Trees , to 30 m; trunks often several, crowns spreading. Bark dark gray, smooth, becoming blackish and breaking into shallow vertical plates in age; lenticels inconspicuous. Winter buds stipitate, ovoid, 4--8 mm, apex rounded; stalks 1.5--4 mm; scales 2, equal, valvate, sometimes incompletely covering underlying leaves, moderately resin-coated. Leaf blade narrowly ovate or lanceolate to narrowly elliptic, 5--9 × 3--6 cm, leathery, base narrowly to broadly cuneate or narrowly rounded, margins flat, sharply and coarsely doubly serrate, rarely evenly and densely short-serrate, major teeth sharp, acuminate, secondary teeth distinctly larger, apex long to short-acuminate, rarely acute; surfaces abaxially glabrous to sparsely pubescent or infrequently villous, moderately resin-coated. Inflorescences formed season before flowering and exposed during winter; staminate catkins in 1 or more clusters of 3--6, 3.5--10 cm; pistillate catkins in 1 or more clusters of 2--7. Flowering before new growth in spring. Infructescences ovoid, ellipsoid, or nearly cylindric, 1--2.5 × 0.8--1.5 cm; peduncles 5--10 mm. Samaras elliptic to obovate, wings narrower than body, irregular in shape, leathery.
Flowering early spring. Sandy or rocky stream banks and moist slopes, often in mountain canyons; 1000--2300 m; Ariz., N.Mex.; Mexico (n Chihuahua and n Sonora).
Alnus oblongifolia is closely related to the Mexican and Central American A . acuminata , with which it has sometimes been confused. It is found only in scattered populations in the temperate deciduous forest vegetation zone of high mountains in the arid Southwest.
Plant: tree to 30 m tall, the trunks often several; bark of older trunks grayish-brown; winter buds rounded apically, the scales 2
Leaves: blades ovate or oblong-ovate to lanceolate, 3-9(-12) cm long, 1.5-6(-7) cm wide, the bases acutish to short-cuneate; margins doubly serrate with major teeth sharp, acuminate, these sometimes scarcely distinguishable among minor teeth
INFLORESCENCE: catkins in clusters of 2-7, with 1 or more clusters on a branchlet; basal fruiting catkins on peduncles (0-)5-10 mm long; individual fruiting catkins spheroid to nearly cylindric, 1-2.5 cm long, 0.7-1.5 cm wide
Flowers: STAMINATE FLOWERS each with (1-)2(-4) stamens; PISTILLATE FLOWERS usually 2 per scale
Fruit: samaras, elliptic to obovate, the wings narrower than the body, irregular in shape
Misc: In mountain canyons along streams and on moist slopes; 650-1950 m (2100-7500 ft); early spring
REFERENCES: Brasher, Jeffrey W. 2001. Betulaceae. J. Ariz. - Nev. Acad. Sci. Volume 33(1)
Common Name: Arizona alder
Duration: Perennial
Nativity: Native
Lifeform: Tree
Wetland Status: FACW
General: Trees, often with several trunks and spreading crowns, reaching 30 m tall, bark dark gray, smooth, breaking into shallow vertical plates in age.
Leaves: Blades narrowly ovate to lanceolate to narrowly elliptic 5-9 cm long by 3-6 cm wide, leathery with a narrowly to broadly cuneate, margins flat, sharply to coarsely doubly serrate, with sharp major teeth and larger secondary teeth, glabrous to sparsely pubescent below.
Flowers: Catkins formed season before flowering and remaining on tree exposed through winter; staminate catkins in 1 or more clusters of 3-6, 3.5-10 cm long; pistillate catkins in 1-or more clusters of 2-7, roughly the same size.
Fruits: Elliptic to ovate samaras with wings narrower than body, irregular in shape and leathery.
Ecology: Found on sandy to rocky stream banks and moist slopes, often in canyons from 5,000-7,500 ft (1524-2286 m); flowers April-June.
Notes: The doubly serrate leaves take you immediately to Betulaceae, while the only other species in our region A. incana ssp. tenuifolia is distinguished by the narrower leaves that are more rounded and lobed at the base, and its being found generally below 7,500 ft (2286 m).
Ethnobotany: Unknown, but other species in the genera have many uses.
Etymology: Alnus is the classical Latin name for the genus, while oblongifolia means oblong leaved.
Synonyms: None
Editor: SBuckley, 2010
