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Ostrya knowltonii Cov.

Modern name

Ostrya knowltonii Sarg.

A small deciduous tree 12 to 30 ft high; young shoots downy, greenish brown, becoming grey at two years old; buds cylindrical, very downy. Leaves ovate to oval, toothed, tapered, rounded or slightly heart-shaped at the base, pointed or bluntish at the apex, 1 to 212 in. long, 34 to 114 in. wide, downy on both surfaces; veins in five to eight pairs; stalk 18 to 14 in. long. Male catkins 1 to 114 in. long, with downy stalks and scales. Fruit clusters 1 to 114 in. long, 34 in. wide; the membranous husks or involucres that enclose the nutlets 12 to 34 in. long, oval. Nutlets 14 in. long, hairy towards the apex.

Native of Arizona and Utah; discovered by F. H. Knowlton in 1889 on the southern slope of the Grand Canyon of the Colorado river; introduced to cultivation in N. America in 1914. It differs from the hop hornbeam of the eastern United States (O. virginiana) by its much smaller size, its more abruptly pointed or round-ended leaves with about half as many pairs of veins.



Other species in the genus