Alnus glutinosa
Alnus rubra
black alder, European alder, European black alder
Oregon alder, red alder
dark brown, smooth, becoming darker and breaking into shallow fissures in age;
lenticels pale, horizontal.
gray, smooth, darkening and breaking into shallow rectangular plates in age;
lenticels inconspicuous.
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.
blade ovate to elliptic, 6–16 × 3–11 cm, leathery, base broadly cuneate to rounded, margins strongly revolute, deeply doubly serrate or crenate, with distinctly larger secondary teeth, apex acute to obtuse;
surfaces abaxially glabrous to sparsely pubescent.
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.
formed season before flowering and exposed during winter; staminate catkins in 1 or more clusters of 2–6, 3.5–14 cm; sistillate catkins in 1 or more clusters of 3–8.
ovoid to nearly globose, 1.2–2.5 × 1–1.5 cm;
peduncles 1–10(–20) mm.
ovoid to nearly globose, 1–3.5 × 0.6–1.5 cm;
peduncles 1–10 mm.
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.
buds stipitate, ellipsoid, 6–10 mm, apex rounded, long;
stalks 2–8 mm;
scales 2–3, outer 2 equal and valvate, usually heavily resin-coated.
before new growth in spring.
before new growth in spring.
obovate, wings reduced to narrow, thickened ridges.
ovate or elliptic, wings much narrower than body, irregularly elliptic to obovate, leathery.
= 28.
= 28.
Alnus glutinosa
Alnus rubra
Alnus glutinosa is cultivated as an ornamental tree throughout eastern North America and is available in a variety of cultivars, including cut-leafed and compact-branching forms. This species has also been used extensively to control erosion and improve the soil on recently cleared or unstable substrates, such as sand dunes and mine spoils. It has escaped and become widely naturalized throughout the temperate Northeast, occasionally becoming a weedy pest. In Europe the black alder has served for many centuries as an important source of hardwood for timbers and carved items, including wooden shoes.
Alnus glutinosa has been called A. vulgaris Hill in some older literature; that name was not validly published.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Alnus rubra is the largest alder in North America north of Mexico; it often forms extensive stands along streams and on low-lying flood plains in the Pacific Northwest. The strongly revolute margins of its leaf blades make it easily distinguished from all of the other alders in the flora. It is an important commercial tree; the wood is used to make inexpensive furniture, small wooden items, and paper pulp.
Native Americans used various parts of plants of Alnus rubra medicinally as a purgative, an emetic, for aching bones, headaches, coughs, biliousness, stomach problems, scrofula sores, tuberculosis, asthma, and eczema, and as a general panacea (D. E. Moerman 1986).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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