Japanese Holly
(Ilex crenata)
Country of Origin : Japan and Korea
Bonsai Styles : Informal upright, cascade, broom
Zone : 6 – 8
Japanese holly, aka ‘Japanese evergreen holly‘ or ‘box-leaved holly‘, is a slow growing, long-lived tree or shrub. It is a hardy tree and indigenous to northern hemisphere.
It has glossy, dark green leaves with scalloped (not spiny) edges. Due to the thick bark, the trunks and branches of these trees tend to appear rather fleshy, but their shoots are thin.
During the summer, it produces white flowers, which are followed by black berries (in female plants).
While European hollies (Ilex aquifolium) have dark green leaves with needle-like points on the margins, the leaves of Japanese holly tree are oval, very small, and do not have any sharp points.
It is ironic that one of the Japanese common names for this variety is ‘English Holly‘, just to make matters more confusing.
Important : European holly tree doesn’t make a good bonsai subject because the leaves are stout and thick, and it produces stout shoots rather than fine woody twigs. Japanese holly bonsai is a better choice.
Furthermore, there is another Japanese holly bonsai variety called Ilex serrata. Even though this variety is also called as Japanese holly tree, it is completely different from Ilex crenata. Ilex serrata is deciduous and Ilex crenata is evergreen. Also, both of them are very different in appearance. (Important piece of information to have when making a bonsai purchase)
Read more : Japanese deciduous holly bonsai tree (Ilex serrata)
Varieties of Ilex crenata used for making a Japanese holly bonsai tree :
- Ilex crenata ‘Convexa’ : A compact version of Japanese holly with convex glossy leaves.
- Ilex crenata ‘Stokes’ : This is a compact dwarf variety of Japanese holly and has tiny leaves.
Japanese holly bonsai tree makes a good indoor bonsai tree, provided it is placed in a cool location.
Best location to keep Japanese Holly Bonsai
The Japanese holly bonsai is one of the very few species that can be grown both indoors and outdoors, in the sun or in the shade.
Japanese holly bonsai trees are typically considered indoor bonsai trees because of their shade tolerance.
During the summer, plants will benefit from a spell outside if placed in a bright location, such as on a windowsill.
However, if you keep the bonsai tree in the sun, make sure that the roots don’t dry out. Furthermore, when exposed to too much sun, Japanese holly bonsai tree will have a slower growth and smaller leaves.
In winter, move the bonsai pot to a cool unheated room (a warm or heated room is not necessary).
A temperature range of 30-90°F (-1 to 32°C) is advisable for growing Japanese holly bonsai tree.
Place the tree in shade during summer and acclimatize it to the sun in early fall to increase its fall color.
Refer sunlight requirements for indoor plants for more indoor gardening ideas. Also, refer to do bonsai trees need sunlight for more indoor and outdoor bonsai location ideas.
Propagation of Japanese Holly
Japanese holly tree can be propagated by stem cuttings.
Spring or summer is the best time to take softwood cuttings.
For propagating fruiting Japanese holly trees, use cuttings from female tree.
Watering Japanese Holly Bonsai
In the summer, give it plenty of water.
In the case of female Japanese holly bonsai, increase watering at the time of flowering. This will help in the development of berries.
Water the compost only when the surface has dried a little.
Spray some mist on the foliage, especially when the bonsai is placed in a dry room.
Reduce watering frequency in the winter season.
Wiring Japanese Holly Bonsai
Spring is a good time to do wiring if necessary.
If the stems are brittle, wrap them in raffia to protect them. Also, the bark of the tree is quite fleshy and thick. This increases the chances of scarring. Hence, be careful while wiring.
One trick you can use while wiring is, wire the plant when the bonsai soil is a little dry. At this time it is relatively easier to bend the branches and damaging the bark is less likely.
The wiring should be left on for almost two years so that the branches can set (because of slow growth rate of the tree).
Keep an eye on the bark regularly to make sure it’s not scarred by the wire as it grows (especially at the top of the tree). In the event that the wire appears too tight, remove it and reapply, coiling the wire in the opposite direction.
Pruning Japanese Holly Bonsai
When to prune Japanese Holly bonsai?
How to prune Japanese Holly bonsai?
Japanese holly bonsai can be pruned in fall or early spring.
Prune back the new growth to maintain the desired bonsai style and shape.
Don’t prune away the shoots that bear the flowers in summer if you want berries to form.
Much like a ‘topiary‘, clip young bonsai specimens constantly to create and maintain a neat shape.
Afterwards, prune new sprouts back to two to three leaves, and remove surplus branches.
Pruning in fall will keep the bonsai tree frost free in winter.
Hollow the pruning wounds to prevent the tree from having unsightly swellings of healing tissue.
Hard pruning in summer will induce vigorous growth on weak branches.
Pinching Japanese Holly Bonsai
To maintain the desired shape of your Japanese holly bonsai tree, pinch out the growing tips of new shoots as needed in the growing season.
In female Japanese holly bonsai tree, once flowering is over, pinch out the growing tips.
Repotting Japanese Holly Bonsai
When to repot Japanese Holly bonsai?
Japanese holly bonsai tree can be repotted every two years during late spring.
Use a free draining, moisture retentive bonsai soil mix.
OR
Use a mix of 60% organic matter and 40% grit.
OR
You can also use a bonsai soil which is a mix of leaf mold and loam in the ratio of 1:1. Add a little bit of sharp sand to this mix if you can.
Important : High pH soil will lead to yellowing of leaves.
Must Read: Bonsai Soil Recipes
Must read : Choosing the right bonsai container
Feeding Japanese Holly Bonsai
Apply a balanced feed throughout the growing season.
Change this to nitrogen free feed in fall.
Diseases and pest of Japanese Holly Bonsai
Typically, Japanese holly bonsai trees are pest free.
However, they can be sometimes attacked by leaf miner, spider mites, aphids and whitefly. Apply a systemic insecticide if you can not remove them by hands or jet of water.
Japanese Holly bonsai care
Japanese holly bonsai trees are mostly trouble free bonsai trees. However, certain basic precautions must be taken so that the tree is healthy and in shape.
Over watering will cause root rot.
Bonsai grown outdoors need frost protection for their roots in winter (even mild frost), and their foliage needs protection from freezing winds.
Frost will not damage the foliage and twigs, but the thick, fleshy roots will burst when the water in them expands as it freezes.
To overwinter your Japanese holly bonsai tree if you cannot find a suitable shed or room, you can keep it on a low platform in a sheltered corner of your yard. The bonsai container should be insulated with multiple layers of glass fiber fleece or Styrofoam.
Japanese hollies blossom easily, but their flowers are small and greenish-white, making them hard to spot. Female and male flowers grow on separate plants. Berries will only set on female plants, provided they have been fertilized by the nearby male.
What to look for when buying Japanese Holly Bonsai
Often, when you go to a nursery to purchase a Japanese holly bonsai specimen, you might find an attractive bonsai specimen covered with berries. Don’t be under the impression that it will produce berries the next year also. Keep in mind that it will only produce berries if it is fertilized by a nearby male plant.
Avoid bonsai specimens with heavy branches. Heavy branches are nearly impossible to reshape. Look for a bonsai that has evenly distributed branches and the thickness of the branches should be proportionate to the thickness of the trunk.
Avoid bonsai with unsightly pruning scars and wire marks. As these will take a long time to heal.
If you are lucky, you might find a Japanese holly bonsai specimen with a thick root system which has intriguing and striking surface formations. Such specimen is a good purchase.
