Showy milkweed
Asclepias speciosa
Care
full sun
very low
Fast, Medium; Tolerates clay soil but performs best with good drainage.
4–6ft tall , 4–4ft wide
Jun-Aug
Deciduous
Resistant
Prized
Riparian areas and grasslands throughout northern and central California below 6000 ft elevation, extending to British Columbia and east to the Midwest.
Care Guide
Planting
Plant your showy milkweed in full sun in a location with fast or medium drainage - it tolerates clay soil but performs best when well-drained. Space plants to accommodate their mature size of 4–6 feet tall and their spreading habit via underground rhizomes. The Bay Area's mild winters mean you can plant in fall or early spring; avoid planting during summer heat stress.
After Planting
Water weekly during your first summer to establish the plant, then cut back to no more than twice monthly once established - this is a very low water plant that thrives on neglect. In winter, when the plant goes dormant and dies back, you can prune large clumps during this dormancy season. The #1 mistake is overwatering: showy milkweed wants dry conditions, so let the soil dry out between waterings. If seed pods appear and you want to prevent self-sowing, remove them; otherwise, let them stay for the wildlife value.
Endangered & Threatened Species Supported
California Species of Special Concern; monarch populations declining
Wildlife Supported
Insects
Essential larval food plant for multiple generations; critical during spring northward migration (Feb-Apr) and fall southward migration (Aug-Oct)
Visits flowers for nectar during adult foraging; multiple generations utilize milkweed as fuel source
Adult nectar source supporting multiple broods; important for maintaining populations in California habitats
Nymphs and adults extract seeds and developing pods; population density increases through fall
Birds
Year-round nectar source; especially important during winter months when few other plants bloom in California
Spring/early summer migration staging and breeding season nectar source in foothill habitats
Vagrant eastern species; occasional migrant utilizing milkweed nectar during spring and fall passage