Asclepias fascicularis

Asclepias fascicularis (also known as the narrow-leaf milkweed or Mexican whorled milkweed) is a species of milkweed plant. It belongs in the subfamily Asclepiadoideae.  It is native to the western United States.  It blooms from June to September.  This species is found in dry areas and valleys.

Other websites

Asclepias fascicularis at USDA PLANTS Database
Asclepias fascicularis at Treatment from the Jepson Manual

f