Updated 2018/08/01
Its winter, its freezing cold, wet and windy in Cape Town.
Smooth bark Elms are already green and cork bark elms’ buds are also starting to swell. This is the busiest time of the bonsai calendar. Its time for designing, pruning and potting of most your bonsai.
Start potting your deciduous trees, i. e. Celtis, Elms, Maples, White Stinkwood, Birch, but it’s already becoming late for swamp cypress. Finish potting your swamps before the second week of August. Swamp tend to “bleed” a lot if cut too late in winter. Acacia can be potted from the middle of August. Leave Figs for later in the year.
First plan what you want to do with your tree. If you want to repot it to a new pot then make sure you got the right pot available before potting. Keep a suitable container with water in it ready to dunk the tree after you repotted it, if you use the normal bonsai soil mixtures. If you make use of Akadama, pumice or Leca in your soil mix then don’t dunk your tree. These three (Akadama, Pumice and Leca) will float on top of the water if you dunk it.
Finish wiring, pruning and designing your trees before potting it. Do not do “dramatic” styling work on junipers and pines if you plan to repot them. “Dramatic styling” will place junipers and pines under stress and if you repot it at the same time it can kill the tree. Rather do the ‘dramatic styling’ one year and repotting the next.
It’s important to make use of wire on your tree to achieve the best results. Rather spend several hours wiring your tree to get the best result, than saving some time and wire and neglecting the design and progress of the tree. It may sound strange to most to say that it will take hours to wire a tree, but basic medium size maples can take up to four hours to wire properly, wiring every little branch designing the tree. It will be beneficial for the development of your tree to wire the whole tree every 5 to 7 years. In Japan they can take several days to prune and wire a single mature tree.
Beware that Maple branches are very brittle this time of the year and will easily break without warning. A better time to wire maples will be late spring or summer. When defoliating a maple its normally the best time to also wire them. The branches are then more flexible.
Do not feed newly potted trees. During potting you remove a lot of the roots and the tree cannot absorb the chemicals. The chemicals can also burn and kill the new roots.
Remember aftercare is the most important part of repotting. You can do the best job in repotting the tree but only one warm day in which your tree is not protected from the heat or wind will kill your tree. A good after care spot will be a cool, protected (wind and sun) area, where the tree will get enough water. The soil must not be too wet, neither must it dry out. I prefer to give a light spray on the foliage of newly repotted trees several times a day for the first three weeks, only watering the soil when necessary, trying to keep a moist environment around the trees. Also make sure that your tree is stable in its pot. If the tree appears to be a bit loose in the pot, while you are potting it, tie it down with wire through the drainage holes of the pot. (especially if you make use of Akadama, pumice and Leca in your mix) Just remember that you wired the tree. You will need to remove it later when the tree formed enough roots to support itself. Leaving the wire on for too long can damage the roots, even kill them. Trees like Acacia take a long time (up to three months) to form new roots, and in places like Cape Town with its wind you need to keep them tied down or in a protected area for long enough to form enough roots, or you will find a lot of slanting trunks in your collection.
We get a lot of rain so make sure that your trees are draining properly. Go out during the rain and see that the water is draining out of your pots. If the water stays in the pot the roots will start to rot and your tree will die during the winter without you noticing it.
If the pot don’t drain well place a wedge under the one side of the pot so that the tree stands skew and the water can run out of it. Also check that your pot’s drainage holes are not blocked. Remember to repot those trees that do not drain well and replace the soil with a better draining medium.
Also be aware that even though it rain, trees that’s placed under shade cloth or in protected areas can dry out if the rain do not reach their pots.
Look out for moss development on the bark of the trees. It can cause the bark to rot away. You can control the moss by spaying vinegar on it in the areas where you want to kill it.
Treat deadwood with pure lime sulfur to prevent it from rotting in the cold and wet winter months. Wait for a warm dry day to treat the deadwood.
You can still collect trees like wild olives. Wild Olives that were collected during May are already showing signs of new little buds.
Bonsai like Azaleas, Flowering Quince and Coleonema Alba started to flower. Remember to remove spent flowers. Azaleas can be potted as soon as it’s finished flowering.
If you wire your trees in winter beware that the branches can be very brittle and can easily snap if you bend them too far. Rather bend the branch over a period of time.
In the past few years many different diseases appeared in bonsai collections. We mostly speculate on the types of diseases as well as the desired prevention and cure with different information being obtained from many different international sources.
The best preventative measure for most diseases is a healthy bonsai. Root rot can be prevented with well drained soil and the correct watering methods. Fungal diseases again thrive in warm humid conditions. A healthy bonsai got the energy and natural resistance to fight these diseases.
Some of these diseases that we found recently are anthracnose, a fungal infection found on several trees but mostly Japanese and Chinese maples. You can recognize the infection from the newly formed leaves will shrivel up and turn black as soon as they start to open. It look can look similar to wind damage to young leaves. So far the best remedy appears to be a fungicide “mancozeb”. It can be sprayed as a preventative spray on maples. Spray it on the tree as soon as the buds start to swell, a second spray when the buds start to open and again 10 days later. Make use of the indicated dosage on the label. Several products has mancozeb as active ingredient. One of the readily available products is ‘Unizeb 800 WP’. Use as indicated together with “SK eco oil” as wetting agent and additional fungicide.
Wooly aphids, thrips and scale can be prevented with Koinor.
All these products available from Terry.
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