Why Repot?

Plants do not eat food; they absorb and create it from their habitat. In order to live, plants need water, carbon dioxide and sunlight.

These are required for photosynthesis, the means by which plants create carbohydrates (starch and sugars) in their leaves. Carbohydrates are burned in a process called respiration; this drives cell division and plant growth. Respiration needs oxygen and the process creates carbon dioxide and water as by products.

If insufficient oxygen is available, the process produces alcohol, which is toxic to the tree. Oxygen is readily available above ground but it is harder to acquire within the soil around the roots this is one reason why repotting is so necessary to your tree’s survival.


Signs that a Bonsai Needs Repotting

There are no absolute rules for this, so you must use a good share of common sense.   More often than not, the trigger for repotting will be when you want the tree to grow larger and you need a bigger pot or when you find a pot more to your liking or more suitable.   With these exceptions, the general rule for repotting is between one to five years, depending on the species of tree and the size of the container/pot.   Fast growing trees need to be repotted every year or every other year.  More mature trees need to be repotted every three to five years. Any of the following are a sign that the tree needs repotting:

  • The tree is pushing upwards out of the pot.
  • The soil will not absorb water and it just runs off the surface. This means the soil has compacted and that the tree is pot-bound.
  • A slowing of growth compared with last year.
  • Reduced uptake of water in summer.
  • Rapidly reducing leaf size and colour.
  • Early leaf drop in autumn.
  • Yellowing of foliage colour.
  • Dieback of fine twiggery (the small, delicate parts of the branches) in winter.
  • Liverwort and algal slime forming on the soil surface. Sign of too much surface water not draining properly.
  • Leaf drop in summer.


The tree below needs repotting. The root system is too tangled and extensive for the size of the tree.

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