|Hopefully with all this rain this year you have checked your bonsai to be sure they drain properly. Very few plants will take any length of time in a pot full of water.
Even so you must get your trees prepared to take on the Texas summer. Remember that the biggest stress on potted plants comes from the soil being heated, especially by the late afternoon sun slanting in under the shade cloth and foliage. The low humidity in the afternoon does little to stop the heat. You need to provide good shade on the west side. Two waterings are sometimes needed--one about 2pm to cool the soil and provide for evaporative cooling and another later about sundown to get the soil temp back down and to allow the plant to be able to rest at night.
Leaf pruning should not be considered a yearly task. It usually should be done only as needed and only on very healthy trees. Broadleaf evergreens would not get it. I usually consider Memorial Day as the end of leaf pruning.
If you think you need to leaf prune, you probably can still do it but need to be careful, it could turn hot in a hurry. The tree needs time to replace the energy used to grow new foliage. I have done it on Shumard oaks successfully. Again never leaf prune the atropurpeum varieties of Japanese maples, they dont rebud very well.
When night temperatures stay above 60 degrees you can think about repotting some of the tropicals. I would wait another month though for the buttonwood.
However, some tropicals can be leaf pruned all summer. The Ficus nerifolia especially benefits by leaf pruning and can be done more than once each summer. That will develop the heavy twiginess you see in the Ficus bonsai from the Far East.
As the summer progresses the growth of the deciduous trees will sometimes slow also. But you still need to keep an eye out for errant shoots. Keeping a clipper with you when watering would let you take care of most of them. Just like in the spring a shoot too long will thicken the twig too much. The major pruning chore is now transferred to the tropicals.
Tip pinching on some flowering species like the crape myrtle will result in fewer flowers but if you let it go they get out of shape. I prefer to try to balance the flower/design question by pinching early. This provides more growing tips to divide the energy and the resulting flower is shorter. It is less showy but more in scale.
Also, if you have fruiting bonsai, you should reduce the number of fruit on the tree. The number one goal of the tree is to provide seeds for reproduction and it will starve itself in order to do so. Again, most fruit are too large to look good on a bonsai.
Some days may be relatively cool to you but the sun can still make the pot pretty hot. Not only does this dry out the soil very fast but the tree roots do not like a hot soil. A temperature I have heard given is that 120 degrees will kill roots on most plants. I cannot give you a precise to-do list since your backyard is different from mine but you should be sure that the sun does not hit the pots directly. Notice especially where the hot afternoon sun, from 2pm to sundown, hits your bonsai area. If you use a cover of any kind be sure that the side of the pot is protected also. A loose weave cover is preferable to solid paper or foil. Chopped sphagnum moss spread on the soil surface will reduce evaporation and help keep the soil cooler.
Get to know your trees like your children. Which ones use more water and which ones stay moist between waterings. If some are difficult to keep happy you can try moving those to a cooler location (but be sure they get their sunlight). Another trick is to group these together so that you can hit them with a shot of water twice a day and not have to spend the time going through all your trees.
The extended cool and damp weather is good for fungal diseases like black leaf spot. Hot and damp bring other fungals like mildew. Treat with potassium bicarbonate or sodium bicarbonate (baking soda). After the foliage is hardened a bit you can treat with a 1% hydrogen peroxide (1 part 3% peroxide to 2 parts water) weekly.
Also watch for signs of insect problems. The spider mite will always be near. Others to look for are scale of various forms, aphids, and mealy bugs. For scale you may need to go to a systemic insecticide. I use the organic foliar feed (1 Tablespoon each fish emulsion, liquid kelp, molasses and cider vinegar per gallon water) to control all these. You can use some of the other organic controls or a chemical according to label directions. Always read the label directions carefully and never apply oil based chemicals to buttonwoods. You should do controls on a regular basis. Also remember that most insecticides kill the insect but do not remove the evidence (the scale shells, webs, etc),
If ants, or any other creature, are building nests in the soil, the tunnels and cavities will prevent proper watering and result in a loss of roots. After you get rid of the ants be sure to grab your chopsticks and work the soil down and eliminate any holes. You will probably need to add a little more soil on top.
The best way to fertilize bonsai is by using fertilizer cakes. The cakes provide a slow constant feeding each time you water. Cakes made with a cottonseed base will provide as acid ph when they break down which we need in any city water system I know of. Making your own is easy and much cheaper than buying them. I use chemical fertilizers such as Miracid or Peters a couple of times a month also. My main problem with chemicals is not knowing how many bad salts they have that may accumulate in the soil and also I know that each time I water I am washing the chemical fertilizers out on the ground.
By John Miller - Reprinted From 2015|