This section is from the book "Who's Who Among The Wild Flowers", by W. I. Beecroft. Also available from Amazon: A Field Guide to Edible Wild Plants.
Silkweed.
Asclepias syriaca. Milkweed Family. June - Aug.
A plant 3 - 5 feet high, found in fields, roadsides, waste places. Common. New Brunswick south to North Carolina and Kansas; also westward.
Variable in color, dull crimson-pink, lilac or yellowish; one or more thick clusters springing from the leaf angles. Seed pods large, filled with silky down and flat, overlapping seeds.
Opposite, broad oblong, toothless.

Common Milkweed.
A. purpurascens.
Similar in habit to the preceding. Found in woods, dry fields. New Hampshire to Ontario, Minnesota, Kansas, and southward.
Crimson or crimson-magenta, in terminal clusters.
Elliptical or egg-shaped, upper ones taper-pointed, minutely downy beneath.
 
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