Hornbeam - Carpinus
General Information: A handsome tree in many locations, the tree slowly reaches a
height and spread of 20 to 30 feet. It will grow with an attractive open
habit in total shade, but be dense in full sun. The muscle-like bark is
smooth, gray and fluted. Ironwood has a slow growth rate and is
reportedly difficult to transplant from a field nursery (although
10-inch-diameter trees were moved with a 90-inch tree spade during the
winter in USDA hardiness zone 8b with no problem) but is easy from
containers. The fall color is faintly orange to yellow and stands out in
the landscape or woods in the fall. Brown leaves occasionally hang on
the tree into the winter.
shade in summer, otherwise full sun.
increasing in summer. Never let the soil dry completely.
instructions vary greatly. Simon and Schuster's Guide recommends feeding
Every 20-30 days, stopping for a month-long break in midsummer. The
advice to stop feeding in July-August is echoed by the Samsons.
Tomlinson is far more aggressive, recommending a weekly feeding for the
first month after bud-burst, switching to every two weeks until late
summer. Ordinary plant food at half strength is fine, as is bonsai
fertilizer. Of course, the whole controversy can be avoided with
time-released pellets. Do not feed for two months after repotting. C.
laxiflora may experience branch die-back if underfed.
Pruning and wiring:
Elliptical, heavily veined leaves with pointed tip. Can be wired from
spring to autumn - some bark protection may be needed, but the hornbeam
is fairly sturdy for a deciduous tree. Accepts repeated pruning, quickly
healing scars. Prune back to the first pair of leaves on new shoots. The
best times for minor pruning are early spring and after flowering. Major
developmental pruning should be done in late winter, before bud burst.
Strong apical growth of upper part of tree, so it may be necessary to
cut back radically at the apex, but to prune the lower portions of the
tree conservatively, especially with the Japanese species, to check its
rapid apical growth. Defoliation to reduce leaf size is possible, but
will inhibit flowering and fruiting. As it ages branches die,
complicating management as a bonsai. As the tree ages, branches may die
back for no discernable reason.
seed. Fresh seed in fall is best - sow immediately. Otherwise, seed must
be cold treated and planted in late winter. Seed which has been dried
may need up to a year to germinate. Murata warns that it is difficult to
get viable seed from C. japonica, as there is little overlap in
flowering time between the male and female flowers. May also be
propagated by cuttings and air layering in spring.
Repotting: Every 2-3
years in early spring. Use basic bonsai soil. Prefers a deep
Pests and diseases: Pests: Relatively few insects attack hornbeam. Maple phenacoccus
forms white cottony masses on the undersides of the leaves. Diseases:
None are normally very serious. Several fungi cause leaf spots on
Carpinus. Leaf spots are not serious so control measures are usually not
needed. Canker, caused by several fungi, causes infected branches to
dieback and entire trees die if the trunk is infected and girdled.
Severely infected trees can not be saved and infected branches are
pruned out. This could limit usefulness in parts of the Deep
Some species suitable for bonsai:
- Carpinus betulus: hornbeam, European hornbeam,
European ironwood. Can grow to 50 ft., but is usually shorter. It has
4 inch leaves and catkins, and drooping clusters of fruit. Its autumn
color is yellow-green, and it has grey bark. Hardy in zones
- Carpinus caroliniana (C. americana):
American hornbeam, blue beech, water beech - Native to eastern North
America. A small - under 20 ft. - tree with a rounded habit and
generally prone to multiple trunks. Tolerates both wet soil and shade,
but does not like to be transplanted. Nice orange and yellow autumn
show. Hardy in zones 3-8.
- Carpinus coreana: Korean hornbeam - Has very
twiggy branching and a spectacular fall display with leaves that turn
yellow, orange and red, sometimes in bands on the same leaf!
- Carpinus japonica: Japanese hornbeam, Japanese
carpinus - nice flowers in spring. Smooth pink-grey bark.
- Carpinus laxiflora: Japanese hornbeam, Japanese
loose-flowered hornbeam, Loose-flowered hornbeam - smooth, grey-beige
trunk, small, glossy leaves.
- Carpinus tschonoskii: Yedoensis hornbeam, Yeddo
hornbeam Carpinus turkzaninowii: Korean hornbeam, Turkish hornbeam -
yet another hornbeam reputed to have a wonderful fall display. Has
very small leaves.
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