Asclepias syriaca aka Common Milkweed

Asclepias syriaca is also known as common milkweed. This wildflower lives for more than one year. It belongs to Apocynaceae, the dogbane family. Its native range covers central and eastern Canada and the United States. It grows in fields, thickets, and open woods. It also grows on roadside ground. Garden plants reach 3–5 feet [0.91–1.52 metres] tall. Some reach 6 feet [1.83 metres]. RHS reports shorter plants. Strong stems grow upright from long, spreading rhizomes. These stems grow below ground. They can form large groups of plants over time.

The broad, pale green leaves grow in opposite pairs. They have reddish veins and soft hairs beneath. Each leaf is oblong, with a thick, leathery feel. The plant sheds its leaves at the season’s end. Damaged leaves and stems give off white, milky sap. Scented flowers bloom from June through August. They form domed clusters called umbels. These grow beside the upper leaves and may droop. Flowers come in pink, mauve, lavender, and white. Each small flower has a crown-like part at its centre.

Gray, swollen seed pods follow the flowers in summer. They have rough, warty skins with fine hairs. Ripe pods split open and release many small seeds. Tufts of silky hair help wind carry the seeds away. Gardeners use the pods in dried flower displays. Bees and butterflies come to the flowers for nectar. The plant hosts the young, or larvae, of monarch butterflies. It also hosts the larvae of milkweed tussock moths. Native Americans used its stems for fibre. People have used seed floss for life jackets and bedding.

Grow common milkweed in full sun and soil that drains well. It copes with poor soil, dry ground, and drought. It grows in USDA hardiness zones 3–9. It needs little upkeep. Seeds and root cuttings make it easy to grow more. It suits meadows and butterfly gardens. It also suits large spaces where plants can spread and grow freely. Its fast spread makes it hard to keep in small borders. Plants also sow their own seeds. To stop this, remove pods before they open. RHS lists it as invasive in the UK. The UK bans its sale, and existing plants need control.

Serious pest and disease problems are rare, though aphids may gather. Creatures that prey on aphids can help keep them in check. Aphid control can also harm monarch caterpillars and other useful insects. PFAF records food uses for cooked buds, flowers, and young shoots. These records do not make the raw plant safe to eat. Several plant parts contain poisons that harm people and dogs. They also harm cats and horses. Eating enough can cause vomiting, weakness, and other illness. The sap can irritate skin and eyes. PFAF also records past uses as medicine. It warns of the plant’s toxic effects.