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Trees of Yosemite (1932, 1948) by Mary Curry Tresidder

[Birch Family]

White Alder

Alnus rhombifolia Nutt.

White Alder Branch About 1/2 Natural Size

The alder belongs to the birch family. The field name of “White Alder” was suggested by Sudworth in the absence of any other, on account of the pale, rather whitish-green foliage. The species name rhombifolia refers to the shape of the leaf.

The tree has a rather straight, gray trunk one to three feet in diameter, and may range from thirty to seventy feet in height, with a decidedly rounded crown of rustling, leafy branches.

The leaves are oblong-ovate and are minutely hairy. The veins run straight from the central vein of the leaf to the margin, which is toothed correspondingly. The leaves are shed in autumn, but they do not change color particularly before they fall.

Staminate and pistillate flower-clusters are borne on different parts of the same branch; the former, opening in midwinter, are pendent, terminating a branchlet; the latter are lower down on the twig, and develop into small, erect cones, half an inch to an inch in length, whose scales open in late autumn or early spring. These tiny cones fall entire.

White Alder occurs along streams in the canyons of the Sierra Nevada in the Transition Zone, as in the lower part of Illilouette Canyon and along the Merced River near Happy Isles, where its drooping lower branches cast a dappled shade upon the waters.

In the winter months the pine siskins find the White Alder one of their main sources of food supply. A Rock of them will perch in the branches of a single tree and shake the cones until the seeds fall. In spring the drooping clusters of catkins are besieged by black-headed and evening grosbeaks, and by little groups of purple finches.

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