Asclepias incarnata
Asclepias incarnata, known as swamp milkweed, is a herbaceous perennial native to North America. It grows in wet, muddy soils and is grown in gardens to attract butterflies with its nectar. The sap is milky and contains toxins that deter many animals.
The plant reaches about 100–150 cm tall and forms clumps from white roots. Leaves are opposite, narrow and lance-shaped, 7.5–15 cm long and 1–4 cm wide. It blooms in mid- to late summer with small, fragrant pink to mauve flowers (sometimes white) in rounded clusters. After flowering, green pods about 12 cm long develop; when ripe they split open to release seeds attached to silky hairs that drift on the wind.
Swamp milkweed prefers rich, wet soil and full sun or partial shade. It grows along the margins of wetlands, lakes, ponds, and other damp areas. It is an important plant for monarch butterflies: they nectar on the flowers and lay eggs on the plant, and the caterpillars feed on the leaves.
It is widely grown in butterfly gardens and monarch waystations. Many seeds require a cold period to germinate. To protect seeds from rain and birds, cover lightly with fabric or a shallow mulch; thick mulch can slow germination. The plant is not shade-tolerant, spreads slowly by seed, and in gardens may live about 2–5 years, though some plants can live longer.
This page was last edited on 2 February 2026, at 10:50 (CET).