white alder
Alnus rhombifolia

Family: Betulaceae.

Type: Deciduous tree.

Branching: Alternate.

Leaves: Margins are wavy, and can be toothed along the waves.

Twig: The twig of the alder is distinct, with long, narrow buds that appear to be on a short stalk. A "moustache" appears to droop over branches at the point where it attaches to the trunk; this can be seen in other species too, but it is particularly distinctive in the alder.

Fruit & Flower: It is monoecious (separate male and female flowers on the same plant). Fruits are small cone-like catkins.

Miscellaneous: In the steeper, faster-flowing riparian areas of Penitencia Creek in Alum Rock Park, a different community composition is observed: sycamore, buckeye, big leaf maple, and coast live oak; less cottonwood, willow, and other species that thrive in high-inundation areas. The species in this area either require highly aerated water, or are more set back from the river. The white alder lives in this habitat. It is associated with nitrogen-fixing bacteria, which is probably part of the reason for its preference for this habitat; those bacteria prefer oxygenated water. Nitrogen is not an issue for the alder, as a consequence, so it drops its leaves green; it doesn't bother to recapture the nitrogen stored in its leaf pigments.