2019 Urban Tree of the Year - Plant of the Week

American hophornbeam

Ostrya virginiana has common names that include American hophornbeam, Eastern hophornbeam, horn-beam, ironwood, leverwood … a poster child for why common names can be a problem! This is a medium-sized tree in the birch family that has a very large native range east of the Rockies, from Manitoba to Florida.

Ostrya can be found most often as an understory tree and is distinctive for its bark, which looks like thin,

evenly spaced stringy strips lightly exfoliating from the trunk. When we urban foresters bring it out of the

forest and onto the street, it makes a generally oval to rounded tree, about 30 feet (9.1 m) tall at matu-

rity, with somewhat downward drooping branches. The distinctive hop-like flowers that give Ostyra its

common name are most numerous when it has some sunlight, but the tree grows well in light shade, too.

Although it manages dry periods in the shade of the forest, it is not particularly drought-tolerant on the street. However, we at the Urban Horticulture Institute (UHI) have found that it tolerates a wide soil pH range and is pest-free.

Our UHI research on transplantability of Ostrya virgin-iana agrees with others that it is difficult to transplant successfully. In our study, small-caliper (1.5 inch/38

trees showed significant transplant shock in the first year after planting but then recovered in their second year. B&B trees transplanted better in the spring than bare root trees, while B&B and bare root trees transplanted equally well in the fall. Regardless of production method or season, small-caliper trees would be recommended when transplanting.

Nina Bassuk, Director, Cornell Urban

Horticulture Institute

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