Before Americans of European descent began actively farming and developing the beautiful, temperate California coast, vast stretches from San Francisco to the Mexican border were covered with a low-growing, aromatic plant community called coastal sage scrub. The ecosystem supported an array of seasonal wildflowers, such as California poppy, lupins, wild onions and sego lilies.

Because of its gentle topography and proximity to coastal cities, however, two-thirds of the coastal sage scrubland has already been converted to housing or farming, said Edith Allen, UC Cooperative Extension specialist in the Department of Botany and Plant Sciences at UC Riverside. The remaining coastal sage...