Showy Milkweed

Growing Showy Milkweed

The keystone monarch host from the Plains to the Pacific. Spreads by rhizome in good soil; stays tighter where it's dry.

Where it belongs

Showy milkweed runs from the Great Plains west across the Rockies, the Great Basin, the Southwest, California, and the Pacific Northwest. It grows in open ground: roadsides, fence lines, old fields, and the edges of irrigation ditches.

This is the plant to reach for west of about the 100th meridian. Common milkweed and swamp milkweed are eastern species, and planting them in dry western gardens is a common way to waste three years finding out. Showy milkweed is the regionally correct answer, and it is a monarch host across the whole western migration.

Growing it

Full sun, dry to medium moisture, in loam, clay, or sand, hardy from zone 3 to zone 9. Two to four feet tall.

The leaves are the tell: thick, broad, and covered in fine gray felt, which is what lets it hold water in country where the air pulls it back out. The flower umbels are noticeably larger and more starlike than an eastern milkweed's, opening pink in June and July.

It does spread by rhizome in soil that suits it. In good moist ground it will form a colony, which may be exactly what you want in a meadow and a nuisance in a small bed. On dry ground it stays much tighter. If you want it contained, site it somewhere lean rather than fighting it in rich soil.

Start from seed with cold-moist stratification, or set out plants in fall. Like most milkweeds it puts its first year into root rather than top growth.

What it feeds

Monarchs lay on it throughout the West, and in much of that range there is simply no abundant alternative. Western monarch numbers have fallen sharply, and habitat plantings are one of the responses being pursued.

One regional caution worth knowing: near overwintering sites on the California coast, planting milkweed at all is discouraged, because it can interrupt the overwintering behavior. Inland, and away from the coast, the guidance is the opposite. Check with a local group before planting milkweed within a few miles of the coast in California.

The flowers also carry heavy scent and feed bees and butterflies broadly, quite apart from the host-plant role.

Living with it

The sap is toxic to livestock in quantity, which matters if you garden next to pasture. Wash hands after handling.

Leave the pods to open on their own. The silk carries seed on the wind, so remove pods before splitting if you want to limit volunteers.

Sources: USDA PLANTS Database (native range); Xerces Society (western monarch conservation and milkweed regional guidance); Lady Bird Johnson Wildflower Center, University of Texas at Austin (species profile).

It’s drought-tolerant, fragrant, and easy to grow.

Where it grows

Showy Milkweed is native to the Great Plains. In the wild you’ll find it across Arizona · Arkansas · California · Colorado · Idaho · Illinois · Iowa · Kansas · Minnesota · Missouri and 12 more states. Always confirm it suits your specific county with your state native plant society before planting.

Regional Garden has written state guides covering Showy Milkweed in 22 of them so far.

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