Flora of North America species comparison

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Alnus rhombifolia

California alder, white alder
Habit Trees, to 35 m; trunks often several, crowns spreading, open.
Bark

light gray, smooth, becoming darker and breaking into scales in age;

lenticels inconspicuous.
Leaf

blade narrowly elliptic to rhombic, rarely ovate, 4–9 × 2–5 cm, base cuneate to rounded, margins flat, finely serrate or serrulate, sometimes slightly lobed, without noticeably larger secondary teeth, apex acute or obtuse to rounded;

surfaces abaxially sparsely pubescent to villous.
Inflorescences

formed season before flowering and exposed during winter; staminate catkins in 1 or more clusters of 3–7, 3–10 cm, stamens 2, or 4 with 2 reduced in size; pistillate catkins in 1 or more clusters of 2–6.
Infructescences

ovoid to nearly cylindric, 1–2.2 × 0.7–1 cm;

peduncles 1–10 mm.
Winter

buds stipitate, ellipsoid to obovoid, 3–9 mm, apex rounded;

stalks 3–5 mm;

scales 2, equal, valvate, sometimes incompletely covering underlying leaves, moderately to heavily resin-coated.
Flowering

before new growth in spring.
Samaras

broadly elliptic, wings narrower than body, irregular in shape, leathery.

Alnus rhombifolia
Phenology Flowering early spring.
Habitat Open, rocky stream banks and adjacent (often rather dry) slopes
Elevation 100–2400 m (300–7900 ft)
Distribution
from FNA
CA; ID; MT; OR; WA
[WildflowerSearch map]
[BONAP county map]
Discussion

Alnus rhombifolia is the common alder throughout the dry Mediterranean climatic zone of coastal western United States. Mexican populations are not known, but because A. rhombifolia has been collected as far south as San Diego, California, it should be expected in adjacent Baja California.

Native Americans used various parts of Alnus rhombifolia medicinally for diarrhea, consumption, and burns, as a blood purifier, an emetic, and a wash for babies with skin diseases, and to facilitate childbirth (D. E. Moerman 1986).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 3.
Parent taxa Betulaceae > subfam. Betuloideae > Alnus
Sibling taxa
A. glutinosa, A. incana, A. maritima, A. oblongifolia, A. rubra, A. serrulata, A. viridis
Synonyms A. rhombifolia var. bernardina
Name authority Nuttall: N. Amer. Sylv. 1: 49. (1842)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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