Asclepias viridiflora aka Green Antelopehorn Milkweed

Asclepias viridiflora has the common name green comet milkweed. This wildflower lives for many years. It belongs to the dogbane family. Its native range spans much of North America. It grows in southern Canada and the United States. Its range also reaches northern Mexico. Wild plants grow in prairies, dunes, grasslands, and open woods. They also grow at woodland edges and in limestone glades. The plant favors sites where the ground stays intact. It does not grow well on disturbed ground.

Garden plants reach 1–2 feet [0.3–0.61 metres] tall and wide. Each plant grows from a large central taproot. Plants tend to grow alone, not in colonies. Stems stand upright, have no branches, and bear short hairs. They range from pale green to purple-green. Hairy leaves grow in pairs, one on each stem side. Their upper sides are darker than their lower sides. Leaf edges may look folded or wavy. In dry soil, leaves grow longer and narrower. With more water, they grow wider and rounder. Both leaves and stems hold milky sap.

Small flowers form round, hanging clusters called umbels. These grow near the upper leaves. Each cluster holds about 15–45 flowers. Blooms are pale green or yellow-green. Some have a touch of pink. Plants bloom for about three weeks between May and August. Chicago Botanic Garden lists a July to August bloom season. Smooth pods with pointed tips form after the flowers. These pods, called follicles, reach about 0.33 feet [0.10 metres] long. They turn brown in fall and split along one side. Flat brown seeds have tufts of white hair. These tufts catch the wind. Plants lose some visual appeal as pods form.

Grow this milkweed in full sun, in soil that drains well. It also accepts part shade and poor soil. Sandy, loamy, and rocky soils suit it. Rich soil works too, if water drains well. Chicago and NC State favor dry soil for growing it. PFAF instead says it prefers moist, light, rich soil. Chicago lists USDA hardiness zones 3–9. PFAF notes that plants dislike harm to their roots. Place young plants where they can stay. Meadows, native gardens, and borders suit this plant.

Bumblebees pollinate the flowers. Monarch caterpillars feed on the plant. Mammals tend to leave it alone. NC State reports no major disease trouble. Aphids and several insects that feed on milkweed seldom cause much harm. Large and small milkweed bugs can cause severe pod damage. The sap may irritate skin and eyes. Eating quantities can cause gut upset, weakness, and confusion. PFAF lists dried root as a soup flavoring. Its wider food claims concern other milkweeds, not this species. PFAF also notes past use as medicine. That does not mean it is safe.