Butterfly Weed

Butterfly weed is a native perennial of eastern and southern North America, including Mexico. It forms upright clumps about 1 to 2 feet (30 to 61 cm) tall, though some guides give up to 3 feet (91 cm). Its flat-topped clusters of orange to yellow-orange flowers are a major nectar source for butterflies, hummingbirds and other pollinators, and it is a larval host plant for monarch caterpillars.

Unlike most milkweeds, it has clear sap rather than milky sap. It grows from a deep taproot, which makes it hard to move once it is planted.

Sowing. Start seed indoors about 8 to 10 weeks before the average last frost; one seed company suggests 7 to 9 weeks. Plant the seed ¼ inch (6 mm) deep in a seed-starting mix. Seeds sprout in 14 to 21 days at 65 to 70 °F (18 to 21 °C).

Transplanting. Move seedlings into larger cells or 3 to 4 inch pots 3 to 5 weeks after sowing, and don’t let them become pot bound. Harden them off and set them outdoors after the last frost.

Direct sowing. Seed can also be sown outdoors in fall after frost, or in fall or spring. Seed sown in fall goes through a cold period and emerges in spring. Some guides mention a cold, moist stratification before indoor sowing, while one seed company lists cold stratification only for pleurisy root, a name this plant also goes by.

Growing conditions. Give it full sun, though partial shade is also listed. It prefers dry to medium, well-drained soil and tolerates poor soils.

Patience. Plants are slow to establish and usually take two to three years to bloom from seed. Because of the deep taproot, plants don’t transplant well, so it is best to choose the final spot early.

Watering. Once established, plants are very drought tolerant. Make sure the soil drains well, since root rot can develop if it stays wet.

Pruning and mulch. Leaves turn dull yellow in fall, and it is best to wait until spring to cut back the stems. Avoid heavy winter mulch, which can cause crown rot.

Deadheading. Removing spent flowers may prompt a second flush of blooms about a month later. Mature plants can self-seed unless the seed pods are removed before they split.

Aphids. Aphids are a common pest and may cluster at the top of the plant. Knock them off with a strong spray of water every two or three days for a week. Small numbers of aphids are often eaten by beneficial insects.

Disease. Crown rot can occur in wet, poorly drained soil, and the plant can also get rust and leaf spot. Plants need well-drained, dry, coarse soil or they can succumb to diseases.

Rabbits and deer. Deer are not a problem for this plant. Some guides say rabbits leave it alone, while others say rabbits may damage it.

Flowers make an excellent cut flower. The spindle-shaped seed pods, which are 3 to 6 inches (7.5 to 15 cm) long, can be used in dried arrangements.

Wear gloves when handling this plant, because its clear sap can cause contact dermatitis and eye irritation. One profile says the plant is harmful if eaten. Another says eating large amounts can cause stomach upset, nausea, vomiting and weakness, and rates its poison severity as low. Don’t eat any part of the plant. The plant is listed as a problem for cats, dogs and horses, but the information used here doesn’t give a toxicity level for pets, so keep pets from chewing it.