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Aquatic and Wetland Vascular Plants of the Northern Great Plains

37. Asclepiadaceae, the Milkweed Family

1. Asclepias L. -- Milkweed

1. Asclepias incarnata L. -- Swamp milkweed

Tall, stout, milky-juiced perennial 6-15 dm tall, from a thick rootstock, glabrous except for short, appressed or curved pubescence in the uppermost part. Leaves simple, opposite, short-petioled, the blades linear-lanceolate to lanceolate or seldom ovate-lanceolate, 6-15 cm long, 1-5 cm wide, acute-tipped, entire, cuneate to rounded at the base. Flowers usually numerous in terminal and axillary umbels, deep pink to purplish-red, perfect, regular, 5-merous, 4-6 mm wide; calyx spreading to eventually reflexed, the sepals 1.5-2.5 mm long, often hidden beneath the reflexed petals which are 3-6 mm long; corolla with a petaloid corona above the petals, the corona comprised of 5 hoods which are 2-3 mm long, each with a subulate, incurved horn projecting from the orifice; stamens 5, the anthers united around the gynoecium, adherent to the stigma to form a structure called the gynostegium, the pollen of each anther sac contained in a waxy mass termed the pollinium, the pollinium of each anther sac connected to the pollinium in the sac of the adjacent anther by a translator, these double pollinia released intact at pollination; carpels 2, enclosed by the gynostegium, the ovaries separate but the styles and stigmas fused. Fruit produced by only a few of the flowers, usually 1 of the 2 carpels maturing, the fruit a large fusiform follicle containing many seeds which bear a fluffy white coma. Jul--Aug. Swamps, marshes, ditches, stream banks, springs and fens, where water is fairly fresh; frequent in e and c ND, e and s SD and most of NE; (N.S. to Sask., s to FL, TX and NM).
Asclepias incarnata
GIF- Distribution Map

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