Asclepias hirtella (Prairie Milkweed)
|Also known as:||Tall Green Milkweed|
|Habitat:||sun; dry to average moisture, prairies, meadows, glades|
|Bloom season:||June - July|
|Plant height:||1 to 3 feet|
|Wetland Indicator Status:||none|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Flowers are in round clusters 2 to 3 inches across that arise from the leaf axils in the upper third of the plant, typically with multiple flowerless axils above; 30 to 100 flowers in a cluster. Individual flowers are about 1/3 inch long, greenish often tinged with purple. 5 petals pull back away from the 5-parted crown, the tips flaring out. A distinct gap is between the petals and crown. The center column rises above the 5 hoods in the crown; horns are absent. Flower stalks average 1 inch long and are densely hairy.
Leaves and stem:
Leaves are 3 to 6 inches long and up to ½ inch wide, folding up from the midrib, toothless, pointed at the tip with a short leaf stalk, angled up or out, alternately attached but closely spaced on the stem and may appear opposite. Texture is rough from short dense hairs. The main stem is also rough to the touch and green to purplish. Plants are unbranched but may produce mulitple stems.
All Asclepias were formerly in family Asclepiadaceae but have been reassigned to Apocynaceae (Dogbane). While the leaves of Prairie Milkweed resemble those of another green milkweed, Asclepias viridiflora, the flowers are different enough to avoid confusion, plus A. viridiflora is typically a shorter plant with less densely packed leaves. A. hirtella is a rarity in Minnesota, added to the Threatened Species list in 1984 and, according to the DNR, is found only in one location in Mower County. The final of the 13 native Minnesota milkweeds took several trips to our southern counties, having failed to locate it in years past and a near miss the first time around this 2010 season. Perhaps my favorite family of wildflowers, the often subtle to vividly different variations of flower color and structure of the milkweeds provide me with great fascination! Thank you DNR Natural Heritage Program for your counsultations!
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Photos by K. Chayka and Peter M. Dziuk taken in Mower County
Have you seen this plant in Minnesota, or have any other comments about it?