The distinctive seedpods of milkweeds (Asclepias spp) are produced in late summer. At first a fresh green, they have turned dry and brown by this time of year. The shape and size of the pods (follicles) vary according to species, but generally they’re oval, tapering to a point at the top. These pods are filled with flat brown seeds tipped with a wisp of white floss (coma), which helps the seed to travel on the wind, much like dandelion seeds. But wind dispersal isn’t their only strategy–research indicates that some species of milkweed are dispersed by water in places such as irrigation ditches, culverts and drainpipes. Animals also can move seeds long distances, as the silky comas can hitch a ride on a passing creature’s fur.
When the seed is ripe and ready to disperse, the floss expands, causing the pod to burst. Because of the ingenious arrangement of the comas, each tucked under its neighbor, the movement of the wind acts as a zipper, pulling up and releasing the entire cluster into the air. Then the seed is off––hopefully to find a congenial resting place for the winter.
Like a number of other native plants, most species of milkweed seeds need a period of cold temperatures, followed by the warm weather of spring, in order to germinate ( a process known as cold stratification). Thanks to Mother Nature’s clever planning, that’s just what is provided for these peripatetic seeds– no assistance needed!
