Wilderness Underfoot: Got milkweed?

StoryImage( ‘/Images/Story//Auto-img-115394503132390.jpg’, ”, ‘The common milkweed – Asclepias syriaca is native to most of eastern North America. About 100 milkweed species are found in the U.S., while most of the 2,400 species occurring worldwide are found in Africa and tropical Central and South America.’);
StoryImage( ‘/Images/Story//Auto-img-115394503932390.jpg’, ”, ”);

For at least two or three more weeks, you’ll be able to see milkweed flowers in bloom

With clusters of bright pink flowers atop distinctive broadly-leaved stalks, milkweeds can now be spotted blooming on the grassy edges of open country highways. Once pollinated, the flower clusters will be replaced with large green follicles—the pods in which the seeds are contained.

As the seed pods grow, milkweed plants often lose some of their older lower leaves. Nutrients and energy from these leaves are consumed by the plant, ensuring the youngest leaves survive to nourish the root system in preparation for the upcoming winter. This also enriches pods so they can produce seeds.

By the end of summer, the seed pods will be about 4 inches long. They’ll dry out and split open, and the fluffy white-haired seeds will be swept away by wind.

Although the milkweed is capable of reproducing by seed dispersal, this is really only a backup survival strategy. As with many prairie plants, the milkweed returns each spring thanks to root systems that store nourishment over winter and send out new shoots during the growing season. Most of the milkweed plants you see in any field are actually offshoots from fleshy rhizomous roots that have been well established for several years.

The milkweed is a plant that prefers rich loamy to sandy soils, with adequate moisture, and areas of bright sunlight. The common milkweed is somewhat more aggressive than the prairie milkweed when it comes to spreading out and claiming territory. In our region, you can see both plants, which are very similar in appearance and difficult for the amateur naturalist to distinguish.

Bees, wasps, flies and hummingbirds serve as milkweed pollinators. These creatures enjoy the nectar of milkweed flowers. The rest of the plant is avoided by most animals, however, with the exception of a few insects that have adapted to its bitter flavor and its milky sap, which often contains toxic compounds.

The most well-known insect that can feed on milkweed is the caterpillar of the monarch butterfly. Milkweed is this caterpillar’s sole source of food and shelter, on which the young monarch will metamorphize from larva to pupa to adult. The striking orange and black colors of the monarch butterfly—and the bold tiger-stripes of the caterpillar—are a warning to other animals that it tastes terrible. It acquires its bad taste from the bitter compounds of the plant itself.

The same bold color/bad taste strategy is employed by most of the insects that feed on the milkweed. If you have an opportunity to examine a milkweed up close, note the beetles and bugs that live on the plant. They’re typically very colorful.

From the July 26-Aug. 1, 2006, issue

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