Alnus rhombifolia Nutt.

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Tim Baxter & Hugh A. McAllister (2021)

Recommended citation
Baxter, T. & McAllister, H.A. (2021), 'Alnus rhombifolia' from the website Trees and Shrubs Online ( Accessed 2023-12-10.

A tree 30 to 100 ft high, forming a thin, spreading, round-topped head of branches, pendulous at the ends; young branches at first covered with pale hairs which soon fall away. Leaves ovate, oval, or rounded, ordinarily 2 to 4 in. long, about two-thirds as wide; usually pointed (sometimes rounded) at the apex, tapered at the base, unevenly or doubly toothed; dark shining green (but at first very hairy) above; paler, yellowish, and permanently downy beneath. Male catkins two to seven in a cluster, opening on the naked shoots early in spring, each catkin 3 to 5 in. long; stamens two, rarely three. Fruits 13 to 34 in. long, three to seven together.

Native of western N. America. The leaves occasionally approach the diamond shape indicated by the name, and on vigorous shoots are up to 5 in. long. According to Jepson, this alder keeps to streams which do not run dry, forming files of trees in mountain gorges which are ‘to the traveller a reliable sign of water’. It is very rare in cultivation, the plant supplied for it in this country and on the continent being, as a rule, A. rubra.