Asclepias: Milkweed
There are over 200 species of Asclepias worldwide, and more than 70 of those native to North America; about a half-dozen can be found in parts of Oregon. It is highly useful as both a nectar plant for adult butterflies and as a food source for the growing caterpillars.
Plant care & info
Family: Asclepiadaceae
Genus: Asclepias
Common Name: Milkweed, Butterfly Weed
Mostly open, moist to dry, rocky areas, low to mid elevation, throughout the region.
Leaves opposite or whorled, on flowering stems 2-3 feet in height. Flowers are unusually formed clusters of five reflexed, fused petals and sepals that give them a star-like appearance. Color is a combination of white to pink to purple. Stems and leaves contain a milky sap. Caution: most species of this plant are poisonous to humans.
Milkweed thrives in full sun to light shade, and requires very well-drained soil. Grows and spreads by underground rhizomes.
Pests and diseases generally not a problem. Yellowing leaves is a sign of over-watering or insufficient drainage.
The chemical compounds in milkweed sap can cause dermatitis if it contacts the skin, and the plant is considered poisonous to humans.
Here is more information about Asclepias and its relationship with Monarch butterflies, as well as about the annual migration:
The milky substance in the stem and leaves of the plant that give it its common name contains a chemical compound that, when ingested by the caterpillar, acts as a repellant to predators. This is especially true for the Monarch butterfly and Asclepias speciosa, as it is the only food source for the Monarch caterpillars!
Every autumn millions of Monarch butterflies undertake a 3000-mile migration from Canada and northern United States south into far southern California and Mexico to spend the winter where temperatures are warmer and food sources abundant. Northwest writer Robert Pyle wrote a book about this amazing annual phenomena, called Chasing Monarchs.
As habitat in the wild is lost to development, maintaining compatible food and nectar supplies for butterflies becomes even more important.
Besides their usefulness as a butterfly plant, the milkweeds are also beautiful. Leaves are broad or thin, standing generally 2-3 feet tall (sometimes taller), with rounded clusters of tiny flowers that look like small stars, often in a mixture of creamy white and pink, sometimes deepening to a rich purple.
Asclepias requires excellent drainage and a mostly- to full-sun location; yellowing leaves indicate either too much water or poor drainage. Too much retained water can also result in root rot.
But in general, all species of butterfly weed are virtually pest and disease-free (if you notice the leaves on your plant are being eaten, you may have successfully attracted butterflies to your garden!).
Explore Native Milkweed
Showy Milkweed
Asclepias Speciosa: Showy Milkweed
Showy milkweed grows through the Willamette Valley and is the most commonly available Asclepias in nurseries. It also hosts Monarch butterflies at every stage of development! Pink flowers bloom from late spring to mid-summer. Blue-green lance-shape leaves are up to 6″ long and have a thin layer of white fuzz. Grows to 3′ x 3′, Sun, Hardy Z3.
Narrowleaf Milkweed
Asclepias Fascicularis: Narrowleaf Milkweed
Long, narrow leaves in whorls up the stems of this 2.5′ milkweed. Flowers are generally purplish-pink and white. It grows in dry to moist soil, near streams and at the coast — in sandy (fast-draining) soil.
Heartleaf Milkweed
Asclepias Cordifolia: Heartleaf Milkweed
Elongated heart-shaped leaves, purple flowers arranged in more open, drooping umbels. Found in the dry spots of southern Oregon and into California. Extremely drought-tolerant once established.
Swamp Milkweed
Asclepias Incarnata: Swamp Milkweed
An exception to the rule: This is an Asclepias that grows in wet conditions. Grows 3-4′ tall, narrow green leaves and clusters of bright pink flowers. Not native to Oregon (the farthest west it gets is Idaho), but if you have a wet garden, there is a butterfly weed for you too!
Find Natives for your garden
We offer a great selection of Northwest Natives from spring through fall. The plants featured are highlighted favorites, but they do not represent ALL of the plants we carry. For a more complete list, see our Northwest Native Plant List.
