Characteristics of White Alder Tree (Alnus rhombifolia) in the Wild

Alnus rhombifolia
White alder (Alnus rhombifolia) is an alder tree native to western North America, from British Columbia and eastern Washington to western Montana, southeast to the Sierra Nevada, and south through the Peninsular Ranges and oases of the Colorado Desert in Southern California. It grows in riparian habitat zones at altitudes ranging from 100-2,400 m above sea level.

White alder is a medium-sized deciduous tree that is believed by the Plateau Indians as one of the ingredients for the treatment of women’s health.

White alder is closely related to Red Alder, the difference is the leaf margins. Alder trees can fix nitrogen from the air and thrive in infertile soils.

 

Characteristics of White Alder Leaf

Alnus rhombifolia Leaf
Source: inaturalist.org/rangerjoey

The leaves are alternate, rhombic, elliptical, 4-10 cm long, and 2-5 cm wide, with finely serrated margins and rounded to a sharp apex. The leaves are green and not very hairy.

 

Characteristics of White Alder Flower

Alnus rhombifolia Flower
Source: inaturalist.org/tarantulalover

The flowers are clustered. The flowers are male, pendulous, 3-10 cm long, yellowish, and produced in clusters of two to seven, pollinating in early spring, before the leaves appear. The female flowers are ovate, ripen in autumn, and are 7-10 mm long and wide, resembling small coniferous cones.

 

Characteristics of White Alder Fruit

Alnus rhombifolia Fruit
Source: inaturalist.org/tarantulalover

The tiny winged seeds spread in winter, leaving an ancient, blackish “cone” of wood on the tree for up to a year.

 

Characteristics of White Alder Tree

Alnus rhombifolia Tree
Source: inaturalist.org/gx_kai

The white alder tree can grow into a medium-sized tree with a height of 15-25 meters, with pale gray bark, smooth on young trees, and rough on older trees.

 

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