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Hornbeam - Carpinus sp.
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.
Family:
Betulaceae
Lighting:
Partial shade in summer, otherwise full sun.
Temperature:
Fairly cold hardy - zones 3 through 9A.
Watering:
Moderate, increasing in summer. Never let the soil dry completely.
Feeding:
Feeding 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.
Propagation:
From 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 pot.
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 South.
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 5-7.
- 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.
Bibliograhy:
"The Hearst Garden Guide to Trees"
by William Thomas (ed.)
"American Nature Guides: Trees" by Alan Mitchell
"Bonsai" by Susan M. B. Resnick
Simon and Schuster Guide
"The Creative Art of Bonsai," by Isabelle and Remy
Samson
Gordon Owen's "Bonsai Identifier"
Harry Tomlinson's "Complete Book of Bonsai"
"Four Seasons of Bonsai," by Kyuzo Murata
Florida Bonsai XIV:2: pg. 38-50.
USDA Fact Sheet ST-120
- Compiled by Sabrina Caine
Edited by Thomas L. Zane
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