Butterfly weed (milkweed)

Asclepias tuberosa · Apocynaceae

Native monarch host plant, widely promoted for pollinator gardens

Photo: Ragesoss, CC BY-SA 3.0, via Wikimedia Commons

Sun: Full sun
Soil: Well-drained, dry, sandy soil; tolerates poor soil
Soil pH: Not critical: grows in almost any well-drained soil and prefers sandy or poor soil
Water: Low. Long taproot; drought-tolerant
Hardiness: USDA zones 3-9 (some say 4-9)
Height and spread: 1-2 ft x 1-1.5 ft

Guv's tipButterfly weed is slow to emerge in spring, so mark the spot. Its deep taproot resents transplanting, and do tolerate those monarch caterpillars.

Through the year

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Sow or plant

In flower

Months are a rough guide. Time it by your own frost dates.

When to plant

Sow seed outdoors in fall (for natural cold treatment), or cold-stratify and sow in spring. Plant young plants or divisions in spring or by late fall. Slow to emerge in spring, so mark the spot. The deep taproot resents transplanting

Flowering

Spring to summer, mainly Jun-Sep

Pruning

Minimal. Leave old stems until spring (it emerges late). Deadhead if you like for a second flush. Remove pods before they split to limit self-seeding. Tolerate monarch caterpillar feeding

Making more plants

Seed (needs cold stratification) or root/rhizome cuttings. Difficult to transplant

Watch out for

Pest

Aphids (often yellow oleander aphid)

Look for: Aphids clustered on stem tips

What to do: Tolerate small numbers (lady beetles eat them); knock off with strong water spray every 2-3 days; insecticidal soap if heavy; avoid insecticides that harm monarchs

Disease

Crown/root rot

Rot of the crown or taproot in wet soil

Look for: Decline and rot in wet, poorly drained or soggy soil

What to do: Sharp drainage; use A. incarnata for wet sites

Always read and follow the label on any treatment, and check it is approved for use where you live.

Safety and spread

Pets and people: Toxic to dogs, cats and horses. Cardenolides (cardiac glycosides) cause vomiting, depression, weakness and possible seizures (ASPCA, milkweed). NC State Extension rates it low severity; the sap causes dermatitis. The University of California lists it as minor toxicity and a skin irritant

Weed risk: Not on the federal noxious weed list. Native to the eastern and southern US. Avoid non-native tropical milkweed (A. curassavica)

Checked against two or more reputable gardening sources. How we check our facts

Keep it by the back door

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