Trees , to 20 m; trunks often several, crowns narrow. Bark dark brown, smooth, becoming darker and breaking into shallow fissures in age; lenticels pale, horizontal. Winter buds stipitate, ellipsoid to obovoid, 6--10 mm, apex obtuse; stalks 2--5 mm; scales 2--3, outer 2 equal, valvate, usually heavily resin-coated. Leaf blade obovate to nearly orbiculate, 3--9 × 3--8 cm, leathery, base obtuse to broadly cuneate, margins flat, coarsely and often irregularly doubly serrate to nearly dentate, major teeth acute to obtuse or rounded, apex often retuse or obcordate, or occasionally rounded; surfaces abaxially glabrous to sparsely pubescent, often more heavily on veins, both surfaces heavily resin-coated. Inflorescences formed season before flowering and exposed during winter; staminate catkins in 1 or more clusters of 2--5, 4--13 cm; pistillate catkins in 1 or more clusters of 2--5. Flowering before new growth in spring. Infructescences ovoid to nearly globose, 1.2--2.5 × 1--1.5 cm; peduncles 1--10(--20) mm. Samaras obovate, wings reduced to narrow, thickened ridges. 2 n = 28.
"Tree, with young parts very glutinous; lvs broadly oval to obovate or subrotund, broadly rounded above or retuse, broadly cuneate to rounded at base, finely serrate, with 5–8 principal veins on a side; fruiting catkins very glutinous, evidently pedunculate in axillary infls, 1.5–2.5 cm, 10–13 mm thick; frs elliptic or suborbicular, 2.5–3.5 mm, narrowly bordered; 2n=28. Native of Eurasia and n. Afr., planted especially along roadsides and occasionally escaped in our range. (A. alnus; A. vulgaris)"
Tree, 20-30 m high; young growth glutinous; monoecious. Leaves petiolate; blade elliptic to broadly ovate, 60-120 mm long, apex truncate, base cuneate, margins shallowly toothed, sticky when young, later glossy green; petiole up to 50 mm long. Flowers: male catkins 50-100 mm long, pendulous, reddish; female catkins 200 mm long, dark brown to black; Nov.-May. Fruit cone-like with 5-lobed scales, persistent; nutlets winged.
|Black alder, European alder|