I first wrote about swamp milkweeds (Asclepias incarnata, Asclepiadaceae) a couple of months ago when they were flowering. Since that time these plants have endured attacks from insects (2, 3, 4, 5, 6) that are adapted to feed on their toxic cardiac glycosides. Although the insects benefit from the food source, the milkweeds can also benefit from insect pollination. While sap-feeding true bugs (order Hemiptera) and leaf-feeding beetles (order Coleoptera) only contribute to pollination to a small degree, nectar-feeding bees and wasps (order Hymenoptera) and butterflies and moths (order Lepidoptera) are much more important pollinators (Ivey, Martinez, and Wyatt 2003).
Now that we’re into autumn, the flowers have been pollinated and fertilized and they’ve developed into terminal pods bursting with hairy and winged seeds.
As with other milkweeds, the feathery plumes and wide wings help the seeds disperse by wind over a large area. With swamp milkweeds growing in floodplains, these structures also help seed dispersal by water (Wilbur 1976).
Ivey, C.T., P. Martinez, and R. Wyatt. 2003. Variation in pollinator effectiveness in swamp milkweed, Asclepias incarnata (Apocynaceae). American Journal of Botany 90(2):214-225.
Wilbur, H.M. 1976. Life History Evolution in Seven Milkweeds of the Genus Asclepias. Journal of Ecology 64(1):223-240.