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Autumn and Winter Tasks

by Gail Theron

Bonsai growers tend to think that as their trees slow down towards the end of summer they can take a well earned rest, however, there is still much to do and think about.

  •  Watering

Do not skimp on watering Elms and Celtis just because leaves look tatty because this might result in tip die-back in winter. Maples can have their supply decreased slightly to encourage autumn colour, but be prudent about this. Bear in mind that as daylight hour shorten and temperatures decrease most trees need less water and adapt your watering program accordingly.

  • Position of trees

The sun intensity and its position can change quite dramatically so, do check on the light requirements for each tree and do not forget the regular rotation of the trees. Also make provisions for the change in the wind direction during autumn.

  • Pests

Keep a wary eye out for scale, woolly aphids, mealy bug, mites, caterpillars, snails, and thrips which can really cause serious damage to your bonsai if left unchecked. Make sure you use the correct and relevant insecticide at the correct dosage. There are many products on the market but be sure to consult an experienced grower - A stitch in time saves nine!

  • Fungal infection

Black spot can be a problem on Ficus use Benlate. Root - and wood rot fungi on Olives should be treated with Ridomil and Alliette.

  • Feeding

Many people totally neglect feeding deciduous trees after January, working on the theory that the tree will soon lose its leaves and, therefore, do not need food to sustain them through the winter. They then expect them to produce healthy, strong spring growth. A fertiliser low in nitrogen, high in potassium and phosphorus is recommended.

For deciduous trees, feed 2:3:4 monthly from January to March. Indigenous ever-greens have a strong period of growth in autumn. For Olives, Diospyros, Coleo-nema, and Ficus feed Nitrosol, on a monthly basis, through autumn and winter.

Exotic evergreens are fed once or twice during the same period. Flowering and fruiting trees need 3:1:5 in autumn.

  • Autumn repotting

The only species I am happy to bare root at this time of the year is Ficus. For other evergreens a repotting with only slight root disturbance is recommended.

  • Other chores

  1. CHECK THE DRAINAGE IN ALL POTS.
  2. APPLY LIME-SULPHUR TO JINS, SHARI, AND OTHER DEADWOOD AREAS.
  3. TREAT TIMBER STRUCTURES IN YOUR BONSAI-EN WITH WOOD PRESERVATIVE.
  4. COLLECT THE INGREDIENTS FOR SOIL MIXES.
  5. CHECK WIRED TREES FOR WIRE BITE.
  6. SHARPEN AND CLEAN TOOLS. vii. WINTER PRUNING.

Winter pruning takes place at a time of the year when, apart from maintenance chores, bonsai action is slow, it is an ideal time to assess one's trees. Not only in terms of design but also in terms of growth during the preceding summer. The type of growth gives one a clear indication of the correctness of one's positioning, feeding, pest control, soil composition, and watering. Die-back of major branches could be caused by:

  1. the tree not being turned regularly and a branch withers away from the lack of light.
  2. injury to the branch.
  3. careless wiring.
  4. pests, for example, scale, snout beetle and so.
  5. fungal infection.
  6. not sealing major scars.
  7. a lack of nutrients.
  8. apical dominance, depriving the lower parts of the tree of nutrients and light.

Tip die-back could also be caused by the above factors but the most probable cause is inadequate feeding or watering. The tree is unable to sustain itself jettisons branches as an act of self¬preservation. Autumn feeding with low nitrogen fertiliser such as 2:3:4 once a month from January to March should be practiced.

All deciduous bonsai benefit from winter pruning. It is a very important part of refinement. I tackle this task as soon as the tree has dropped its leaves. A really sharp trimming scissors is essential.

Remove all deadwood and stubs, then the design of the tree should be assessed and altered, if necessary. At this time of the year this is, largely, a refining exercise and the changes should not be major. The next step to trim every branchlet back to second or third eyes (remember to prune to an eye going in the direction you want future growth to occur). For trees with opposite leaves, for example maples, trim the branchlets and rub off the unwanted opposite bud.

Remove all branch trimmings and weeds from the pot because these harbour pests and fungus spores over winter. I have not used lime-sulphur in the nursery because it discolours pots, benches, moss, and so on. Where a tree has been plagued with pests and fungi during summer I use Folithion or Benlate (fungicide) on bare trees.

Winter is a very good time for photographing deciduous tree. Somehow the flaws in a tree show up better in photographs. It is very interesting to be able to follow a tree's progress through photographs.

 

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Random Bonsai Tip

Mixing growing medium - To mix your growing medium, put the mixture into an empty compost bag (as much as you can handle) and tip the bag backwards and forwards - this is much easier and more effective than mixing in a wheelbarrow!