Asclepias californica aka California Milkweed

Asclepias californica belongs to the dogbane family, Apocynaceae. It is a perennial, so it lives for more than two years. People call it California milkweed or Greene’s milkweed. Kew lists California as its native range. Plants For A Future adds northern Baja California, Mexico. It grows on dry slopes below about 7,220 feet [2,200 metres]. Kew puts it in a subtropical climate. It is not native to Britain or Ireland.

The plant grows about 1.6 feet [0.5 metres] tall. The sources give no width or growth rate for this species. Its stems and leaves hold latex, a milky sap. This sap has uses beyond the garden. The sources say little about this species’ leaf shape or stems. They give no account of its flowers or fruit as a whole. Each flower has both male and female organs. Bees and other insects help pollinate the flowers. These include moths and butterflies. The sources give no months for bloom.

Plants For A Future says sandy soil suits this plant. The soil must drain well, but it can be poor. The stated pH range goes from mildly acid to mildly alkaline. The plant can grow in full sun or light shade. The same source says both dry and moist soil suit it. The sources give no firm British hardiness rating. Plants For A Future says its hardiness in Britain is still unclear. Much of its other growing advice is for the genus. Those notes do not show how much frost this species can bear. Nor do they show which pests affect it.

Plants For A Future lists garden beds as a place to grow it. Its flowers draw insects that pollinate them, giving it a role there. The source tells how to grow it from seed under glass. Stored seed may need two to three weeks of cold treatment. Seeds take one to three months to sprout at 18°C. It also describes splitting plants in spring. Yet it warns against disturbing the roots. The sources name no pest or disease for this species.

Plants For A Future records a use for roasted leaves: chewing. It also reports that people boil the sap into gum. These uses do not prove that raw plant matter is safe. Its warning of harm applies to the genus. It does not confirm that this species is toxic. One record describes a past use of dried plant powder on spider bites. This does not show that it helps treat them. Latex from the stems and leaves has also supplied rubber.