Butterfly Milkweed

Asclepias tuberosa

Apocynaceae

• Full Sun
• Size: 1'-2.5' tall x 1'-2' wide
• Drought Tolerant: Yes
• Evergreen: no
• Flower Color: Vivid orange to yellow-orange (June–August)
• Critical nectar source for hummingbirds, bumblebees, native bees, swallowtails, fritillaries, and skippers

Asclepias tuberosa — butterfly weed or orange milkweed — is a tuberous-rooted native perennial of eastern and central North American prairies, dry open woodlands, glades, and roadsides. While not native to Washington State, it performs with distinction in Spokane's semi-arid climate, where its deep taproot, drought tolerance, and love of full sun and well-drained soil align perfectly with local conditions. The specific epithet tuberosa refers to the tuberous, thickened root system that allows established plants to survive extreme drought and cold. This same taproot makes transplanting difficult; siting carefully at the outset and allowing the plant to establish undisturbed for two to three seasons produces the most rewarding results. Butterfly weed is distinct among milkweeds in one notable way: its stems and leaves lack the characteristic milky white latex sap found in other Asclepias species. Plant in average to lean, gritty, well-drained soil; avoid clay or consistently moist conditions, which promote crown rot. Do not overwater. The plant is often late to emerge in spring — mark its location and resist the urge to assume it has not survived.

Butterfly weed is one of the most visually striking native wildflowers available for the sunny perennial garden. The flowers are extraordinary in their intricacy — each individual floret consists of five reflexed petals and a raised central corona of five hood-like structures, all engineered with precision to require visiting insects to perform specific movements to access the nectar. Massed in flat-topped umbels 2–3 inches across in vivid orange, the overall effect from early summer through August is an eye-catching display that is virtually unmatched for sustained, saturated warm color in a drought-tolerant perennial. The alternate, narrow, lance-shaped hairy leaves on upright to slightly reclining stems are attractive throughout the season. By late summer, slender, spindle-shaped seed pods (3–6 inches long) develop and split open in fall to release hundreds of seeds, each attached to a long silky floss that carries them on the wind. The pods are valued in dried floral arrangements. The clump expands slowly over years as the taproot deepens and the plant reaches full size of 2–2.5 feet tall, with some mature specimens producing 20 or more flowering stems simultaneously.

As a member of the milkweed genus, it serves as a larval host plant for the Monarch butterfly (Danaus plexippus) — whose populations have declined by an estimated 80–90% since the 1990s, largely due to habitat loss and reduction of milkweed across the continent. Monarch females lay eggs specifically on milkweed, and the caterpillars feed exclusively on milkweed foliage, which contains cardenolide compounds that make the caterpillars and resulting butterflies unpalatable to predators. While A. tuberosa is considered somewhat less preferred by Monarchs than the native western species (A. fascicularis and A. speciosa), it still supports Monarch reproduction and is an excellent companion to those regional natives. Its nectar-rich flowers attract an exceptional diversity of pollinators: hummingbirds, bumblebees, long-tongued native bees, swallowtails, fritillaries, checkerspots, skippers, and beetles all visit regularly. Medicinally, the root was used by many Indigenous peoples of eastern North America to treat lung inflammations — hence one common name, Pleurisy Root — and as a laxative and general tonic. The genus name Asclepias honors the Greek god Asklepios, god of medicine.

Butterfly weed is an indispensable plant for sunny pollinator gardens, xeriscape borders, dry slopes, meadow plantings, and rock gardens throughout the Spokane region. Its vivid orange summer color combines beautifully with cool-toned companions: Salvia nemorosa 'Caradonna,' Agastache foeniculum, Nepeta faassenii, and Echinacea purpurea all provide complementary blue-purple tones that make the orange pop. For a warm-toned native prairie combination, pair with Rudbeckia fulgida 'Goldsturm,' Gaillardia aristata, and Helianthella uniflora. For maximum Monarch butterfly support, plant A. tuberosa alongside the regional natives Asclepias fascicularis (Narrowleaf Milkweed) and Asclepias speciosa (Showy Milkweed), which are native to the Spokane area and provide milkweed resources across a longer season. Ornamental grasses such as Schizachyrium scoparium and Festuca idahoensis add textural contrast. Allow generous spacing — the mounded clump needs 18–24 inches of elbow room — and resist dividing or transplanting established plants, as the deep taproot resents disturbance.