Milkweed on the Move

The milkweed pods on the green milkweed, Asclepias virids, in my pasture are splitting open to allow the seeds inside a chance to catch a puff of wind and ride to a new location in hopes of establishing a new plant. This past weekend I watched as the silky puffball of threads attached to each seed were pushed this way and that by the wind. Occasionally one would let loose and a seed would begin its journey from the mother plant to a bit of earth to nestle into.

Another common name for this green milkweed is green antelopehorn. The problem with common names becomes clear when you try to figure out what type of milkweed a given plant is. There are several with common names of green milkweed or antelope horns. What they all have in common is that Monarch butterflies search them out as the host plant for their progeny. When Monarch larvae eat milkweed they

sequester toxic cardenolides in their bodies. This makes monarch larvae and the adult butterflies they turn into taste bitter and develop a level of toxicity for potential predators. Monarchs' bright orange coloration is thought to warn off predators from eating them and taking on the ill effects of this toxicity. It is thought that other species of butterflies mimic this coloration to trick predators into thinking they are toxic too.

However, there is a delicate balance that must be met in order to survive growing up on such a toxic diet. The toxins are produced by the plant as a defense and the Monarch larvae must avoid the sticky latex sap containing the toxins that is exuded when a milkweed plant is chomped on as well as not ingesting too much cardenolide. I came across a very interesting article describing this delicate balance that you might want to read too.