In a season when California's native maples, cottonwoods, oaks, dogwoods, and aspens are staging a spectacular color show, leaves on alder trees remain green, even when they fall. Before falling, the leaves of most deciduous trees shunt hard-won nutrients back into branches and roots for winter storage. But with nitrogen to spare, alders are not so stingy, shedding leaves still laden with the nutrient.
Traditional farmers value the tree.
In the highlands of Guatemala, farmers mulch vegetables with alder leaves and spare the trees when clearing fields for crops. A study in Sikkim in the Himalayas found that cardamom bushes growing under alders produced over twice the yield of bushes grown beneath other trees. Most aquatic insects that live as larvae in California's rivers emerge as winged adults in spring through late summer. But the October caddisfly is an exception. On fall evenings in north state rivers such as the Pit and lower Sacramento, these inch-long insects with fuzzy wings and orange bodies pull themselves out of their pupal cases and fly into the air.