White alder

[ Alnus rhombifolia ]

Out in the bare-limbed forests, only the alders look alive. Bedecked with 7-inch-long greenish catkins that droop elegantly from every branch tip, alders take on an oddly festive appearance in a dreary season. Properly speaking, these catkins are male flowers that will soon open to release pollen onto the smaller, conelike female catkins. By appearing in midwinter, long before leaves emerge, alders ensure that wind blowing through open branches will maximize dispersal of their microscopic pollen grains. Found along streams throughout California, white alders quickly invade sites cleared by floods or other disturbances.

Natural History

Alder roots form a special association with an actinomycete fungus that transforms atmospheric nitrogen into a nutrient that plants and animals can use. Alders and their fungi play a key role in creating healthy ecosystems.

Key Characteristics

The smooth, pale-gray bark of alders is well marked with upside-down Vs above each branch, giving their trunks the appearance of having many moustaches. Leaves are elmlike and oval, with serrated edges.