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Repotting

By Graham la Foy

To repot or not to repot is often a question heard among enthusiasts. Not long ago I heard the question "when last did you repot this tree?" pop up at a demonstration meeting where a very fine specimen was being worked on. The rather cynical answer suggested Why look for trouble! Does it look like it needs repotting?

Indeed, it may well seem absurd and no doubt many of the readers are acquainted with the wherewithal of the subject; but I will attempt to answer the three questions associated with repotting: why, when and how.

WHY

Firstly, the maintenance of the tree below the surface is as important as that part which is visible to the eye. It is much easier to take corrective action when say a branch requires rewiring or pruning than to notice the roots gasping for air. Common sense will suggest that if a tree is flourishing well, growing vigorously especially a young bonsai in training, then an equal amount of activity is taking place in the soil. For this tree, repotting is required sooner rather than later! The reasons why are:

  1. Roots grow in a balanced environment of air, water and soil. As the roots increase this balance is disturbed - eventually the air is diminished and the tree suffers.
  2. As the roots grow and increase in number, so the soil is broken down and its ability to retain moisture diminishes airflow is thus also hindered.
  3. To examine the roots and soil for pests. These harmful creatures lurk around and unless action is taken in time they will destroy the tree.
  4. Having done this chore will give you peace of mind that all is well with that portion of your bonsai that is out of sight!

WHEN

The second question is when to repot. It is generally agreed that during winter when the tree is dormant is not a good time to repot. On the other hand, early spring is considered the best time. The frequency of repotting depends upon:

  1. the age of the specimen - the younger the more frequent, every year or every two years; whereas for older trees, every two to five years.
  2. the type of tree, e.g. pines and junipers every year or every two years and deciduous trees need repotting annually.

The above are rough guidelines and experience will play a significant role in making intelligent decisions.

HOW

  1. Carefully remove the tree from the pot; it is recommended that you allow the soil to dry out a bit so that it is not soggy.
  2. Remove the soil using a root hook and be careful not to damage the fine root hairs. Cut off about two thirds of the root mass. The raking action should radiate away from the trunk and the roots should lie flat when viewed from the bottom.
  3. Cut out the taproot and create a space immediately underneath the trunk.
  4. Rinse in clean water; do not allow the roots to dry out whatsoever!
  5. Prepare a clean suitable pot.
  6. Cover the drainage holes with gauze and should the tree need to be secured with wire, now is the time to insert wire strips through the holes in preparation thereof.
  7. Fill the pot with a suitable soil mixture so that it forms a slight mound where the tree is to be positioned.
  8. Position the tree and continue filling with soil. Use a chopstick or any suitable stick to spread the soil through the roots being very gentle and careful not to damage them. Fill the pot allowing some space around the rim for watering.
  9. A fine layer of soil can then be added on which some dry moss can be sprinkled.
  10. Soak the tree in a bath of water until all air bubbles are expelled. Drain and place in a shady spot for at least a week.
  11. Do not fertilize for at least six weeks.

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Haiku

Grey marsh, black cloud...

Flapping away in autumn rain

Last old slow heron. ~ Anon

Random Bonsai Tip

Sacrifice branches can be used to thicken up the branches or the trunk by taking advantage of the auxins in the terminal bud. A low branch could thus be used to thicken the base of the trunk and so improve the taper.