Swamp Milkweed is a wildlife-friendly perennial. Clusters of fragrant, pink flowers bloom at the top of stems, July-August. The flowers are followed by elongated seed pods, which are used in dried flower arrangements. The flower nectar is an important food source for bees, butterflies, and hummingbirds; it has special value for native bees. Swamp Milkweed is a host plant for butterfly and moth larvae (caterpillars), including Monarch Butterfly (Danaus plexippus) and Queen (Danaus gilippus). Stems and leaves have a milky sap, which contains cardiac glycosides. When ingested by Monarch butterfly larvae feeding on the leaves, the cardiac glycosides make them (and the adult butterflies) toxic to birds and other predators. As its name suggests, Swamp Milkweed prefers wet soils, but it will tolerate well-drained soils in cultivation. Its deep tap root makes it difficult to transplant once established. Use this plant in rain gardens, along edges of ponds or streams, and in other moist areas of the yard. It can also be used in the back of borders, in meadows, and butterfly gardens.