If you like to watch monarch butterflies (Danaus plexippus) flutter around your garden, you’ll want to add milkweed to your landscaping.
Monarch butterflies cannot live without milkweed, and its loss would directly affect the butterfly’s annual migration. Monarchs lay eggs specifically on milkweed, the eggs hatch into caterpillars and the caterpillars eat the plant, which contains cardiac glycosides, making them toxic to most species of birds and mammals.
Milkweed comes from the genus Asclepias, which is derived from the name Asklepios, the Greek god of medicine and healing.
American Indians and settlers used the roots of this plant for treating respiratory and other ailments.
Asclepias consists of 130 herbaceous perennials species. Of these, 11 varieties are native or naturalized in Pennsylvania. The three most common species in this region are common milkweed (Asclepias syriaca), butterflyweed (Asclepias tuberosa), and swamp milkweed (Asclepias incarnata).
Common Milkweed (Asclepias syriaca)
Common milkweed is the most well-known species of milkweed native to North America. It thrives in full sun to partial shade and in average to well-drained soils and is commonly found in pastures, field edges and along roadsides. Spreading by underground rhizomes makes this plant a good choice for erosion control. Its height can range from 4 to 6 feet. It has a short bloom period, from June to August, when it contains large clusters of fragrant pink flowers in spherical umbels at the top of the plant and arching habit. It produces opposite pairs of ovate leaves up to 6 inches long, on a single stalk. Undersides of the leaves are covered with short wooly hairs.
Butterfly weed (Asclepias tuberosa)
Butterfly weed, or butterfly milkweed, favors full sun in dry to medium soil. It is a hardy, drought-tolerant species reaching 1 to 3 feet in height and should be spaced 1 to 3 feet apart. The bloom period can range from late summer to fall. The vibrant orange to slightly yellow flowers are an easy way to identify it. Unlike the majority of milkweeds, the sap of this variety is not milky. It blends well in a perennial garden because of its clump-forming habit and height. Remove seed heads in the fall to further reduce its spread.
Swamp Milkweed (Asclepias incarnata)
As the name suggests, swamp milkweed does best in wet soil with full sun or partial shade. It can reach a height of 4 to 6 feet and should be spaced 2 to 3 feet apart. Leaves are smooth, narrow and lance-shaped with sharp tips and occur in pairs. Swamp milkweed has a long summer bloom period and flowers can range from mauve pink to purple. Five tiny, delicate petals are crowned with five nectar cups that are crucial in its intricate pollination. This species of milkweed is a great choice for wetland rehabilitation.
Many species of milkweed are quite easy to grow from seed. Head outside in the autumn, or even in the early winter, and sprinkle the seeds around the garden.
Burying the seeds can reduce germination rates since milkweed seeds need light to germinate. Just drop the seeds in the garden and press them down with your hand.
Once you’ve sprinkled the seeds over the soil, there’s nothing else to do but wait. In spring, they’ll germinate and begin to grow. If you want, once the seedlings are a few inches tall, you can dig them up and move them around in the garden.
Be sure the new plants stay well watered until they’re established. After that, milkweeds are hardy plants that will survive with very little care.