Asclepias viridis aka Antelope Horns

Asclepias viridis belongs to the dogbane family and lives for years. It has three common names: green milkweed, green antelopehorn, and spider milkweed. It comes from the central and east-central United States. Its range runs from Ohio and Nebraska to Florida and Texas. It grows in prairies, dry woods, fields, and roadsides. Garden plants stand about 1.5–2.5 feet [0.46–0.76 metres] tall. They spread about 1–2 feet [0.30–0.61 metres] wide.

Several green to purple stems rise from the base. Most stand upright, though some may lean along the ground. Fine hairs may grow near their tips. The simple leaves have smooth edges and pale veins. They range from oval to lanceolate, or lance-shaped. Most leaves grow in an alternate pattern, one after another. Some sit almost opposite each other on the stem. Their lower sides are paler than their upper sides. Cut or bruised leaves and stems give off milky sap.

Green flowers grow in groups called umbels at stem tips and leaf joints. Five upright corolla lobes, or petal sections, ring purple hoods. The flowers have no horns. Most bloom from May through July. Chicago Botanic Garden also notes blooms into August. Upright seed pods, called follicles, follow in summer and fall. These pods reach about 0.25–0.5 feet [0.08–0.15 metres] long. They split to free brown seeds with white, silky tufts. Wind blows the seeds away from the parent plant.

Give this milkweed full sun and soil that drains well. It prefers neutral soil with dry to moderate moisture. Once plants take root, they cope with drought and several soil types. Most sources place it in USDA zones 5–9. NC State extends that range to zone 4. It needs little care and grows well from seed. Treat seeds with cold before spring sowing to help prepare them. Long rhizomes, or underground stems, make plants hard to move. Plants spread through these stems and by seeding themselves. They do not count as invasive plants.

Use it in meadows, prairie plantings, and butterfly gardens. Borders suit it where nearby plants leave room to grow. Bees and butterflies feed on nectar from the flowers. Monarch caterpillars eat the plant, and deer tend to avoid it. Serious diseases are not a usual concern. Aphids may cause problems, and milkweed bugs can harm pods. Steps to curb aphids may harm monarch larvae and helpful insects. The plant has cardiac glycosides, which poison people and pets. Eating large amounts can cause gut upset, weakness, and confusion. Its sap can irritate skin and eyes.