Milkweed

Common Milkweed (Asclepias syriacea) is an easily recognizable plant with a range that encompasses virtually all of North America east of the Rocky Mountains. It is one of over 140 species of milkweed, the genus Asclepias. Its common name comes from the white fluid released when the plant is harmed, and the scientific name derives from the healing properties, both real and imagined, for which the widely-ranging plants are used (Asclepius is the Greek god of healing).

Milkweed is known primarily as the host plant of the Monarch Butterfly (Danaus plexippus) which becomes toxic to predators by eating milkweed as a caterpillar. This toxicity is advertised with bright colors.

While carefully examining milkweed plants for the caterpillars and eggs of Monarch Butterflies for a post I planned to write about their life cycle I kept finding other insects instead, making me wonder what it was about milkweed that made it so popular among the six-legged set.

Essentially, what I found out after much research is that there are three basic reasons why so many insects like milkweed. First, it has a huge range. The many varieties of milkweed are spread out from Canada to Central America (and some has spread to Europe). And while many insects specialize on a single species of milkweed, some, like the monarch, are milkweed generalists. Second, milkweed’s tendency to produce prodigious quantities of nectar attracts insects like birds attract me. Finally, the aforementioned transferability of milkweed’s toxicity makes it popular among species that seek this clever form of defense. In addition to monarchs, an entire genus of beetles, Tetraopes, or milkweed beetles, feed on milkweed fearlessly, their bright colors signaling that they are not to be eaten.

Interestingly, though milkweed attracts many species to feed on its abundant nectar, most are not good pollinators for the plant. This, according to Wikipedia, is because its pollen, instead of being individual grains, bunches together into pollinia (pollen sacs) that stick only to those insects whose feet slip into notches in the flowers (primarily wasp species serve the purpose).

The Hummingbird Clearwing (Hemaris thysbe), a type of sphinx moth pictured above feeding on milkweed nectar, though frequently seen engaging in this activity, is not a good pollinator of the plant. Neither is the honeybee, the ant, nor the Virginia Ctenucha pictured doing the same thing below.

Besides the pretty flowers, abundant nectar, and milky sap, milkweed has another trait that, while it doesn’t help attract insects, does help the budding naturalist identify it from midsummer on: it grows its seeds in readily identifiable pods. The pods later burst open, releasing seeds that catch the wind on silky filaments, allowing next year’s crop of this remarkable perennial to be even more widespread.

So go out and plant some milkweed. You will enjoy watching every stage of the plant’s life and you will be providing much-needed habitat and food to a wide variety of fascinating creatures, even snails!