Ohio Perennial and Biennial Weed Guide

Family:

Milkweed Family (Asclepiadaceae)

Other Names:

flesh-colored milkweed, rabbit milk, rose milkweed, rose silkweed, silkplant, swamp silkweed, water nerve root, white Indian hemp.

Origin and Distribution:

Swamp milkweed is a native of North America. It is currently distributed throughout Ohio in marshes, swamps, fens, ditches, open woods, wet prairies, fields, thickets, and shores. Swamp milkweed prefers moist sites.

Plant Description:

Swamp milkweed is a slender perennial. Its stems and leaves exude a white milky sap if cut or broken, which is a common characteristic of species in the Milkweed Family. It can be distinguished from other milkweeds by its habitat, as it is the only native milkweed species preferring wet ground. Reproduction is by way of seeds and weakly creeping roots.

• Root System:

  Roots about 1 inch in diameter, knotty, and surrounded by rootlets and creeping roots.

• Seedlings and Shoots:

  Stems of young plants are purple-tinged and their leaves have short hairs around the edges and on the prominent midveins located on the lower surface.

• Stems:

  Stems emerge either alone or in clusters from a single root crown. Stems are generally upright, 1 to 4 feet tall, hairy, leafy, undivided at the base, and branched at the top.

• Leaves:

  Leaves are opposite (2 leaves per node), 2 to 8 inches long, no more than 1 1/2 inches wide, numerous, and lance-shaped. Upper and lower leaf surfaces are usually hairless. Veins are clearly visible on the lower surface of the leaf.

• Flowers:

  Flowers consist of 5, downward-pointing petals and a 5-part central crown that are dull pink to deep pinkish-purple. Flowers are 1/4 inch wide. They form small clusters of between 10 to 20 flowers.

• Fruits and Seeds:

  Seed pods are 2 to 4 inches long, slim, rusty-green, and have elongated tips. Pods split lengthwise when mature releasing numerous flat, oval seeds. The brown seeds are 3/8 inch long and have winged margins and long, silky tufts of white hair at the tip.

Similar Species:

Swamp milkweed is similar in appearance to other milkweed species (Asclepias spp.) except its leaves, flowers, and seed pods are more slender. Also, the sap of this wetland milkweed is less milky than that of other species in the family.

Biology:

Swamp milkweed flowers from July through August. The plant is often found growing in several inches of water.

Toxicity:

This species is poisonous to livestock and small children if ingested in sufficient quantities.

Facts and Folklore:

• 'Incarnata' was likely included in the name because it means flesh-colored or flushed with pink, which describes the color of swamp milkweed flowers.

• Pueblo Indians harvested fibers from this plant that they used to make fishing line and sewing thread.

• Roots of swamp milkweed were used in the treatment of various ailments.