Asclepias verticillata aka Eastern Whorled Milkweed

Asclepias verticillata has the common name whorled milkweed. This wildflower lives for years and belongs to the dogbane family. It grows wild in central and eastern Canada. Its native range also spans much of the United States. It grows in prairies, glades, and open woods. It also grows on ridges, streambanks, and in wet meadows. Garden plants reach 1–2.5 feet [0.30–0.76 metres] tall. They spread 1–2 feet [0.30–0.61 metres] wide. Chicago Botanic Garden gives a height of about 1.5 feet [0.46 metres].

The stems grow upright, with few branches. The plant spreads through rhizomes, which are underground stems. Short hairs cover its green stems. Broken stems and leaves give off white, milky sap. The thin leaves give the plant a fine texture. Three to six leaves form a whorl at each node. These rings grow at points along the stem. Each leaf joins the stem with no stalk. The leaf edges curl down. Short hairs cover the pale backs of the leaves.

Small white or greenish-white flowers grow in groups near stem tips. Groups also grow where upper leaves join the stems. Each flower has five petals and a crown-like center. Small hoods and curved horns form this shape. Missouri Botanical Garden lists bloom from June through September. North Carolina State Extension reports blooms as early as May. Chicago gives a shorter span, from July through August. Thin, smooth seedpods grow after the blooms and point upward. They split in fall, freeing seeds with white hairs. Wind blows the seeds away from the plant.

Full sun gives the best bloom. The plants can also grow in some shade. They grow in dry to moist soil that drains well. Sandy loam suits them well, but clay works too. Once settled in, plants cope with drought. Deer tend to leave them alone. Sources list USDA hardiness zones 4–9. Seeds grow with ease, and plants need little care. Rhizomes and new plants from seed can crowd small gardens. Remove pods before they split to limit new plants from seed. This milkweed suits borders, meadows, and native plant beds. It also suits butterfly gardens. The pods work in dried flower displays.

Bees and butterflies visit the blooms. Monarch larvae eat the leaves. North Carolina State Extension warns that the nectar is toxic to honeybees. Serious diseases are not a usual concern. Aphids may cause trouble. Milkweed bugs can harm pods. Aphid control can harm monarch larvae and other useful insects too. The plant is toxic to people, pets, and livestock. Eating large amounts can cause vomiting and diarrhea. It can also cause weakness and confusion. The sap can irritate skin and eyes.