2. Alnus serrulata (Aiton) Willd. (common alder, smooth alder, tag alder)
Pl. 303 e–g; Map
1275
Plants shrubs or
small trees 1.5–3.0(–6.0) m tall, the bark light gray, smooth. Twigs with the
buds 4–5 mm long (excluding the stalk). Petioles 5–18 mm long. Leaf blades
elliptical to rhombic, 5–13 cm long, 3.0–7.5 cm wide, the base rounded to
narrowed, the tip broadly or bluntly pointed to rounded, the margins finely
toothed, not lobed, the teeth 0.2–0.5 mm long, each side of the midrib with 7–11
strong secondary veins. Conelike infructescences 1–2 cm long, the fruits 2.5–4.5
mm long (including the styles), narrowly winged. 2n=28. March–April.
Scattered,
mostly south of the Missouri River (eastern U.S. west to Kansas and Texas;
Canada). Banks of streams, spring branches, and rivers, fens, acid seeps, and
less commonly bottomland forests and margins of lakes and sloughs.
The leaves stay
green later than most of our deciduous species. The underside of the blade
varies from almost glabrous (only scattered hairs on the main veins) to
conspicuously pubescent; the latter form has been called f. noveboracensis
(Britton) Fernald.