Narrow-leaf milkweed (Asclepius fascicularis) is the native variety most commonly available currently in North San Diego. It was the primary type distributed in April to some 90 Solana Beach families by the City of Solana Beach’s Climate Action Commission and the SeaWeeders Garden Club.
Narrow-leaf milkweed naturally occurs on dry ground and sunny spots in valleys and foothills at elevations from 50 to 200 meters. Its range extends from Baja California through California to Washington. Once established, the plant self-propagates primarily through rhizomes. Learn more here.
Local growers are working to improve the availability of additional native milkweed varieties, which are best for our Western monarchs because they are the host plants the butterflies naturally seek while migrating each year here. Others include:
Asclepias Albicans - Whitestem Milkweed
Asclepias Californica - California Milkweed
Asclepias Eriocarpa - Indian/Woollypod Milkweed
Asclepias Erosa - Desert Milkweed
Asclepias Subulata - Rush Milkweed
Growing from seed, in plots or in pots
Sow seeds directly in the ground in Spring or Fall. Some growers recommend mixing the seeds with sand to make them easier to disperse. No need to sow deeply. According to the California Native Plant Society of San Diego, you can simply loosen your soil, scatter seed, and cover lightly. Milkweed and other nectar plants do best in relatively light, low-clay soils. Good drainage is needed to provide aeration and prevent root rot.
If you don’t have a plot, start your seeds in flats or small pots, using soil that provides for aeration. The California Native Plant Society of San Diego (CNPSSD) recommends a mix of 1/3 peat, 1/3 vermiculite and 1/3 pearlite. Or just add a topping of vermiculite to potting soil to help retain moisture. Plant about three seeds per container, just 1/4 inch deep.
Water regularly to keep the soil evenly moist every day. If we get hot dry spells, you may need to water twice daily because small containers dry out quickly. Creating a green-house environment with a plastic lid can help retain moisture.
Be patient. CNPSSD experts say it can take up to five weeks before sprouts emerge, although some of our SeaWeeders have seen shoots in as few as two weeks.
Whether seeding in ground or in containers, be sure to pick a spot that gets plenty of sun — at least six hours a day. When your seedlings have at least two sets of leaves and healthy roots, you can “pot up” to a larger container. When they look hardy enough to put in the ground, pick a spot near a fence, shrub or wall that can serve as a windbreak for butterflies and provide shelter for caterpillars to pupate. Potted plants often don’t come back in the following year. Revegetation is improved by planting in the ground.
For their first season, plants may remain small. Milkweed naturally dies back — goes dormant — in winter. To encourage regrowth, you can cut back bare stems.
Managing pests
You may find that aphids seem to like milkweed as much as the monarchs do. But don’t use pesticides on or around your plants; they are harmful to eggs and caterpillars as well as to beneficial insects and organisms. Aphids won’t hurt the caterpillars, but if they bother you, spray them off with water from a hose or sprayer bottle. Or, release lacewings or parasitic wasps in your butterfly patch.
Remember that your milkweed is food for monarch caterpillars! Don’t be startled if you find them chomping the plants to their nibs. The plants will come back, but the caterpillars will need another source of food. That’s why it’s wise to plant several plants (Monarch Watch recommends 10) relatively close together (18 to 24 inch spacing).
Plant food for the butterflies, too!
Remember to plant nectar flowering neighbors for your milkweed to help attract butterflies and provide food for them to sip.
Local resources for native milkweed and nectar plants:
Butterfly Farms and the Luca & Micaela Nursery, butterflyfarms.org
California Native Plant Society, canativeseeds.com
Moosa Creek Nursery in Valley Center, moosacreeknursery.com
Native West Nursery, reconnativeplants.com
Learn more:
Xerces Society for Invertebrate Conservation, xerces.org/milkweed
Monarch Joint Venture, monarchjointventure.org
USDA Natural Resources Conservation Service, plant guide on Narrow Leaved Milkweed (Asclepias fascicularis)
US Fish and Wildlife Service, Spreading Milkweed, Not Myths