Ironwood, hop-hornbeam

Ostryer de Virginie

Ostrya virginiana (Mill.) K. KochBetulaceae (birch family)

Origin: Eastern North America (native in Ontario)


Hop-hornbeam is a small tree with a wide spreading conical crown.

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Leaves are oval, with pointed tips, saw-toothed edges and short leaf stalks.

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Male flowers are borne in catkins that hang in groups of 1 to 3. Female flowers are inconspicuous.

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Fruits are inflated paper-like sacs, borne in hanging clusters.

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Hop-hornbeam is a small tree, up to 12 m (39') high and about 13 - 25 cm (5" - 10") in diameter.

The crown is conical and wide-spreading

The bark is grey-brown and shaggy, with thin vertical peeling strips.

Twigs are reddish-brown, with buds angled outwards. Buds are pointed, 3 - 4 mm (just over 1/10") long.

Like beech and oak, hop hornbeam leaves sometimes persist on the tree in winter.

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Leaves are oval, 7 - 12 cm (2 3/4" - 4 3/4") long, tapering to a pointed tip, with hairy undersides.

Leaves have short stalks and saw-toothed edges.

Leaves are arranged alternately on the branch.

In fall, the leaves turn yellow.

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Male flowers are borne in catkins that hang in groups of 1 to 3, elongating to 5 cm (2") in Spring when mature.

Female flowers are borne in separate inconspicuous clusters on the same branch as male catkins.

Catkins release pollen in early spring as the leaves unfurl.

Short compact catkins bearing next year's male flowers develop late in the season and are conspicuous all winter.

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Fruits are inflated green or brown paper-like sacs, 1 - 2 cm (about 1/2") long, borne in dangling clusters.

Each cluster is 3 - 5 cm (1 1/4" - 2") long, and bears 4 to 20 sacs, each with a nutlet inside.

Nutlets are 5 - 8 mm (about 1/4") long.

Fruits mature in September. The sacs fall in winter, but some may remain on the tree.

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Hop-hornbeam is the only species of the genus Ostrya that is native to Canada. It is slow-growing and fairly long-lived, reaching 150 years.

Derivation of names

This species serves as an example of the confusion that can be caused by using common names. Ostrya virginiana is often called ironwood, a name that has been applied to dozens of tree species worldwide and several in North America, including the native Carpinus caroliniana (which is also called blue-beech, although it is not a beech). Carpinus caroliniana has also been referred to as American hornbeam, which is similar to other common names for Ostrya virginiana: American hophornbeam, eastern hophornbeam, and hop-hornbeam. Despite the similarities in names, the two species are quite different in appearance. For example, while Ostrya virginiana has shaggy, peeling bark, Carpinus caroliniana has very smooth bark with wavy ridges. These two species, and many others, bear the name Ironwood because of their hard, dense wood.

The meaning of the name hop-hornbeam is broken down in several ways: "hop" refers to the similarity of the fruit clusters to hops, an ingredient in beer-making; "horn" refers to the hardness of the wood; and "beam" comes from an archaic English word for tree.

The genus name, Ostrya, may come from the Greek work ostrua, which means a tree with very hard wood, or ostruos, meaning scale, in reference to the scaly catkins. The species name, virginiana, means "from Virginia."

Commercial use

Hop-hornbeam is too small and its wood is too hard and dense for most commercial uses. However, it has been used to manufacture tool handles.

Wildlife value

The seeds, buds and catkins serve as a food source for songbirds, squirrels, pheasants, and grouse.

Similar species

Hop-hornbeam is very similar to two other species of Ostrya, Ostrya carpinifolia (European hop-hornbeam) and Ostrya japonica (Japanese hop-hornbeam). The differences are extremely minor; distinction poses a challenge even for some seasoned tree experts.

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Hop-hornbeam IN TORONTO

Hop-hornbeam's place in Toronto's urban forest

Landscape value and potential for home planting

As a fairly small tree, hop-hornbeam is suitable for planting in smaller sites. Its unusual fruit and distinctive bark make it a visually interesting addition to the urban landscape. However, it is slow-growing and it has not been a popular urban tree in the past. Due to its very large range, which extends into the southern US, hop-hornbeam is naturally associated with a wide range of broadleaf trees and such conifers as pines, firs, and hemlock.

In its native habitat, hop-hornbeam is an understory tree, so it is tolerant of some shade. It should be planted in moist, slightly acidic soil.

Pests and diseases: Hop-hornbeam is relatively free of insect pests and diseases. However, it may succumb to trunk or butt rots.

This tree is available for planting through the City of Toronto's street tree program and LEAF's backyard tree program .

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WHERE CAN I SEE Hop-hornbeam?

Links to maps at Canadian Tree Tours:

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