How to Repot Bonsai Plant

Bonsai is a Japanese art form which utilizes cultivation techniques to produce, in containers, small trees that mimic the shape and scale of full-size trees. Similar practices exist in other cultures, including the Chinese tradition of penzai or penjing from which the art originated, and the miniature living landscapes of Vietnamese Hòn non bộ. The Japanese tradition dates back over a thousand years. There are varieties of Bonsai plant offerings you can buy at the Mumbai-based online nursery Root Bridges from all over India.

To prevent a tree from being pot-bound and ultimately starving to death, regular repotting is crucial. Re-potting your Bonsai will not keep it small but will supply the tree with new nutrients that it needs to grow and flourish. 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.

Pot suitability -  Place the plant in a pot suitable for its style and size of bonsai. In round pot or square shaped pot, position the plant in the centre. 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.

Instructions to repot a bonsai:

1. Determine when your bonsai needs to be re-potted. The primary reason for re-potting a bonsai tree is when its root system begins to choke itself off. To determine whether this is happening, gently lift the entire tree from its pot. If the roots have begun circling around themselves, you need to re-pot. Eventually the roots will grow thick enough to displace all the soil within the root system, and the tree will starve.

In general, it is best to repot right before your bonsai begins growing vigorously. In most cases this is spring. However, there are exceptions to every rule, so you should consult an expert to really determine what the best re-potting season is for your bonsai.

2. Pick the right time of year for repotting your plant. Repotting should ideally be performed in early spring. At this time, the tree is not under the pressure of maintaining full foliage, and thus will be subject to less of a shock by repotting. The vigorous growth that begins in spring will also help the plant to heal any damage caused through repotting.

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.

3. Remove the old soil from the tree's roots. Once you have lifted the tree from its pot and decided to repot it, you'll need to remove as much of the old soil as possible. Knock the soil out of the root system either using your fingers or a specialized tool called a root hook. Gently disentangle the roots if they have grown thickly together.

4. Remove some of the bonsai tree's roots. After untangling the roots, prune back some of the longer ones to keep the tree from outgrowing its pot. At this point, you should also remove any roots that appear to be rotting. As a rule, avoid removing more than 25 percent of the tree's total mass of roots.

5. Reposition the tree in its pot. When the roots are trimmed, gently lower the tree back into the pot. Fill the pot to the brim with your desired potting mix. Work the soil into the root structure so that there are no air pockets remaining between the roots.
   1. A typical bonsai potting mix will consist of akadama, gravel, and compost in about a 2-1-1 ratio. Akadama is a special kind of granular clay produced especially for potting bonsai trees. You may need to adjust this ratio depending on your climate and tree species.

6. Water the bonsai tree. Watering the tree after repotting will help the soil to settle. Keep the tree protected from strong winds for a month or so after repotting.

• 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 Tips for bonsai planting.

In order to repot a small bonsai tree, knock the soil out of the root system either using your fingers or a specialized tool called a root hook. Gently disentangle the roots if they have grown thickly together. Remove some of the bonsai tree's roots. After untangling the roots, prune back some of the longer ones to keep the tree from outgrowing its pot. 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 if the container is in good condition. Prune extra roots of such plants superficially and append an additional layer of soil mixture and fertilizers.

Mudita Khanna (mudita.khanna@gmail.com) has contributed to this article.