Corylus americana
Corylus
American hazel or hazelnut, American hazelnut, noisetier d'amérique
filbert, hazel, hazelnut
grayish brown, thin, smooth, close, breaking into vertical strips and scales in age;
prominent lenticels absent.
ascending;
twigs pubescent, covered with bristly glandular hairs.
, branchlets, and twigs nearly 2-ranked to diffuse;
young twigs differentiated into long and short shoots.
blade broadly ovate, often with straight sides and slight lobes near apex, giving them squarish appearance, 5–16 × 4–12 cm, moderately thin, base narrowly cordate to narrowly rounded, margins sharply serrate or obscurely doubly serrate, apex abruptly to long-acuminate;
surfaces abaxially sparsely to moderately pubescent, velutinous to tomentose along major veins and in vein axils.
blade broadly ovate with 8 or fewer pairs of lateral veins, 4–12 × 3.5–12 cm, thin, bases often cordate, margins doubly serrate, apex occasionally nearly lobed;
surfaces abaxially usually pubescent, sometimes glandular.
staminate catkins lateral along branchlets on very short shoots, usually in clusters of 1–2, 4–8 × 0.5–0.8 cm;
peduncles mostly 1–5 mm.
staminate catkins on short shoots lateral on branchlets, in numerous racemose clusters, formed previous growing season and exposed during winter, expanding well before leaves; pistillate catkins distal to staminate catkins, in small clusters of flowers and bracts, reduced, only styles protruding from buds containing them at anthesis, expanding at same time as staminate.
in catkins 3 per scale, congested;
stamens 4, divided nearly to base to form 8 half-stamens;
filaments very short, adnate with 2 bractlets to bract.
2 per bract.
compact clusters of several fruits, each subtended and surrounded by involucre of bracts, bracts 2, hairy [spiny], expanded, foliaceous, sometimes connate into short to elongate tube.
relatively thin-walled nuts, nearly globose to ovoid, somewhat laterally compressed, longitudinally ribbed.
buds containing inflorescences broadly ovoid, 3–4 × 3–4 mm, apex obtuse to rounded.
buds sessile, broadly ovoid, apex acute;
scales several, imbricate, smooth.
in clusters of 2–5, sometimes partially visible;
bracts much enlarged, leaflike, distinct nearly to base, slightly longer than to 2 times length of nuts, apex deeply and irregularly laciniate;
bract surfaces downy-pubescent, abaxially stipitate-glandular.
nearly white to light brown, moderately hard, heavy, texture fine.
= 11.
= 22, 28.
Corylus americana
Corylus
Corylus americana is a weedy species, sometimes considered a pest in carefully managed forests. The nuts are smaller but of the same general quality and flavor as commercial filberts (Corylus maxima Miller and C. colurna Linnaeus).
Native Americans used Corylus americana medicinally for hives, biliousness, diarrhea, cramps, hay fever, childbirth, hemorrhages, prenatal strength, and teething, to induce vomiting, and to heal cuts (D. E. Moerman 1986).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Species ca. 15 (3 in the flora).
Corylus differs from other Betulaceae in various features, most notably in the infructescences, which consist of small clusters of well-developed nuts, each enclosed by a loose involucre of leaflike bracts. As in Ostrya, the staminate catkins are formed during the summer and are exposed through the winter prior to anthesis. In Corylus, however, pistillate catkins develop at the same time as the staminate, and they consist of only a few flowers, protected by the scales of special buds rather than being arranged in elongate pistillate catkins. The staminate flowers are unique in the family in that well-developed sepals are occasionally present, clearly defining the three individual flowers that make up each cymule.
A longstanding disparity occurs in the literature regarding the diploid chromosome number found in Corylus species, with both 2n = 22 and 2n = 28 being cited. J. G. Packer (pers. comm.) believes that the 2n = 28 for several species (R. H. Woodworth 1929c) was in error because of a misinterpretation of Woodworth's meiotic preparations, a number of which actually indicate eleven haploid chromosomes. Woodworth's count may be largely, if not entirely responsible for the persistence of this number in the literature.
The genus consists of three major subgroups, the first composed of shrubby plants having a short, open involucre of two bracts surrounding the fruits (Corylus sect. Corylus). Members of Corylus sect. Tuboavellana Spach are of similar habit but have the involucre modified into a tubular beak, and Corylus sect. Acanthochlamnys Spach is characterized by densely spiny bracts. Recent treatments have avoided applying sectional names. The genus as a whole should be considered for taxonomic revision.
Corylus is the source of hazelnuts and filberts. Commercial filberts (C. colurna Linnaeus and C. maxima Miller) are cultivated in various parts of the world, particularly Turkey, Italy, Spain, China, and the United States. Wild hazelnuts (C. americana and C. cornuta) are smaller but similar in flavor to those of the cultivated species.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Fruit surrounded by soft bristly involucre connate to summit into narrow tube 2–5 times length of fruit; branchlets and petioles glabrous to pubescent, with or without glandular hairs. | C. cornuta |
1. Fruit surrounded by involucre of 2 downy, expanded, foliaceous bracts, distinct nearly to base; branchlets and petioles covered with bristly glandular hairs. | → 2 |
2. Involucre slightly longer than to 2 times length of fruit; staminate catkins mostly in groups of 1–2, peduncles 5 mm or shorter; slender native shrubs to ca. 3 m. | C. americana |
2. Involucre shorter than to only slightly longer than fruit; staminate catkins mostly in groups of 2–4, peduncles more than 5 mm; broad, spreading, introduced shrubs to ca. 5 m. | C. avellana |
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