Asclepias tuberosa
Brilliant orange-flowered perennial and critical Monarch butterfly host plant. Thrives in dry, well-drained soils and provides vibrant summer colour.
Bloom & Fruit
Clusters of brilliant orange to yellow-orange flowers in flat-topped umbels. Each cluster contains 10-20 individual flowers. Blooms from early summer into late summer. One of the showiest native perennials.
Growing Conditions
Garden Uses
- Pollinator HostAttracts bees, butterflies, and beneficial insects. Plant near vegetable gardens to boost pollination.
- Larval HostHost plant for butterfly and moth caterpillars. Essential for supporting complete insect life cycles.
Companion Planting
These species thrive in similar conditions and complement each other ecologically.
Where to Buy
Ecology
Native Habitats
Associated Fauna
Propagation
- Seed (cold-moist stratification 30 days)
- Root cuttings (difficult)
Details
Description
Asclepias tuberosa is one of Ontario's most striking native perennials, producing brilliant orange flower clusters from early to mid-summer. Unlike most milkweeds, it lacks milky sap in its stems and leaves. The common name "Pleurisy Root" comes from its historical medicinal use by Indigenous peoples and early settlers for respiratory ailments.
Plants emerge late in spring (often mid-May in southern Ontario) from a deep, woody taproot. Stems are hairy, erect, and branched near the top. Leaves are alternate, lance-shaped, and dark green. The root system can extend 60 cm or more into the soil, making established plants extremely drought-tolerant.
Growing Conditions
Requires full sun and well-drained soil. Thrives in sandy or gravelly soils and tolerates poor, nutrient-deficient conditions. Does not tolerate heavy clay, wet soils, or competition from taller vegetation. Excellent choice for rock gardens, dry slopes, and xeriscaping.
Deep taproot makes transplanting difficult once established. Best planted in its permanent location from plugs or direct-sown seed. Hardy Zone 3-9.
Phenology
Late to emerge in spring. Flowering spans June through August, peaking in July. Seed pods (follicles) develop through late summer and split open in September-October, releasing seeds attached to silky floss for wind dispersal. Foliage turns golden-yellow in fall.
Ecology
A critical Monarch butterfly host plant. Monarch caterpillars feed exclusively on Asclepias species. Also serves as a nectar source for a wide range of butterflies (Swallowtails, Fritillaries, Skippers), native bees, and hummingbirds. The copious nectar production supports bee and wasp diversity.
The plant contains cardiac glycosides (cardenolides) that make it toxic to most vertebrate herbivores. Deer and rabbits avoid it.
Propagation
Seeds require 30 days cold-moist stratification. Sow in fall or stratified in refrigerator. Young plants need careful watering until taproot establishes. Division is difficult due to the taproot and is not recommended. Root cuttings may be taken in late fall from mature plants but success rates are variable. First-year plants are small; flowering typically begins in year two or three.