Asclepias
milkweed
4 species
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Asclepias cryptocerasHumboldt milkweed, pallid milkweed
Distribution: Occurring east of the Cascades crest in southeastern Washington; southeastern Washington to California, east to Idaho, Wyoming, and Colorado.
Habitat: Gravelly to heavy clay soil in the foothills and lower mountains.
Origin: Native
Flowers: April-June
Growth Duration: Perennial
Asclepias fascicularisMexican whorled milkweed, narrow-leaf milkweed
Distribution: Occurring east of the Cascades crest in Washington; northeastern Washington to Baja California, Mexico, east to Idaho, Utah, and Arizona.
Habitat: Sagebrush desert, usually along vernal stream beds.
Origin: Native
Flowers: June-August
Growth Duration: Perennial
Asclepias incarnataswamp milkweed
Distribution: Known from Okanogan County in Washington; Washington, also in Idaho, east across North America to Atlantic Coast.
Habitat: Riparian zone, including standing water
Origin: Introduced?
Flowers: August
Growth Duration: Perennial
Asclepias speciosashowy milkweed
Distribution: Occurring east of the Cascades crest and in the Columbia River Gorge in Washington; British Columbia to Mexico, east to the Great Plains and Great Lakes region.
Habitat: Riparian corridors, irrigation ditches, roadsides, and other at least seasonally wet areas at low elevations, often in loam soils.
Origin: Native
Flowers: June-August
Growth Duration: Perennial