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Prairie milkweed produces one and a half to two inch balls of 30-100 greenish-white flowers in the axils of a few of the mid-stem and upper leaves; the flowers are supported on 1/2"-3/4" pedicels. Each flower is about 1/8" across and 1/4" long; the flowers are a variation on the typical (complex) milkweed morphology with 5 sepals, a 5-lobed corolla with 5 petals (often with purple blotches at their tips) that are reflected backwards to cover the top of the pedicel, 5 hoods without horns, and a short central column that rises above the hoods; there is a distinct gap between the bases of the petals and the crown. Seedpods are 4-5" long with a fat base (attached to the pedicel) tapering rapidly to a narrow tip. Prairie milkweed can be confused with whorled milkweed (Asclepias verticillata) — both occur in Jackson Park — but whorled milkweed has even narrower (grass-like) leaves than prairie milkweed, is a shorter plant, and has pure white flower that do bear horns.

Asclepias

Asclepias hirtella

prairie milkweed [Blooms: Jun-Aug]

The flowerheads of swamp milkweed are erect, ~3" across, with 10-40 flowers; flowers are 1/4" across and typical milkweed morphology with pink petals and whitish hoods, but color can vary from pink to magenta; the central column is cream-colored and visible below the base of the hoods. The petals are reflected backwards but are not tightly pressed against the stem; the horns arch up and over the central column and taper to a sharp point.

Asclepias

Asclepias incarnata

swamp milkweed [Blooms: Jul-Aug]

The height of the stem and the leaves of Sullivant's milkweed are similar to common milkweed. Each plant produces 1-3 (total) flower clusters from the stem apex and adjacent leaf axils; each cluster is 2-4" across and has ~15-25 flowers, each ~1/2" across. The flower petals are pink to rich purple, with white bases; the hoods are usually noticeably lighter. The horns are laterally compressed (sickle-shaped) and their tips clearly overlap over the column.

Asclepias

Asclepias sullivantii

Sullivant's milkweed [Blooms: Jul-Aug]

Common milkweed's flowers arise from leaf axils, are 2.5-5" wide, hemispherical, and covered with typical 1/2" wide milkweed flowers ranging from light pink to reddish-purple; the petals, reflexed back around the base of the flower are darker than the hoods.

Asclepias

Asclepias syriaca

common milkweed [Blooms: Jun-Aug]

Butterfly weed has clusters of 8-25 flowers, in various shades of orange with touches of yellow or red, that arise from the stems and leaf axils. Individual flowers have a typical milkweed morphology, with the petals reflexed backwards over the flower stalk and the complex corona protruding. The central column of the corona in A. tuberosa is always yellow regardless of the shade of the remainder of the flower. This is the only Illinois milkweed with orange flowers and has narrower leaves than all other local milkweeds except whorled milkweed (A. verticillata, which has white flowers).

Asclepias

Asclepias tuberosa

butterfly milkweed [Blooms: Jun-Sep]

Whorled milkweed's flowers are white, occurring in small (1-3") clusters that rise from leaf axils. Individual flowers are typical milkweeds (except for their color), 1/4" across; horns are sickle-shaped, petals are white or greenish-white. Once you recognize that this plant IS a milkweed, given its grass-like leaves in whorls, it is impossible to mistake it for any other local species.

Asclepias

Asclepias verticillata

whorled milkweed [Blooms: Jul-Sep]