A popular bonsai species for beginners, as it is a strong tree that responds well to pruning and can be kept both outdoors and indoors. Most attractive: fine branching, small glossy leaves and beautiful bark.
Location
To provide important and natural weather conditions and changes of seasons for the plant, cultivation is outdoors. It is possible to keep it indoors if it is cold wintered at positive temperatures for 2–3 months (heated loggia, balcony, winter garden, terrace, garage, etc.). If kept in a room, it is also necessary to provide good lighting, humidity of about 70% and fresh air.
It should be taken into account that trees after cold wintering develop better and faster than those that were wintered in warmer conditions.
In cold wintering most trees shed their leaves, in warm wintering they retain them.
Temperature regime
During the growing season, the optimum temperature is +15 to +24 degrees Celsius of heat. Elms do not like heat and dry air. During the winter dormancy period, a cool regime is needed, so the temperature is reduced to +5…+15 degrees Celsius. The critical temperature is from 0 to +4 °C.
Lighting
The required duration of daylight illumination is 10–12 hours per day. In summer can be in sun or semi-shade.
With good lighting, the internodes (distance between pairs of leaves) and the size of leaves are optimal for this species. If there is a lack of light, the shoots elongate in length and the leaves increase in size.
Good lighting should be provided regardless of the type of wintering (cold or warm). Lack of light leads to yellowing and falling leaves.
For additional lighting, it is best to use grow lights or full-spectrum LED lamps.
Soil
The recommended soil mix for elms consists of equal parts — pumice, Lava and Akadama (see here).
It is not unreasonable to add peat, biohumus, sand, compost, and perlite.
The necessary pH level is from 5 to 8.
As drainage, you can use expanded clay pebbles.
Watering
It is necessary to constantly monitor the moisture content of the soil and take measures in time so that it does not dry out — this is disastrous for the plant. Kanuma (see here) sprinkled on the surface layer of the soil can be used for visual control of moisture. Kanuma darkens when the soil is moist and lightens when it dries out. Note, however, that drying out the topsoil is only a signal to check moisture, as there may be sufficient moisture inside the container, especially on sunny and windy days.
The tree responds well to crown spraying in spring and summer.
Fertilizers
During the growing season, elms are fed with organic bonsai fertilizers in granules: Biogold, Hanagokoro (see here). The advantage of solid fertilizers is that their effect is more uniform and longer lasting.
No fertilization is necessary during the dormant period.
Transplanting
When young, Chinese elms should be replanted every two years. As they mature and increase in size, they can be transplanted at longer intervals. Regardless of age, the best time to transplant is in the spring. Repotting includes pruning the roots and renewing the soil.
Shaping and pruning
Elm grows back quite quickly and requires frequent pruning.
To limit the growth of shoots in length and to induce the growth of lateral shoots, it is possible to pinch the growing point (at the end of the shoot).
It is possible to give the necessary direction to the individual branches by stretching and supporting them.
Before pruning a shoot (up to 1–2 pairs of leaves), allow it to develop to 3–4 nodes. The best time to prune large branches is late fall.
Chinese elm is ideal for shaping with the standard wire method. Wire wrapping should be done without overlapping dormant buds.
Since the bark of this tree species is very soft, it is recommended to use aluminum wire instead of the harder copper wire.
Diseases and pests
Chinese elm is resistant to pests and diseases, but insects or spider mites occasionally appear. Both pests can be controlled with chemicals.
