Narrowleaf milkweed, a California native, is sometimes called Mexican whorled milkweed. This plant is a nectar source and host plant for the beautiful monarch butterflies. Allow monarch caterpillars to devour the plants. Great for native gardens. Gardeners can plant directly in the ground in the fall or transplant in late winter in mild climates. In areas with cold winters, transplant in the spring when the threat of frost is gone.
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Seed pack contents: .25G Sows about 100′ Row
Botanical Name: Asclepias fascicularis
Planting by Zones
- Narrowleaf milkweed is a perennial flower native to parts of the western U.S. Plant seeds during the cool season of Zones 9 and 10. Flowers bloom from June to September, but may not bloom until the second year.
- Plant in the spring after the danger of frost is gone.
Planting Narrowleaf Milkweed Seeds
- Direct seed or transplant. About 25% of a narrow-leaf milkweed’s seeds are protected by the need for cold to break dormancy. Growers in mild climates might notice a lower seed germination rate. Cold treatment may improve seed germination rates.
- To direct sow, plant seeds in debris-free, well-worked soil that has been deeply watered. Cover with 1/4” of finely sifted soil.
- If you are planting seeds in starter pots, plant seeds into thoroughly moist high-quality seed starting soil. Place seeds on top of the soil and cover with 1/4” of finely sifted soil.
- Plant in a full sun location. Space plants 6-12” apart. Plants grow 2-3’ tall with a spread of about 1’ wide.
Growing Narrowleaf Milkweed
- Narrowleaf milkweed plants are drought-tolerant and require little care once they are established.
- Mulching heavily around your plants will help with weed suppression and moisture retention.
- Be sure to plant enough narrow-leaf milkweed to sustain the monarchs! Monarch butterflies lay eggs on the plant in early spring. Once hatched, the caterpillars consume huge portions of milkweed as they prepare for adulthood.
Growing Narrowleaf Milkweed in Containers
- Narrowleaf milkweed does best when planted in-ground. After dying back in winter, potted plants do not re-emerge in spring as do in-ground plants. Keep in mind containers will dry out faster because they have more surface area and less soil to hold onto moisture.
Harvesting Narrowleaf Milkweed Flowers
- Allow narrowleaf milkweed to stay in the garden! It is loved by butterflies, bees, and other pollinators. It is most commonly grown as a native host plant for monarch butterflies. Narrowleaf milkweed will naturally die back in the winter to re-emerge in spring.
Southern California Pro-tips
- Narrowleaf milkweed is native to the western U.S. states of CA, ID, NV, OR, UT, and WA, where it grows below 7,000 feet in sagebrush, chaparral, grasslands, and foothill woodland communities.
- Once established it is drought-tolerant and does well in most types of dry to moist soils, even clay. Narrowleaf milkweed will naturally die back in the winter to re-emerge in spring.
- Support the monarch population by planting large amounts of densely spaced plants throughout your property; the cover of leaves provides protection for young caterpillars to hide from predators while ensuring a robust food supply!
- Narrowleaf milkweed is a wonderful addition to pollinator gardens. We suggest planting with other native, drought-tolerant flowers like California Bluebell, Desert Bee Plant, Golden Yarrow, Blue Sage, and Scarlet Sage, or those found in our Southwest Wildflower and Butterfly Garden mixes.
Additional Learning Resources
- USDA Plant information for narrowleaf milkweed can be found here.
- New to starting crops from seeds? Please watch our Seed Starting Presentation to learn the basics!
- Learn about growing all our crops on our YouTube page!
- Having pest issues? Check out in-depth information on garden pests at the UC Integrated Pest Management site.