Asclepias quadrifolia

The common name Whorled Milkweed is derived from the whorls of 4 leaves appearing at the middle of the stem.  Four-leaved milkweed also refers to the same leaves but, in addition, the thick, milky substance or juice that oozes from the stems and leaves when broken.   

An erect, perennial herbs with milky juice and umbrella-like clusters of pink, lavender, or white flowers with pale pink corolla lobes and white hoods.  The 5-parted fruit is dry and inflated, erect, and with many hair-tufted seeds.

Milkweed is perhaps best known as the host plant for the Monarch butterfly.  It is an important food source for the Monarch butterfly caterpillar (Danaus plexippus).  The Monarch begins its northward flight in early spring from its winter nesting sites in Mexico and also southern California.  As they trek north, they will seek out milkweed on which to lay their eggs.  Once the tiny eggs hatch into tiny caterpillars, they will begin to eat the foliage of the plant in order to grow and develop.  Within several days, the once tiny caterpillars will have matured and grown up to 1.5" long and will begin their transformation.  They will seek a protected location, hanging in the form of the letter 'J'.  It is not easily apparent, but while hanging they are forming a web-like structure from which they are hanging.  The caterpillar will then begin to transform into a chrysalis, a clear casing that surrounds the caterpillar.  Metamorphosis takes place, and an adult butterfly will emerge from the chrysalis.  After its wings unfold and dry, the now beautiful Monarch will continue the journey northward until summer's end, at which time the southbound journey will begin.  

Found in: Weedy in disturbed areas, native or naturalized in waste places, roadsides, fields; landscape in flower gardens as herbaceous perennials.

Insects, Diseases, and Other Plant Problems:  Insects, Diseases, and Other Plant Problems: No significant disease problems. Most common milkweed pests (aphids, milkweed beetles, Monarch larvae, and milkweed tussock moth larvae) are not problematic, but both large and small milkweed bugs can be very damaging to seed pods.