Asclepias syriaca

Asclepias syriaca (also known as the common milkweed, butterfly flower, silkweed, silky swallow-wort, and Virginia silkweed) is a species of milkweed plant. It belongs in the subfamily Asclepiadoideae.  It is native to North America.  It blooms from June to August.  The flowers are green and purple.  This species is found in prairies, meadows, and fields.  Common Milkweed likes damp to dry soil and sunny or partly shaded places.  It is about 0.5 to 1.5 meters in height (1½-5 feet).William Cullina (2000). Wildflowers: A Guide to Growing and Propagating Native Flowers of North America. The New England Wildflower Society. 

References

Other websites

Asclepias syriaca at USDA PLANTS Database
Asclepias syriaca at Evergreen Native Plant Database

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