Narrow-leaf milkweed (Asclepias fascicularis)

Narrowleaf Milkweed (Asclepias fascicularis) is a flowering perennial best known for the Monarch butterflies it will attract into the garden. Its long, thin pointed leaves give the plant a soft, wispy look. It blooms in summer to fall, with clusters of lavender or pinkish white flowers, each one an interesting button shape. The fruits are smooth pods, which split open to spill seeds along with plentiful silky hairs that may carry the seeds through the air.

This plant grows fast to 3 feet tall and is dormant in winter, often dying back to the ground. It will take full sun but is adaptable to most conditions, being easy to grow in soils with good drainage, even with no summer water. It can self-seed if the seed pods are not removed

This species is probably the single most important host plant for Monarch Butterflies in California, attracting them and hosting their caterpillars. It is crucial to not use any pesticide on or around the plant, because doing so will be fatal to the caterpillars. The plant also provides resources for many beneficial creatures, including native bees. Don't cut the dry stems down too soon as Orioles may use them for nesting.

Description from Calscape