Table of Contents for California Milkweed (Asclepias californica)
California Milkweed (Asclepias californica) is a herbaceous perennial that is found in California and adjacent parts of Mexico. This plant is a host to the Monarch butterfly (Danaus plexippus) and Queen butterfly (Danaus gilippus). It can grow from 3 to 4 feet tall. The flowers have been described as lavender, pink, white, green, maroon, red, purple and violet and bloom from April to July. It is hardy in zones 7-10.
Taxonomy and Naming of California Milkweed (Asclepias californica)
Taxonomy
California milkweed (Asclepias californica) was named and described by Edward Lee Green, an American botanist, in 1893. The original specimen was collected in the “mountains east of San Diego, California” (Heller and Beveridge 1917). The species has kept this name since. This plant is a member of the Dogbane Family (Apocynaceae).
Subspecies (Woodson 1954)
- Asclepias californica ssp. californica: This subspecies occurs in southern California and has a subsessile flower.
- Asclepias californica ssp. greenei: This subspecies occurs in northern California and has a stipitate flower.
Meaning of the Scientific Names and Common Names
Scientific Name
The genus name, Asclepias, is named for the Greek god of healing, Asklepios (Flora of Wisconsin). The species name, californica, is Latin for the native range of the species.
Common Name and Alternative Names
The common name describes the native location of the plant. Round hood milkweed, another common name, describes the flower of the plant. Edward Greene in his description of the species called this species California silkweed, presumably referring to the silky seeds. Another name is Woolly Milkweed (Higgins 1949), which describes the grayish pubescence of the stem and leaves.
Physical Description
Description
- Plant Type: This plant is a herbaceous perennial.
- Height: 2 to 4 feet
- Stem: covered in dense gray pubescence
- Leaves: The leaves are opposite, simple, subsessile, entire, and ovate, oval to elliptic-lanceolate. They range in size from 1.5 to 7 inches in length and 1 to 3 inches in width. The leaves are pubescent when young but become hairless with age (Woodson 1954).
- Flower color: The flowers are highly variable in color and range from white, pink, lavender, green (Hall 1921), purple (Jepson eFlora), red (wildflower.org), maroon (California Native Plant Society 2006), and violet (Las Pilitas Nursery).
- Blooming period: This plant blooms from March to July.
- Fruiting type and period: This plant has follicles that mature in the late summer and fall.
Range of California Milkweed (Asclepias californica) in the United States and Canada
This milkweed species grows in the state of California and the adjacent areas of Mexico.
Habitat
This species grows in open areas such as grassy slopes, roadsides, pastures, woodlands, and disturbed places.
Hosted Insects
This species is a host for the Monarch Butterfly (Danaus plexippus) and the Queen Butterfly (Danaus gilippus).
Other Supported Wildlife
This species is a nectar source to bees in the summer and fall.
Frequently Asked Questions
Is this plant poisonous?
Like other milkweeds, it has cardiac glycosides (cardenolides) and is considered to be poisonous with ingestion. This plant has been documented as being poisonous to cattle (Schneider 1912) and is likely detrimental to pets as well.
Does this plant have any ethnobotanical uses?
The Native American Ethobotanical Database notes that this species has been used as a candy and for skin diseases.
How is this plant distinguished from other milkweeds?
California milkweed has a fairly restricted range. The plants are densely tomentose and have large flowers. This species also lacks the “horn” on the flower hood that is common to other milkweeds (Jepson 1893).
Is this plant invasive?
This species has a restricted range and there is nothing in the literature indicating that it may be invasive.
Gardening with California Milkweed (Asclepias californica)
Hardiness
This species is hardy in zones 7-10. If your garden is within these zones and you have the right growing conditions (soil, moisture and exposure), you may well be able to grow this plant. However, if planted outside of its range, the hosted species may not recognize the plant or be harmed by ingesting a different species with an unfamiliar chemical composition.
Optimal Conditions
This species grows best in places it can receive full sun. It generally needs dry sandy soil, but can also handle clay.
References
- California Native Plant Society. 2006. In the field section. Mimulus Memo Fall 2006.
- Hall, Harvey Monroe. 1921. Rubber Content of North American Plants. Carnegie Institution of Washington publication 313.
- Greene, Edward Lee. 1893. The Vegetation of the Summit of Mount Hamilton. Erythea 1: 77-97.
- Heller, Amos Arthur and Kennedy P. Beveridge. 1907. Botanical Exploration in California Season of 1907. Muhlenbergia 2: 307.
- Higgins, Ethel Bailey. 1949. Annotated Distributional list of the Ferns and Flowering Plants of San Diego County, California. Occasional Papers of San Diego Society of Natural History.
- Schneider, Albert. 1912. Pharmacal Plants and their Culture. California State Board of Forestry.
- Woodson, Robert E. 1954. The North American Species of Asclepias L. Annals of the Missouri Botanical Garden 41: 1-211.
