Milkweeds are native to all of California, although today they are mostly found in northern California; from the coast into the Sierra, from wetland riparian habitats to pine and mixed conifer forests. They can be found as far east as Texas, and north into the Dakotas and the Great Lakes region, from sea level to 6,000 feet of elevation.
However, the stems and leaves exude milky latex sap when cut (hence their common name), which is mildly toxic. They can cause nausea and vomiting in low doses. Milkweeds plants are toxic to livestock.
If you are lucky enough to see a monarch butterfly, and you follow its fluttery path for a while, you may see it alight on the showy milkweed plant (Asclepias speciosa). You will know this plant by its unmistakably large, showy, thick, greyish, furry leaves, as well as its conspicuous rose-purple flowers which grow in loose clusters at the top of their beefy stems. Milkweeds are the “host plant” of monarch butterflies. That means that the milkweed is the only host for monarch larvae (caterpillars), and an important nectar source for adult monarch butteries.
But milkweed plants are also an important pollinator plant for other butterfly species including checkerspots, painted ladies, swallowtails, viceroy and hairstreaks, as well as European honeybees and native bees, hummingbirds, many species of beetles, and other pollinator insects. Large, dense clumps of milkweed plants will sustain many voracious monarch caterpillars. The monarch butterflies get chemicals from the milkweed plants that make them distasteful to potential predators.
Early Californians used milkweed plants for fiber, food, cordage and even chewing gum. Different parts of the plant were used to heal sores and cuts, and cure warts and ringworms.
Showy milkweeds make great restoration plants because they are perennial, can grow from 2 to 5 feet tall, and have tough extensive root systems with deep tap roots. They are drought tolerant, although they can tolerate moist soils as well. They are a good species for stabilizing and restoring disturbed sites as they have minimal nutrient requirements. They die back to the ground in the winter, and remerge in spring.
Consider planting this important pollinator plant in your garden. It will tolerate many soils types, will grow in full or nearly full sun, will come back year after year. It will add colorful blooms to your landscape from May to September, and the leaves add contrasting color, shape and texture to your existing garden foliage. If you are lucky, or have a dense enough clump of milkweeds, a monarch may come visit your garden.