This perennial wildflower is 2-6' tall and usually unbranched. The
central stem is light green to purplish green, terete, and
glabrous. Opposite pairs of leaves about 3-8" long and 1-3" across
occur along this stem; they are lanceolate-elliptic to ovate and smooth
along their margins. Both the tips and bottoms of the leaves are
wedge-shaped, rather than rounded. The upper leaf surface is medium to
dark green and
glabrous, while the lower surface is pale to medium green and glabrous
(or nearly so). The leaves are widely spreading and remain more or less
the same size along the stem. The distinct petioles are ½-2" long and
light green. The foliage contains a milky latex.
The stem terminates in one or more umbels of flowers
spanning 2-4" across. The umbels are relatively open and the flowers
droop somewhat from their pedicels. Each flower is about ¼" across and
long, consisting of 5 petals that hang downward, 5 curved cylindrical
hoods that surround a central column, and the reproductive organs. The
insignificant sepals are hidden by the petals. Each hood has an exerted
horn. The flowers
are bicolored: the petals are green or pale purple, while the
hoods and column are white or light pink. The slender pedicels are 1-2"
long, light green, and either glabrous or minutely short-pubescent. The
blooming period occurs during the summer for about a month. Afterwards,
fertile flowers are replaced by erect seedpods (follicles) that are up
to 6" long and ¾" across; they are narrowly lanceoloid in shape. During
the fall, each seedpod splits open along one side to release its seeds.
The seeds have tufts of hair at their apices; they are distributed by
the wind. The root system consists of a taproot.
The preference is partial or dappled sunlight, mesic conditions, and a
rich loam or sandy loam with organic matter. The location
should be protected from prevailing winds.
Milkweed is widely distributed across Illinois, but it is relatively
uncommon. Illinois lies along the western range
limit of this species. Habitats consist of woodland openings, rich
mesic woodlands, sandy woodlands, upland rocky woodlands, wooded
slopes, areas along
paths in woodlands, and woodland borders. Poke Milkweed is found in
deciduous woodlands where oaks, maples, and similar trees are dominant.
The flowers of Poke Milkweed attract
butterflies, including the Monarch and Great Spangle Fritillary
butterflies. These insects suck nectar from the flowers. Other insects
feed on the foliage, flower tissues, seedpods, pith of the stems, or
plant juices. The following beetles have been found on Poke
(Dogbane Beetle) and Labidomera
(Swamp Milkweed Leaf Beetle). Other insects
that feed on
milkweeds (Asclepias spp.
include larvae of Tetraopes
(Milkweed Longhorn) and Tetraopes
(Red Milkweed Beetle),
larvae of Rhyssomatus
(Milkweed Stem Weevil), Lygaeus
(Small Milkweed Bug) and Oncopeltus fasciatus
Bug), Aphis asclepiadis
and other aphids, caterpillars of the moths
(Unexpected Cycnia) and Cycnia
Cycnia), and caterpillars of the butterfly Danaus plexippus
Mammalian herbivores usually avoid consumption of milkweeds because
their foliage contains toxic cardiac glycosides and it is
Along a path in a sandy woodland at the Indiana
Park in NW Indiana.
This is a tall-growing milkweed with unusual bicolored flowers. In
Illinois, only Swamp Milkweed (Asclepias
) and Common Milkweed
are as tall and their flowers are usually more unicolored.
In some areas of the United States, Poke Milkweed has been known to
hybridize with Common Milkweed, producing plants with intermediate
characteristics. So far, such hybrid plants have not been observed in
Illinois. The common name, Poke Milkweed, refers to a junior synonym of
this species, Asclepias
. This latter scientific name was
no doubt inspired by the superficial resemblance of this milkweed's
leaves to those of an unrelated species, Pokeweed (Phytolacca