Alnus glutinosa
Alnus serrulata
black alder, European alder, European black alder
hazel alder, smooth alder
dark brown, smooth, becoming darker and breaking into shallow fissures in age;
lenticels pale, horizontal.
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 broadly elliptic to obovate, 5–14 × 3.5–8 cm, leathery, base broadly to narrowly cuneate, margins flat, serrulate, without noticeably larger secondary teeth, apex obtuse to rounded;
surfaces abaxially glabrous to moderately villous, slightly to moderately resin-coated.
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 2–5, 3–8.5 cm, stamens 4; pistillate catkins in 1 or more clusters of 3–5.
ovoid to nearly globose, 1.2–2.5 × 1–1.5 cm;
peduncles 1–10(–20) mm.
ovoid-ellipsoid, 1–2.2 × 0.6–1.2 cm;
peduncles 1–3(–5) 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 to obovoid, 3–6 mm, apex mostly rounded;
stalks 2–4 mm;
scales 2, equal, valvate, moderately to heavily resin-coated.
before new growth in spring.
before new growth in spring.
obovate, wings reduced to narrow, thickened ridges.
obovate, wings narrower than body, irregularly elliptic or obovate, leathery.
= 28.
= 28.
Alnus glutinosa
Alnus serrulata
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.)
Primarily an Atlantic coastal species, Alnus serrulata also grows along the St. Lawrence river system and the lower Great Lakes westward to the dunes of southern Lake Michigan, and across the southern states to the Gulf Coast and east Texas. Alnus serrulata was erroneously called A. rugosa in a number of earlier floristic works (J. K. Small 1903, 1933; N. L. Britton and A. Brown 1896, 1913; and B. L. Robinson and M. L. Fernald 1908), and the mistake was perpetuated in both editions of Flora Europaea (T. G. Tutin et al. 1964–1980, vol. 1; 1993+, vol. 1).
Alnus incana subsp. rugosa hybridizes with A. serrulata (= Alnus serrulata var. subelliptica Fernald). Extensive hybrid swarms occur where the ranges of these species overlap, including the area along the St. Lawrence River and the southern edge of the Great Lakes (F. L. Steele 1961). R. H. Woodworth's conclusion (1929, 1930) that apomixis occurs in A. serrulata resulted from his use of material selected from a hybrid swarm. The remainder of the species appears to reproduce normally. The two species and their hybrids are usually easily distinguished by leaf shape and margin characters.
Various preparations of Alnus serrulata were used medicinally by Native Americans to alleviate pain of childbirth, as a blood tonic, an emetic and purgative, for coughs and fevers, to stimulate kidneys, to bathe hives or piles, for eye troubles, indigestion, biliousness, jaundice, heart trouble, mouth soreness in babies, and toothaches, to lower blood pressure, and to clear milky urine (D. E. Moerman 1986).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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