Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: SUNDAY, August 15, 1993 TAG: 9309170409
SECTION: EXTRA PAGE: 3 EDITION: METRO
SOURCE: Patrica Held
DATELINE: LENGTH: Medium
The name milkweed comes from the fact that many of the species in this family produce a thick, milky liquid that flows from their stems and leaves. This sap contains a chemical that is closely related to digitalis.
The blossoms of common milkweed are flat with rounded clusters of pinkish-purple flowers. Once these blossoms are finished blooming, large puffy seed pods covered with wart-like bumps follow. Within these pods are silken seeds that explode in autumn and take to the air, spreading throughout a wide area.
This flower has one express purpose: to trick insects. The blossoms have a unique mechanism to ensure the act of cross fertilization, important for the continuation of the species.
The best way to understand this process is to watch it. Next time you are in a field with milkweed, take a moment to observe insects as they land on a blossom.
The flowerhead of milkweed comprises clumps of small cups filled with nectar. As an insect collects this nectar its foot slips between the cups. The pollen lies here in between. The only way this pollen can come into contact with the female flower is if it is pulled out and carried over. In order to release its foot the insect must jerk forcefully, pulling out the pollen too. Then it deposits the collected pollen as it flies from flower to flower, performing the task of cross pollination. Tiny insects that are too weak to pull their stuck feet from the trap remain there to die.
The most common insect visitor on the milkweed plant is the monarch butterfly. Its entire life cycle is associated with milkweed. The female lays a tiny speck of an egg on the undersurface of a leaf and in a few days hatches into a green caterpillar ringed with black, yellow and white. The larvae remain on the plants. Here they continue to feed on the leaves and mature. Still on the milkweed plant, the larvas eventually go into a pupal or cocoon stage. Finally, the adults emerge to reveal beautiful orange and black butterflies.
The monarchs' bright colors act as a warning to predators that this butterfly is not good to eat. Its bitter flavor is probably from the milkweed sap from the leaves, which it ate in its larval stage.
Other insects associated with milkweed are also orange in color and are equally bad-tasting. Look for the red and black long-horned beetle on milkweed's stems and roots, as well as giant lady bugs. Aphids, assassin bugs and crab spiders are also regular milkweed visitors.
In addition to common milkweed, which has the characteristic pinkish-purple flower clusters, another member of the milkweed family is butterfly weed. This plant has brilliant orange blossoms and is often found on patches of bare dry ground along roadsides or in fields. It grows in shrublike patches wherever the soil is at its worst. Its spectacular displays make it desirable as a garden plant. But it is very difficult to cultivate and almost always refuses thrive when it is planted. It is better left alone to choose where it wants to grow.
Milkweed likes deep, well-drained soil. They serve as indicators of the amount of boron, a mineral substance, in the soil. Milkweed grows yellow and deformed foliage when there are inadequate amounts of this substance present.
\ Patricia Held will respond to readers' questions on the plant and animal wildlife in the region. Mail inquiries to Patricia Held, P.O. Box 65, Goode, Va. 24556.
\ Patricia Held is a Bedford County free-lance writer and author specializing in natural history.
by CNB