How to repot a bonsai

The repotting of a bonsai

A frequent question about bonsai care is when to transplant. The roots of all trees grow naturally to find the water and nutrients that are so necessary for life. Thus, when a tree grows in a pot, the roots grow until they occupy the entire space.

With the passage of time, the soil wears out and loses the ability to provide the nutrients that the tree needs. When watering, we will notice that the water penetrates with more difficulty in the old soil. If we lift the tree from the pot, we will see that the roots have become a thick and tangled ball. This will mark the time to start thinking about transplanting.

How to repot a bonsai

When is the right time for a bonsai repotting?

The favourable time for transplanting is usually at the end of plants’ winter slumber, just before the tree begins its growth period.

How do we have to repot?

  1. Gather everything we will need and keep it in hand: pot, tools and soil, so we don’t have to constantly interrupt the process in search of the lost tool.
  2. Lift the tree from the pot, remove the old soil by untangling the roots with the help of a kumade (small rake). We can even use the jet of water from a tap or hose.
  3. Trim about a third of the roots.
  4. Transplant the tree with new soil. We will make it penetrate well between the roots with the help of a chopstick, trying not to leave “air pockets”.
  5. Water well, until the water runs clear through the drainage holes in the bottom of the pot.

Discover the Introductory re-potting bonsai pack by clicking here.

What soil to choose when repotting your bonsai

Let’s talk about the best repotting soil for your bonsai. Bonsai live well on grainy soils like Akadama mixed with a soil that helps drainage like Terrabonsai. The proportion varies according to the species but, in principle, Akadama is poured into a layer at the bottom of the pot (50% of the capacity) to create good drainage. For the second layer we will use Terrabonsai, in which the roots will develop further.

Akadama is the best-known substrate for bonsai, either Akadama alone or mixed with other substrates (Kanuma, Terrabonsai, etc.) The properties that make Akadama such an interesting product to grow bonsai are both its good drainage (roots oxygenate better) and its resistance to degradation.

Terrabonsai is composed of blond peat, Akadama and volcanic stoneware. By mixing these different components, an optimal substrate is obtained for beginner hobbyists; the perfect combination of air and water retained by the substrate gives the possibility of not being excessively dependent on irrigation, since it retains water well.

Another substrate to consider is Kanuma (pH 4). Suitable for growing bonsai that need an acid soil, mainly azaleas (Rhododendron) and some conifers.

How often should I repot?

The frequency varies by species. In general, young bonsai grow taller than mature bonsai, and need more frequent transplantation.

The frequency of transplantation can vary greatly from fruit trees that are generally transplanted annually, to conifers that can be transplanted approximately every 4 to 6 years.

These figures are indicative since each tree must be observed individually to know when it needs to be transplanted.

Bonsai repotting aftercare

A transplant at the right time does not pose a great risk for the tree. But until the roots begin to work again, we should protect it from the wind and the direct sunlight until it begins to sprout, spraying the leaves frequently.

At Mistral Bonsai we have prepared a basic Maintenance Kit for our bonsai: fertiliser, watering can, scissors and a small work guide for bonsai. All the essentials!

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