In bonsai gardening, re-potting is the beginning of presenting a plant in a special form. The plant is placed specialized bonsai pot, which is a shallow ceramic container with two distinct drainage holes at the bottom. Re-potting in bonsai is always done in association with root pruning, and complete or partial modification of soil mixtures.
Repotting a bonsai plant may involve following situations:
Removal of a small tree from an ordinary pot and replacing it in a bonsai pot.
Removal of a small tree from the ground and placing it in a bonsai pot.
Removal of a plant from a bonsai pot and placing it in a same ornamental bonsai pot after maintenance.
Removal of a plant from an old bonsai pot and replacing it in a new bonsai pot.
Placing the plant in bonsai pot:
Place the plant in a pot suitable for its style and size of bonsai. In round potor square shaped pot, position the plant in the center. In an oval or rectangular pot, place the plant at one-third of the container's length from any end. The plant may be placed at right or left end of the pot, depending upon individual liking.
General guidelines for re-potting bonsai plant:
Clean the new bonsai pot and place fine plastic or wire mesh preferably copper wire mesh on the drainage holes. Spread some soil over mesh and level it.
Insert two ends of a piece of copper wire through the outer sides of bottom holes.
Take the tree out from the old pot/ ordinary pot/ ground. Remove the upper and side layers of soil from the root ball.
Root pruning: Taproot may be cut up to two-third of its length along with some fibrous roots. When the plant is taken out of old bonsai pot, cut all exposed roots.
Place the plant in the container, tie with wire, keep its base visible above the level of the pot.
Now fill the pot with soil mixture. To achieve an attractive profile, compress and shape the soil lightly. Raise the upper surface of the soil so the plant appears to grow in a mound of soil.
Moss may be used as ground cover. This enhances look, checks evaporations and at the same time helps to prevent soil from being washed out at the time of watering.
The first watering after re-potting should be done either through misting or by placing the pot in a water tray; allow water to enter through bottom hole slowly rise to the top. Read about the art of making bonsai.
When to re-pot bonsai plants?
Best time for re-potting bonsai is early spring (Jan-Feb) or monsoon (June-July), even though it can be done at any time avoiding the hot summer days. Frequency of re-potting depends on the plant and its root growth. Evergreens like pines and Junipers require re-potting only after three to five years, while flowering and fruiting trees may need re-potting every year.
Note: Frequency of repotting is more in younger plants as the trees are still growing and attaining the desired shape and size. A well developed, 20-25-year-old bonsai tree need not be re-potted as long as the container is in good condition. Prune extra roots of such plants superficially and append an additional layer of soil mixture. Read more about ‘The magical bonsai trees’.