Tree of Merit: Hophornbeam (Ostrya virginiana)
Story and photos by Cene Ketcham, Extension Arborist, Casey Trees
Hophornbeam (Ostrya virginiana) is an attractive small to medium tree with big urban credentials. However, compared to other urban-tough trees like red maple, ginkgo, and honeylocust, hophornbeam has been regrettably underutilized.
Sometimes called “ironwood” like its bottomland cousin, Carpinus caroliniana, hophornbeam’s hard, dense wood makes it highly resistant to damage from wind, snow, and ice. Largely insensitive to site conditions, it takes indignities like air pollution, compacted soils, and droughty conditions in stride. Hophornbeam grows well in full sun to part shade, needs little pruning, and is generally free of insect pests and diseases. An excellent street tree in warmer climates, hophornbeam is intolerant of salt so should be avoided where road salting is common.
Though transplanting can be tricky—hophornbeam often appears on “fall hazard” lists—once established, it requires very little care. Transplant difficulties may be mitigated by root pruning in spring and by digging later in the fall season after the tree is fully dormant. A Cornell University study published by Bassuk and Buckstrup in 2000 showed that in Ithaca, New York, fall-planted hophornbeam B&B and bare root trees were equally successful, while spring-planted hophornbeam trees were more successful when planted B&B.
In the woods, hophornbeam is an understory tree that grows on upland slopes. It is capable of reaching 60 ft (18.3 m), but typical heights in cultivation are 25–40 ft (7.6–12.2 m). The tree is pyramidal to rounded in profile, achieving a width generally 2/3 of height. It has an extremely large natural range, extending north to south from southern Manitoba to the Gulf Coast and stretching east as far as Canada’s Maritime Provinces and the Atlantic Coast of the United States. It is hardy for Zones 3–9, which encompasses most of the U.S. and southern Canada, making it quite geographically versatile as well.
Hophornbeam is not tremendously showy except in its yellow fall foliage, but it does have subtle beauty. Its bark is a defining feature—dark brown and shreddy, its strips peel up at the ends and swirl around the trunk. Neither its male nor female flowers are remarkable, though its catkins are a good winter ID characteristic—small and grouped in threes, they look like bird feet. The fruit is contained in a chain of inflated, papery sacs resembling hops and giving the tree its common name. These interesting fruits are present through winter and invite close inspection. However, they have hairs that can be a mild skin irritant when newly formed in fall, so handle with care. The small, pointed buds have tiny lengthwise striations, which are quite distinctive and attractive when viewed through a hand lens.
Long neglected because of its reputed difficulty in transplanting and its slow growth, hophornbeam rewards those who make the effort by providing years of trouble-free service. Equally appropriate and attractive in natural areas, landscape settings, and on the streetside, its versatility and toughness make it an excellent addition to any plant palette.