[Illustration: GREEN-FLOWERED MILKWEED]
Leaves usually opposite or whorled; sepals 5; petals 5, usually reflexed
and with a 5-lobed crown; stamens 5, the pollen united into 1 or 2 waxy
masses in each sac; carpels 2, free except for the united disk-like
stigma.
Green-Flowered Milkweed. Silkweed (_Asclepiodora decumbens_) is a
widespread plant from Arkansas to Utah and Northern Mexico. It is found
on the central and western plains, blooming in early spring and
sometimes again in the fall. The stout, leafy stems, topped by the
ball-shaped heads of flowers form conspicuous clumps about a foot high.
The flowers have a sweet nectar which draws many insect visitors. They
bloom in April and early May, and the large warty pods mature in a few
weeks. As the seeds bear a tuft of hairs at one end, they are easily
scattered by the wind and other agents. It is one of the first plants to
appear on burned-over areas.
The milkweeds get their name from the bitter milky sap. The flowers are
quite different from other flowers in that there is a crown between the
petals and the stamens. In many the pollen is borne in two pear-shaped
masses with a thread-like connection. In the green-flowered milkweed,
purple hoods are attached to the crown and hang over the pollen-sacs.
[Illustration: BUTTERFLY-WEED]
Butterfly-Weed. Pleurisy-Root (_Asclepias tuberosa_) is a well-known
plant in dry fields from Maine and Ontario to Northern Mexico. In Texas
it is found in the sandy areas of the eastern and central parts. It
blooms in the late spring and summer. Other common names include orange
milkweed, orange-root, Indian posy, and orange swallow-wort. The leaves
are poisonous to stock, but the honey is not considered poisonous. The
monarch butterfly is a voracious feeder on the plant. It was at one time
valued for its medicinal properties, but is now little used. Several
plants are known by the common name of “swallow-wort” and are so called
because they bloom in the spring when the swallows appear.
The leafy stems often grow one to two feet high. At the top of the stem
are several clusters of small orange-colored flowers. The petals hang
down when the pollen is ready to be shed. There is a crown of five
erect, orange-colored hoods around the flat stigma.