[GLBS] Botanical Perspectives - Native Hornbeams and Hop-Hornbeams

Bonsai News

by Ross Clark*


Hornbeams (in the genus Carpinus) and hop-hornbeams (in the genus Ostrya) are close relatives of the birches.* They are medium-sized trees with alternate and doubly toothed (technically, doubly serrate) leaves, similar to the leaves of birches.* Carpinus and Ostrya have elongated cone-like fruit clusters that become obvious in summer.* The fruit clusters of hop-hornbeams strongly resemble the fruits of hop plants (which put the bite into beer).* Most of the common names of Carpinus and Ostrya are confusing because they vary in different regions of North America.* However, "hornbeams" for Carpinus and "hop-hornbeams" for Ostrya are universal common names that are not easily confused by people.


Hornbeams have been popular as bonsai subjects for some time, but hop-hornbeams seem still to be in the process of being discovered as bonsai subjects.* Various species of hornbeams and hop-hornbeams are native in the Northern Hemisphere.**


Mature hornbeams have smoothish gray bark, similar to the bark of beeches.* "Blue beech" is one of the common names of American hornbeam.* Mature trunks and branches have a longitudinally or ridged appearance, which relates to another common name, "muscle-wood."* Since fruits are necessary for accurate identification, hornbeams often are misidentified, so it sometimes is difficult to know what species you’re dealing with.* (Some nurseries and growers offer species which actually do not exist.)* Since European hornbeam (Carpinus betulus) is widespread in Europe, it is the species most often used for bonsai there.* In the U.S., C. turczaninovii and C. coreana from eastern Asia (which may not be distinct species), are increasingly imported and propagated for bonsai, and Japanese hornbeam C. japonica) occasionally is used.* Our native American hornbeam, Carpinus caroliniana, should be more widely used for bonsai.* There are additional minor species which are rarely cultivated.


American hornbeam (Carpinus caroliniana) is native over most of eastern North America, northward into southern Ontario.* It grows in forested habitats where the soil does not dry out.* Hornbeams live naturally where soil moisture is never limiting; they are especially frequent in floodplain forests and along streams, where they often lean out over streambanks into full sunlight.* Since all hornbeam species are adapted to understory conditions (i.e., under other trees), for best results hornbeam bonsai should be grown in partial shade.* They will survive in full sun when well supplied with water, but the leaves usually will bleach under high light intensity, and the root system will be under much greater stress.* Carpinus caroliniana has undistinguished fall color; its leaves simply remain green or briefly turn yellow before dropping.* European hornbeam (C. betulus) tolerates full sun better and its fall foliage has a longer lasting yellow color.* The most natural bonsai styles for hornbeams are informal or slanting, without "Chinese-style" twists in their trunks.* In nature, hornbeams are almost single-trunked, although several trunks and groves also are workable bonsai styles for hornbeams.* By the way, a named variety of our native hornbeam, C. caroliniana var. virginiana, is not really distinct from the species, so the varietal name should not be used.


Hop-hornbeams (the genus Ostrya) are as widely distributed as horn-beams, but there are not as many widespread species.* Ostrya carpinifolia (European or Italian hop-hornbeam) is the species most often used for bonsai in Europe.* There are several little-known Chinese species.* Our native eastern hop-hornbeam (Ostrya virginiana) has a geographic range similar to that of American hornbeam, but its range extends farther west and north.* There are outlying populations westward along the Missouri River and in the South Dakota Black Hills.* Plants originating from those outlying populations should be especially tough and tolerant of environmental extremes.* There is a second species in the southwestern U.S. (O. knowltonii), but it usually occurs in isolated populations and should not be collected because of its rarity.


Eastern hop-hornbeam is easy to distinguish because its mature bark is light brown and peels off in small pieces.* Its leaf surfaces are soft and downy to the touch, and from a distance, its fruit clusters are dead ringers for the fruits of hops.* Hop-hornbeam occurs as a medium-sized understory tree or out in the open in upland, well-drained habitats.* It is especially frequent on bluffs and steep slopes above large streams.* It sometimes is common in old, rocky pastures, severely cut-over upland forest, and even along fence lines–in other words, easy collecting territory.* It is much more tolerant of dry soil and full sun than American hornbeam, although its leaves do bleach in full sun.* An informal, single-trunked style is closest to how hop-hornbeam grows as a wild plant.* When grown in full sun, its fall foliage is an outstanding golden color.


Native hornbeams and hop-hornbeams should be much more widely used as bonsai.* They are native, well-adapted to our climate, and occur throughout our region.* No matter where you live in the Midwest, hornbeams and hop-hornbeams are not far away.* They are excellent bonsai subjects, and you cannot get any cheaper than free!* Incidentally, eastern hop-hornbeam should be used more often in home landscapes.


Beware the Cicadas
Finally, here is a bit of miscellaneous information not directly related to hornbeams or hop-hornbeams.* Some people who read this may be approaching the time when periodic cicadas will emerge by the millions.* After they mate, female cicadas lay their eggs by cutting deep slits into twigs with their sharp ovipositor, and depositing their eggs directly into the wood of the twig.* The twig dies and falls to the ground, and the newly-hatched cicada larvae or grubs burrow into the ground.* Please be advised that cicadas will lay eggs into the branches of bonsai, which can cause considerable damage.* So, if you live in "cicada country" and hear the whirring call of a massing cicada population, you might be advised to take protective action.* What would that action be?* I don’t know.* Hire a guard with a fly swatter?* Maybe use nasty insecticides?* I have experienced the damage, but not discovered the remedy.* Maybe someone who reads this knows a reliable remedy.




http://www.louisvillebonsai.org/pos...-Hornbeams.aspx

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