SafePlants

California Milkweed: A Monarch's Lifeline

Milkweeds, particularly those native to California, play a pivotal role in the life cycle of the monarch butterfly. These plants serve as the sole food source for monarch caterpillars, making their conservation essential for the butterfly's survival.

Considerations for Pets

• Milkweed is named for its milky sap, which consists of a latex.

Scientific Name and Common Names

• Scientific Name: Asclepias californica
• Common Names: California Milkweed, Round-hood Milkweed

Taxonomy and Nomenclature

• Family: Asclepiadaceae (Milkweed Family)
• Taxonomic Rank: Subspecies - Asclepias californica Greene subsp. californica

Distribution and Habitat

• Native to California, Nevada, and Oregon.
• Specifically found throughout lower northern, central, and southern California.
• Prefers rockier soil.
• California is a distribution center for six milkweed species used by monarchs.

Ecological Role

• Host plant for monarch butterfly caterpillars.
• The decline of milkweed due to pesticides and development has negatively impacted monarch butterfly populations.
• Planting milkweed, especially California native species, is crucial for supporting monarch populations.

Morphological Characteristics and Growth Habits

• A perennial plant.
• Grows to a height of 1 to 3 feet.
• Produces pale pink flowers.
• Features silvery foliage.

Interactions with Other Organisms

• Monarch butterfly caterpillars exclusively feed on milkweed plants.
• The plant contains cardenolides, which likely serve as a defense mechanism.
• Mentioned in relation to a locust that exudes a poisonous froth, although the exact interaction is not clear.

Further Information

• USDA Natural Resources Conservation Service
• Xerces Society
• University of California Agriculture and Natural Resources
• Weed Science (wsweedscience.org)
• California Invasive Species Council (cal-ipc.org)