Milkweed (Asclepias syriaca) along the South branch of the Potomac. Last year we began culturing milkweed for schools with butterfly programs.Milkweed sap has toxins called cardiac glycosides. When the caterpillars of the Monarch butterfly (Danaus plexippus) and other milkweed butterflies (subfamily Danainae in the family Nymphalidae) ingest the leaves of milkweed, the glycosides make the caterpillar poisonous to some predators. Adult butterflies retain the glycosides.
This useful table was prepared by students in Fairfax County Public Schools:
