Short Green Milkweed
Milkweed family (Asclepiadaceae)
Description: This native perennial plant is 1½–2' tall and unbranched. The central stem is light green and usually slightly pubescent, otherwise it is glabrous. The leaves are usually opposite and angle strongly upward from the stem, otherwise they are alternate. They are up to 5" long and 1¾" across, and are usually lanceolate with short petioles. Because this is a variable species, the leaves can assume other forms as well. A typical leaf has a prominent central vein and smooth margins that gently undulate up and down. It is often slightly pubescent, otherwise glabrous. A single umbel of flowers may appear from the axils of the upper pairs of leaves. A typical plant will have 1-3 umbels, with each umbel consisting of 15-30 flowers. Each umbel has a short stalk and hangs downward. Each flower is about 1/3" long, consisting of 5 upper hoods and 5 deflexed petals. The hoods are without horns, and the central reproductive column is very short or absent. Instead, there are masses of winged pollinia. The flowers are light green to green, becoming yellowish green or purplish green as they age. Their pedicels are about ½" long and hairy. The blooming period occurs during early summer and lasts about 3 weeks. If successful cross-pollination occurs, a flower will be replaced by a spindle-shaped follicle about 5" long and 1" across at its widest. The surface of a follicle is smooth, but usually slightly pubescent. This splits open along one side, and releases numerous seeds, each one with a large tuft of white hair. Seed distribution is by wind. The root system consists of a central taproot. This plant occurs as widely scattered individuals, and rarely forms colonies.
Cultivation: The preference is full sun and rather dry conditions. This plant will also tolerate partial sun and mesic conditions. If anything, poor sterile soil is preferred, containing gravelly or sandy material, as this reduces competition from taller, more aggressive plants. However, it will also grow quite well in rich loam. After it blooms and forms seedpods, this plant steadily deteriorates.
Range & Habitat: Short Green Milkweed is widely distributed in Illinois, but it is absent from some eastern and central counties. (see Distribution Map). In areas where it occurs, Short Green Milkweed is uncommon to occasional. Habitats include openings in upland forests that are rocky or sandy; mesic to dry black soil prairies, sand prairies, gravel prairies, and hill prairies; barrens, limestone glades, and sand dunes; and abandoned fields. This species of milkweed usually occurs in high quality habitats, rather than disturbed areas. It is easy to overlook, even when it is in bloom.
Faunal Associations: The nectar of the flowers attracts bumblebees and other long-tongued bees, which are the principle pollinators. Ants are also attracted to the nectar, but they are not effective pollinators. The foliage and other parts of the plant are consumed by the larvae of Danaus plexippes (Monarch Butterfly) and the usual assortment of milkweed insects (see Insect Table). Mammalian herbivores shun this plant because the white latex of the leaves is toxic and provides the foliage with a bitter taste. The white latex also clogs up the mouthparts of insects, reducing the number of species that can feed on this plant.
Photographic Location: The photograph was taken at the Paxton Cemetery Prairie in Ford County, Illinois. This plant was growing in a mesic black soil prairie.
Comments: This non-showy plant is unlikely to receive favor from the mass market in horticulture, but it is nonetheless quite interesting to examine. This milkweed species is rather variable across different localities; there is a variety with narrow leaves that occurs in sandy areas near Lake Michigan. Short Green Milkweed can be distinguished from most other species of milkweeds by its nodding umbels of green flowers. The rare Asclepias meadii (Mead's Milkweed) has this characteristic, but its flowers are noticeably larger in size, and the hoods of its flowers have horns. Another milkweed species, Asclepias hirtella (Tall Green Milkweed) produces nodding umbels of flowers, but they are usually more white than green in appearance, and its leaves are more linear and narrow than the leaves of Short Green Milkweed.