- Author: Linda Lewis Griffith
- Editor: Noni Todd
by Linda Lewis Griffith UCCE Master Gardener
Common Name: California Narrowleaf Milkweed and Mexican Whorled Milkweed
Planting Zone: USDA 7-10
Size: 3-5 feet tall, with narrow 5-inch long leaves and 5-inch white or lavender flower clusters
Bloom Season: Summer
Exposure: Full sun. Produces fewer flowers if planted in the shade.
Pruning Needs: None
Water Needs: Drought tolerant once established. Able to survive in clay soils and seasonal floodplains.
Narrative: Milkweed is a native perennial that ranges from Southeast Washington and Idaho, through California, Oregon, Nevada and into Baja California. It is found on dry ground and sunny areas in valleys and foothills. Milkweed is deciduous and will die back in the winter. It is deer resistant and an excellent choice in bird and butterfly gardens, as well as native plant and drought tolerant gardens. It is crucial not to use any pesticide on or nearby this plant as doing so will be fatal to the insects it attracts.
Milkweed plays a crucial role in the life cycle of Monarch butterflies. Females lay their eggs on the underside of young healthy leaves. When the eggs hatch, larvae feed on the plants, generally eating them to the ground. It's advised to plants milkweed in clumps because, when caterpillars feel threatened, they “play possum” and drop to the ground. They may not be able to find their way back up the milkweed stems unless plants are densely packed.
Milkweed contains a white, gummy sap that is poisonous to livestock. The toxin, cardenolide, induces vomiting in low doses and death in larger amounts. As a result, milkweed was once classified as a noxious weed and efforts were taken to eradicate it. Cardenolide is the same chemical that makes the caterpillar's flesh distasteful to most animals. Monarch, Queen and Viceroy butterflies are all poisonous and have developed similar wing patterns that warn predators of their poisonous properties, hence protecting them from predation.
Milkweed is easily propagated by collecting seeds after the pods have ripened and sewing them directly into the ground in the fall./h1>/span>