Asclepias spp., including A. tuberosa L. (butterfly milkweed) and A. incarnata L. (swamp milkweed)
Milkweeds attract adult butterflies to the garden and provide the only rearing site for monarchs. Although the plants can be quite leggy, the unusual flowers are striking, and, of course, the seed pods are attractive and fun to play with because of the silky hairs attached to the seeds. The most common Wyoming milkweed is A. speciosa Torrey, common along roadsides, but it’s not the most attractive one. Butterfly milkweed (usually orange) is the most readily available species, but it seems to be at the edge of its range of survival in higher-elevation parts of Wyoming. Pink-flowered swamp milkweed, one of 14 milkweeds native to Wyoming, is becoming more popular. Milkweeds are easily grown from seed but require stratification.
Width: individual plants are only 6-8” wide but can form diffuse clumps
Water needs: moderate to low, once established
Exposure: full sun
Availability in nurseries: common to rare, depending on species (see above)
Native range: A. tuberosa, most of North America except for WY and to the north and west of WY; A. incarnata, most of North America except the West Coast and western Canada (WY native)
Plant family: Asclepiadaceae (often included in Apocynaceae)