The rather slow growth of the Japanese maple allows it to be grown in pots without any problem. However, after a few years, it will need to be repotted in good conditions to continue to give its best.
When to repot the Japanese maple?
The best time to repot the Japanese maple is in early spring before budburst, or in the fall after leaf fall.
There are many varieties of Japanese maple, some of which are better suited to pot cultivation than others because they keep a compact habit. This is the case of Acer palmatum 'Corallinum' which has bright pink leaves in spring, turning pale green and then wine red in autumn, of 'Dissectum' and its numerous cultivars which rarely exceed 2 meters in height but have flamboyant foliage, and of 'Ukigumo' marbled with white and pink. These varieties grow slowly and are well suited to pot culture. They can be repotted only every 4 years. The other years a surfacing in spring will be enough, if the pot is big enough.
How to repot the Japanese maple?
Gently remove the root ball from the pot by pulling on the trunk. If the plant does not come out the first time, tap the sides of the pot. If it is made of plastic, do not hesitate to sacrifice the container by cutting it with a cutter if necessary.
If your tree is installed in a beautiful ceramic pot and is difficult to remove, slide the blade of a knife between the root ball and the wall to loosen the roots. Proceed with care.
Once the root ball is out, tap it to remove as much soil as possible.
Immerse the root ball of the maple tree in non-limestone water at room temperature for at least ¼ hour. The tree will hydrate.
Then check the health of the roots and prune those that are dead or damaged with disinfected secateurs.
Choose a larger pot than the previous one, with a hole in the bottom, because this tree does not tolerate stagnant humidity at the roots. For the same reason, leave a layer of clay balls at the bottom of the pot equivalent to 20% of its volume.
Prepare a mixture composed of 1/3 vermiculite, 1/3 small pine bark and 1/3 very good potting soil or better still homemade oak leaf compost. The mixture should have an acidic pH. Add a handful of ground horn and dried blood to make it richer.
Plant your tree upright in the pot containing this substrate. The neck of the tree will be located 2 to 3 cm below the top of the pot.
Pack and water thoroughly.
Add more mixture if necessary and mulch with pine needles or bark. This mulching will maintain a good humidity to the substrate while slightly acidifying it.
After repotting the Japanese maple
Place your tree in a location sheltered from strong winds and full sun.
It will do well in semi-shade in a courtyard, a patio or on a terrace sheltered by large walls. In the garden, reserve a place protected by other trees or hedges to protect it from the wind.
Water often, especially in summer. The mixture should never dry out completely between two waterings. Do not let water stand in the saucer.
Scratch a mixture of compost and shredded horn each spring at the base of the tree, then replace the mulch.
