Asclepias incarnata aka Swamp Milkweed

Asclepias incarnata, or swamp milkweed, belongs to the dogbane family. This perennial grows in central and eastern North America. Its range reaches from Canada through the United States into northern Mexico. Wild plants grow in swamps, wet thickets, and along shores. In gardens, it forms upright clumps of leafy stems. It loses its leaves at the end of the season.

Garden plants reach 3–5 feet [0.9–1.5 metres] tall. North Carolina State gives a spread of 2–3 feet [0.6–0.9 metres]. RHS lists a narrower spread, up to 1.6 feet [0.5 metres]. The stems are thick and carry narrow, green leaves. Leaves can reach about 0.5 feet [0.15 metres] long. Small, scented flowers form clusters near the stem tops. Their shades range from pink and purple-pink to white. July and August form the main bloom period. Some sources report flowers into early autumn. Narrow pods follow the flowers and change from green to brown. The pods split open and release seeds with silky tufts. Wind carries these seeds away from the parent plant.

Give swamp milkweed full sun and soil that stays moist. It can also grow with some shade. Fertile loam suits it, but it also tolerates clay. RHS lists sand and a broad range of soil pH. Wet ground suits this plant, including pond and stream edges. It can adapt to less wet sites with moist soil. Published US hardiness ranges differ, from zones 3–6 to 3–9. RHS gives it a UK hardiness rating of H4. It needs little upkeep and does not need pruning. Grow new plants from seed, division, or spring basal cuttings.

Use it in borders, meadows, and gardens for native plants. Low spots with damp soil also suit it. Its flowers supply nectar to butterflies and other pollinators. Monarch caterpillars feed on the plant, and deer tend to avoid it. Serious disease problems are rare, but aphids can cause trouble. Milkweed bugs can harm the seed pods. Aphid control may also harm monarch caterpillars and helpful insects.

RHS warns that eating this plant can cause harm. PFAF records cooked food uses for buds, shoots, and young pods. Those records do not establish that eating it is safe. PFAF also reports past root remedies, not proven treatments. Other recorded uses include stem fibre for cloth and twine. The silky seed hairs have served as stuffing material.