Zelkova (Chinese elm) bonsai care

The Zelkova (Chinese elm) can be kept both indoors and outdoors Indoors, it does best in a very bright spot, preferably near a window where it receives plenty of daylight. Outdoors, it can be placed in either full sun or partial shade. Sufficient light helps promote compact growth and smaller leaves.

Not every Chinese elm does equally well indoors. If the tree regularly drops leaves indoors, grows weakly, or produces few new shoots, we recommend placing it outdoors. Outdoors, the tree generally receives more light, natural air circulation, and greater temperature fluctuations, which can benefit its growth.

A tree that has been indoors for an extended period must gradually acclimatize to outdoor conditions. Therefore, do not move it directly from indoors into bright afternoon sun; instead, start in a bright, sheltered spot and gradually increase the amount of direct sunlight.

In winter, the right location depends on the tree's origin and how it was grown. Some Chinese elms tolerate frost reasonably well, while specimens from warmer regions or trees that have been kept indoors for a long time may be more sensitive to low temperatures.

The Chinese elm needs regular watering, but there is no reliable fixed number of waterings per week. Temperature, sunlight, wind, pot size, and substrate have too much influence.

Therefore, check the soil daily. As soon as the top layer begins to dry out slightly, water again. Never let the entire root ball dry out completely. At the same time, the tree should not be left standing permanently in waterlogged soil.

Water generously each time, so that the soil around the roots becomes wet as well. The water requirement can increase significantly, especially on hot summer days. Check how it is doing daily during that time.

A watering can with a fine rose is useful because it prevents the substrate from being washed out of the pot.

Fertilize the Chinese elm during the active growing season, roughly from spring through autumn. The species does not require a particularly specialized fertilizer and responds well to a balanced bonsai fertilizer.

A solid or liquid fertilizer can both be used as a base. If desired, this can be combined with bonsai elixir.

An exact number of fertilizations per month cannot be established in general, as this depends on the product chosen. Therefore, follow the dosage and frequency specified for the bonsai fertilizer used.

When the tree overwinters in cool conditions and is clearly dormant, it should not be fertilized or only very lightly.

Zelkova responds particularly well to pruning and readily regrows, even from older wood. This makes it highly suitable for developing a fine and compact branch structure.

For maintenance pruning, young shoots can first develop a few internodes. Let new twigs grow to about three or four leaves before pruning them back to one or two leaves.

This process can be repeated regularly during the growing season. This makes the branching increasingly finer.

Larger structural branches are best removed when the tree is not in the middle of its strongest growth period. We recommend doing this in autumn or spring.

For thin shoots, use a sharp bonsai scissors. For thicker branches, a pair of pliers can be useful, as this allows you to make a smaller and neater pruning wound.

The Zelkova can be shaped well with bonsai wire. Both wiring and guy wires can be used to bring branches into the desired position.

Aluminum bonsai wire is usually the easiest to use for young and medium-sized branches. Apply the wire evenly around the branch, then carefully bend the branch into position.

The tree grows relatively quickly, so wire can easily cut into the bark. Therefore, check wired branches regularly during the growing season.

Spring through autumn is the suitable period for wiring. With fast-growing trees, branches should be checked especially frequently in spring and summer.

Young Zelkova (Chinese elms) are generally repotted about every two years. Older, larger, and slow-growing specimens need to be repotted less often.

The best time is early spring, around the time the tree starts to produce new growth again.

Also check the root ball. Repotting becomes important when the pot is almost completely filled with roots, water increasingly struggles to penetrate the substrate, or the roots are growing densely around the inside of the pot.

During repotting, the root ball can be combed out, and excessively long or unwanted roots can be pruned back. Chinese elms can produce many tangled, intertwined roots. Therefore, work carefully if you want to develop a beautiful, even nebari, or root base.

After repotting, use a well-draining bonsai substrate.

The Chinese elm has no exceptional soil requirements, but good drainage is essential. An airy bonsai substrate prevents the roots from being left without oxygen in wet soil for extended periods.

We recommend the following:

• 100% Akadama
• 80% Akadama + 20% Pumice (pumice stone)

The most important thing is that the mixture can retain water while also draining excess water quickly.

A coarser, highly draining substrate usually means you need to water more often. A finer or more organic mixture retains moisture for longer.

A Zelkova (Chinese elm) can overwinter outdoors in the Netherlands and more southern countries. In Scandinavian countries, the Chinese elm needs more protection if you choose to keep the bonsai outdoors.

A tree grown outdoors can remain outside during a mild winter, but the root ball in a small bonsai pot is much more sensitive to prolonged or severe frost than a tree planted in the ground.

Therefore, protect the pot during severe frost, for example by placing it in a sheltered location or in an unheated but frost-free space. Keep the tree cool; a heated living room is usually not a suitable place for a tree that is dormant in winter.

The tree may lose its leaves during a cold winter. This is not automatically a problem: it may sprout again in spring.

The Chinese elm is generally a hardy species. An important advantage is that Ulmus parvifolia is relatively resistant to the notorious Dutch elm disease, which affects many other elm species.

With bonsai, the most common pests are spider mites and aphids . Problems with these pests are mainly caused by low humidity. Therefore, regularly check both the upper and lower surfaces of the leaves. Spider mites may become visible as very fine webbing, pale spots on leaves, or slowly fading foliage. Aphids are usually directly visible on young shoots and leaves.

With a light infestation, the pests can first be removed mechanically and the tree can be thoroughly rinsed. With a severe infestation, a pesticide suitable for bonsai and the pest in question may be necessary.

Please note! Lime sulfur/Jin Seal and certain synthetic pesticides can cause leaf drop in Chinese elms. Therefore, only use pesticides when you are sure they are suitable for the intended application.

Other possible problems with Chinese elms include leaf spots, root problems, and infestations that develop when the tree remains too wet or weakened for a prolonged period.