Asclepias fascicularis is a species of milkweed known by the common names narrowleaf milkweed and Mexican whorled milkweed. It is a flowering perennial sending up many thin, erect stems and bearing distinctive long pointed leaves which are very narrow and often whorled about the stem, giving the plant its common names. It blooms in clusters of lavender or lavender-tinted white flowers which have five reflexed lobes that extend down away from the blossom. The fruits are smooth milkweed pods which split open to spill seeds along with plentiful silky hairs.

Asclepias fascicularis is a specific food and habitat plant of the monarch butterfly. It is cultivated by specialty nurseries as an ornamental plant and used in butterfly and wildlife gardens, and in native and water conservation gardens, and natural landscape projects. 

Source: Wikipedia

CAUTION: Milkweed may be toxic humans and animals if ingested and the sap can be a skin irritant. 

Source: UCANR