Alders are mostly deciduous shrubs to medium-sized trees of wet areas of the Northern Hemisphere. Most grow quickly and can tolerate poor soils due to their ability to fix nitrogen from the atmosphere. Unfortunately, they generally prefer very wet soils and are poorly suited for most urban landscapes in California. There is one species native to our area, the white alder Alnus rhombifolia. Additionally, Italian alder, Alnus cordata is sometimes used in horticulture. I've never seen an alder locally that impressed me, and reportedly they often suffer from borers in addition to drought stress.