Vascular Plants of North Carolina
Account for Common Milkweed - Asclepias syriaca   L.
Members of Apocynaceae:
Members of Asclepias with account distribution info or public map:
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Section 6 » Order Gentianales » Family Apocynaceae
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AuthorL.
DistributionEssentially throughout the Piedmont (but scarce to absent in the far southeastern counties); present over the northern and central Mountains, but sparingly in the southwestern counties. Found only at a few scattered places in the northern half of the Coastal Plain. However, the species seems to be expanding its range southward, and may well occur over nearly all of the Mountains and Piedmont by now.

This is a Northern species that ranges south to central NC, northern GA, and OK. Over its large range, it is found in nearly every county, indicating an abundant species.
AbundanceIncreasing in recent decades. Formerly considered "Infrequent" in the Piedmont (Blomquist and Oosting 1959), but now generally common in the Piedmont and the northern 2/3 of the Mountains. Rare in the southwestern Mountains and southeastern Piedmont. Very rare in the northern Coastal Plain, known south to Washington and Pitt counties, but likely to increase or spread in upcoming decades. Weakley (2018) says "This species is apparently expanding its range southward", with which the website editors agree.
HabitatThis is a species of full to partial sun, in old fields, weedy pastures, roadbanks, woodland borders, and other brushy places. It is usually found in mesic conditions, not in wetlands nor in overly dry or sandy soils.
See also Habitat Account for General Apocynaceous Forblands
PhenologyBlooms from late May into August, and fruits from July to September.
IdentificationThis is a quite robust milkweed, with a thick stem that often grows to 5' tall, rarely to 6' or more. It is unbranched, and the numerous pairs of opposite leaves are quite large, being elliptical, about 6-7" long and about 3" wide. The leaves are quite thick and white/tomentose below. The top portion of the plant is heavily laden with 2-6 dense flower clusters (umbels) that contain "uncountable" numbers of flowers is a baseball-sized "globe" about 2-3" across. The flowers are mostly rose-pink in color, and the umbels seem so heavy that they often droop to the side. The species occasionally hybridizes with Poke Milkweed (A. exaltata). On a rare occasion, the species could be confused with the scarce A. purpurascens, but that species has a shorter stem, normally grows in damp places, and in bloom has deeper rose-purple flowers. Common Milkweed is an old-field colonist in many parts of the state, and where found usually occurs in very dense stands of several square meters, to the exclusion of most other species. The flowers are heavily used for nectar by a great diversity of insects, and as a result, butterfliers are usually drawn to stands of blooming Common Milkweed.
Taxonomic CommentsNone. The scientific name means "Syrian", though Fernald (1950) states "early carried from e. Am. to s. Eu. and supposed by Linnaeus to have come from the Orient". As this is a species of old fields and other brushy places, it has been occasionally suggested whether this species is native at all to North America, though apparently it is not known to be native outside of North America.

Other Common Name(s)Essentially no others in frequent usage. Rarely used are Butterfly-flower, Silkweed, Silky Swallow-wort, and Virginia Silkweed.
State RankS5
Global RankG5
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