The Korean Hornbeam, or Carpinus coreana, is a deciduous tree native to North America and Asia. Beautiful pleated foliage makes the Korean Hornbeam especially useful in group plantings as well as for specimen bonsai. The growth rate of the hornbeam species varies greatly which is of particular importance if you are growing them with the intention of having a larger trunked bonsai. Carpinus coreana is very popular because of its small leaves and intensely ramified growth pattern but keep in mind that this is a slower growing hornbeam and in general, it will take twice as long as the other species to achieve similar trunk caliper. However, being slow growing and hearty, this bonsai is a perfect specimen for beginning bonsai enthusiast because it allows time to get used to training this beautiful tree. Not only for beginners, this bonsai will be prized for all levels of bonsai mastery and is a perfect addition for any outdoor garden.
The Korean Hornbeam is cherished for its small, light green serrated leaves which have exceptional orange and yellow autumn coloring. This specimen showcases attractive folded or wrinkled foliage which gives the leaves a pleated look. The tiny pleated leaves reduce easily to less than 1 inch and it attains a zigzag twiggy character after only a year in a bonsai pot. The bark is smooth, gray and fluted. The fall color is red and orange to yellowy bronze and stands out in the in the fall because its transformation emerges in showy stripes. Brown leaves occasionally cling to the tree into the winter. Mature hornbeam specimens will produce white hop-like flower blossoms in the spring and seed pods that are an attractive addition to the fall and winter display.
The Korean Hornbeam is a deciduous tree and as such, requires a dormant period for optimal health. To achieve this, it must be kept outdoors with exceptions only being made for brief display for special occasions. It will require root protection from extremes in temperature during the winter months, as well as protection from the scorching heat of the afternoon sun when in the hottest, driest period of the year.
This bonsai, in its natural habitat, generally grow as an understory tree. This is why they require protection from the intensity of afternoon sun in hot, dry display areas. It promises to grow with an attractive open habit in total shade, and will tend to form a dense canopy in full sun.
This bonsai will thrive with moderate watering. Be sure to avoid letting the soil dry out completely. It can survive mild neglect, and as such, will allow infrequent travel as long as it isn’t during the hottest time of the year. If travel is required it is best to make arrangements for adequate care.
This bonsai will require a weekly feeding for the first month after bud-burst, switching to every two weeks until late summer. Use an organic fertilizer at half strength. Do not feed for two months after repotting.
Pruning / Training:
Your Korean Hornbeam can be wired from spring to autumn. Keep in mind that some bark protection may be needed to prevent damage, but in general, the hornbeam is fairly sturdy for a deciduous tree and will accept repeated hard pruning. Prune back to the first pair of leaves on new shoots to force back budding with the best times for minor pruning being early spring and after flowering. Major developmental pruning should be done in late winter, before bud burst. As it ages, branches do tend to die back for no discernable reason. Hornbeams make good group plantings as well as specimen bonsai due to the fine branch ramification and small leaf size in bonsai culture.
Insects / Pests:
Due to its hearty nature, relatively few insects attack hornbeam. Several fungi cause leaf spots on the Korean Hornbeam; Canker, caused by several fungi, causes infected branches to dieback and entire trees die if the trunk is infected and girdled. Severely infected trees cannot be saved and any infected branches should be pruned out. Preventing fungi is largely a matter of proper watering. Keeping an environment that is not too wet, or too dry will go a long way in promoting bonsai health.
Cuttings are the best way to propagate the Korean Hornbeam. Cutting produced plants from mature wood are capable of flowering in a year or two as opposed to seven years or more for seedlings. To obtain cuttings, take clean scissors and obtain a three inch piece for mature wood, dip in rooting hormone and place in consistently moist, good draining soil. Place in a shady area to promote root development.
You will need to repot this bonsai every 2-3 years in early spring using a basic bonsai soil. Your Korean Hornbeam prefers a deep pot and will want minimal root pruning.
Take care to keep the leaves of your bonsai free from dust to ensure proper cell development and health.