sends up multiple lateral stems from the taproot (tillers). Mature plants, with many flowering branches and multiple lateral tillers, appear bushy, round in form. The leaves and stems contain a watery, not milky, juice.

The stems are erect or ascending, stout, leafy, and densely covered with long, soft hairs. They are unbranched below and often form multiple branches near the top.

The leaves are alternate except just below the inflorescence, where they are opposite. They are numerous and crowded. They are 2″ to 4″ long, ¼″ to 1″ wide, narrowly lance-shaped, widest below the middle, and tapering gradually to the tip. They are attached to the stem on short, less that ⅛″ long, leaf stalks. The margins are untoothed and may be slightly rolled under. The upper surface is shiny and slightly hairy. The lower surface is more hairy and a lighter shade of green.

The inflorescence is 1 to several erect, umbrella-shaped clusters (umbels) at the end of the stem and rising from the upper leaf axils. The clusters are spherical, 2″ to 4″ in diameter, and are on a short stalk or no stalk at all. They typically have 6 to 25 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. They are ⅜″ to ⅔″ tall and are attached on flower stalks that are up to ¾″ long. The petals are pale orange to dark reddish orange. They bend backward at the base, hang downward, then curl upward near the tip. They are separated from the hoods by a distinct column. The hoods are the same color as the petals. The horns are shorter than the hoods. They project from the hoods and are curved inwards. The flowers are long-lasting and not fragrant.

The fruit is a narrow, spindle-shaped pod. It is 3″ to 5″ long and ½″ to ¾″ wide. It is held erect on a downward-curved stalk. It opens on one side exposing the seeds to spreading by the wind. The seeds have a tuft of white hairs at the tip.

This is the only milkweed in Minnesota with orange flowers.

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

Butterfly weed is a milkweed. Milkweeds are the only plants that Monarchs lay their eggs on. The eggs are laid on the underside of healthy young leaves.