Japanese elm
(Ulmus davidiana var. japonica)
Country of Origin : Japan
Bonsai Styles : Informal upright, broom, group
Zone : 6 – 8
Japanese elm bonsai, also known as ‘gray bark elm’, makes an ideal bonsai because of many characteristics. It is a deciduous tree which grows strong with its long erect branches. The branches emerge from a short straight trunk.
The trunk is cylindrical and straight. And the erect branches spread out and divide uniformly in all directions.
This tree’s natural growth habit gives it the appearance of a classic tree. Hence, it is mostly grown in broom style (Hokidachi) with a thick mass of foliage on the top forming a dome-shaped silhouette. Moreover, because of its natural look, it looks stunning in multi-trunk bonsai style as well.
The foliage of this tree is narrow, serrated, dark green, and becomes yellow-orange, bronze or crimson in the fall. In addition to a great fall display of colored foliage, when it is leafless, the bonsai also makes a great winter display.
It has a smooth gray bark that peels away to reveal orange tissue underneath. Throughout its lifespan, the bark remains smooth and relatively featureless.
Chinese also have their own variety of elm to make bonsai – Chinese elm bonsai tree.
Best location to keep Japanese elm Bonsai
Japanese elm Bonsai can thrive in full sun. However, if exposed to very hot sun, the leaves will scorch or turn yellow in color. Provide shade when the temperature rises above 86°F (30°C).
In very hot weather, move the bonsai container to a shaded location. You can return it back again to full sun in late summer or early fall. This practice will also improve the foliage color in fall.
The foliage will hold its spring color even in summer, if you keep your bonsai in partial shade condition throughout the year.
Although the roots of the tree can withstand freezing, the delicate fine twigs are likely to die.
Protect the bonsai from cold winds in winter.
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 elm
Japanese elm tree can be propagated by using cuttings or air-layering in summer.
They can also be propagated by sowing seeds in early spring or late winter.
Watering Japanese elm Bonsai
Water the tree throughout the growing season.
The frequency of watering is higher in summer than in fall and spring.
Keep the soil moist in winter. If the soil is left to dry, the leaves of the tree will wilt and die.
Keep foliage fresh by spraying every time you water. Keep the trunk of the tree free of algae by spraying.
Read watering bonsai tree for more details.
Wiring Japanese elm Bonsai
Pruning is the primary method used to shape Japanese elm bonsai trees. However, wiring branches that need special training can be done during the spring or fall.
Pruning Japanese elm Bonsai
When to prune Japanese elm bonsai?
How to prune Japanese elm bonsai?
In early spring, prune unwanted branches two weeks before repotting.
Pruning weak branches hard in midsummer and allowing new shoots to grow freely until fall will strengthen them. This is also a good time to remove any crossing branches which are overlapping a branch.
Japanese elm benefits from partial or hard leaf pruning in early summer. This will not only encourage strong growth, but also increase the sunlight exposure into the tree.
Pinching Japanese elm Bonsai
All throughout the growing season, once two or three leaves emerge on new shoots, pinch out the growing tips.
Also, get rid of large leaves during the growing season.
Repotting Japanese elm Bonsai
When to repot Japanese elm bonsai?
Young Japanese elm bonsai tree can be repotted every year in early spring. However, when the tree matures and becomes almost 10 years old, you can report the tree every 2-3 year (depending on the root development and whether the roots are pot bound or not).
Take notice of how the root buttress forms at the base of the trunk and prune off any crossing or unattractive roots.
The most appropriate soil for Japanese elm bonsai is moisture-retentive yet free-draining.
You can use a free-draining, bonsai soil mix or Akadama.
OR
You can also use a soil mix consisting of 40% grit and 60% organic matter.
OR
You can also make a bonsai mix with loam, peat (or compost) and sharp sand in the ratio 1:1:1. You can also mix loam and sharp sand in the ratio of 2:1.
Must Read: Bonsai Soil Recipes
Must read : Choosing the right bonsai container
Feeding Japanese elm Bonsai
The Japanese elm does not need to be overfed. Over feeding will result in coarse growth and a ruined fine network of branches.
From spring until late summer, apply a balanced feed. This should be followed by nitrogen-free feed until the leaves change color.
Read more about applying fertilizer to bonsai in bonsai fertilizer and its application.
Diseases and pest of Japanese elm Bonsai
Japanese elm trees are susceptible to scale insect and aphid infestations, which can best be treated with systemic insecticides if manual removal is not practical.
It is also possible to see caterpillars occasionally. These can be taken care of by hand. Keep the bonsai in a clean, hygienic place.
Japanese elm bonsai care
Japanese elm produces a lot of shoots. This results in congested foliage, especially at the top of the canopy.
The lack of light created by the congested foliage will result in die-back of fine twigs. Practicing a routine pruning regime is mandatory.
It is not uncommon for branches of this species to die back in the winter. Early in the spring, remove dead twigs and cut them back to healthy tissue.
Japanese elm bonsai trees range in size from almost a meter high to as small as the palm of your hand. When creating your bonsai, you should limit bonsai branches to three from the top of the trunk. A larger tree can have five branches.
You should prune hard back to the old wood every few years, so the tree can regenerate and stay proportionate.
Occasionally, groups of young Japanese elms are planted together in group style. This is done when the trunks of the trees are not straight enough.
Due to the fact that Japanese elm trees are generally propagated from seeds, they are each slightly different. In spring, some trees will leaf out before others. The leaves on some have a reddish tinted edge, while others will have bright green leaves. Fall foliage on some trees turns yellow, while on others it turns orange.
These trees planted together in a forest style bonsai create a stunning sight.
What to look for when buying Japanese elm Bonsai
The Japanese elm is generally grown as a bonsai in broom style. Although not difficult, it takes time. Hence, you will generally see bonsai specimens which are semi trained. Look for a bonsai with a basic neat branch and trunk structure. Yon can always work from a good foundation and create a good bonsai.
Look for an example with evenly spreading root structure. Make sure that the trunk is straight. (unless you are planning for group planting).
Also, confirm that the branches are emerging from the top from a common point and are spreading in all directions (not just in one direction).
Plants with week roots will wobble when shaken slightly. Avoid that and look for a plant which is holding firmly to the soil.