The Milkweed Seed

Forrest M. Mims III

Look carefully in fields and open areas along rural roads, and you may tiny patches of bright white. If there is no snow on the ground, stop for a closer look. You may find open pods of milkweed plants.

Each pod will be surrounded by a cloud of snow white parachutes the size of your thumbnail. At the center of each parachute will be a thin, dark brown seed about the size of this letter "O." The slightest puff of breeze will launch some of the parachutes into flight. They may carry their cargo hundreds or even thousands of meters away from the parent plant.

Inside the opened pod, more seeds are packed in neat rows awaiting their turn to take flight. As the pod opens more fully, these seeds will also take to the air.

There are some 2,500 species of milkweed around the world. About 100 are found in the United States.

Milkweed plants have a variety of uses. The silk from their seeds was once used to make candle wicks. During World War Two, children In the United States collected milkweed floss to stuff life vests for the military. Milkweed floss has also been used to stuff comforters, pillows and jackets.

Native Americans sought out milkweed plants, because their stems provide tough fibers for making cord and string. They may also have eaten various parts of non-bitter milkweeds. Even today some natural food enthusiasts prepare a variety of dishes from milkweed pods.

Milkweed plants are essential to the survival of monarch butterflies.

Female monarchs lay their eggs on milkweed leaves. But first they have to find a milkweed plant. Sensors in their antennae allow them to smell the presence of milkweed.

The real test occurs when the monarch lands on a milkweed leaf. She pokes thin spikes on her front legs into the leaf. Sensitive organs on her feet then tastes the fluid that emerges. If it tastes like milkweed, she prepares to lay an egg.

But first she looks around to be sure her egg will be the first to be laid on the leaf. If another female arrived first, its caterpillar might eat late arriving eggs while chewing on the milkweed.

The monarch caterpillar dines on the leaves until it is full grown. It then forms a transparent chrysalis and transforms itself into the adult butterfly.

The white sap of the milkweed is toxic to many animals. Because both the monarch caterpillar and adult contain traces of the poison in their bodies, it is thought by scientists that this protects them from predators.

Forrest M. Mims III and his science are featured online at www.forrestmims.org.

This feature was originally published in Forrest Mims's weekly science column in the Seguin Gazette-Enterprise, Seguin, Texas. The column is written for a general audience.