Amazing to have experienced two such totally contrasting summers! This one just finished was so wet and cool, and the one before so hot and dry. I hope that you and your trees have survived both well. The main thing I seem to be doing after the recent rain is weeding! Some of my trees have a veritable ground cover of seedling weeds which need attention.
The days are still warm, so keep up with the watering and feeding, taking particular care if it’s windy. Keep an eye out, as always, for insect pests. Some may even be curled up in leaves, so hunt carefully. I just trimmed back my jade plants. I have a few as bonsai, a couple of cascades and a raft style that I purchased from another member several years ago. I was delighted to discover a tiny praying mantis on one of them when I was pruning. I am reminded to only use insecticides when absolutely necessary, as such beneficial creatures are searching for the insect pests I hate for their dinner!
Use a low nitrogen organic fertiliser during autumn to harden late growth and improve flower and fruit production in spring, because plants need to store energy as we approach winter. Remember to use a fertiliser low in phosphorus for your natives.
The foliage on your deciduous bonsai may have suffered during summer, but the trees are now trying to build up energy for the winter months, so try to get as much light as possible on them during the autumn months. Remove any dead leaves and check that the surface of the soil is free of dead foliage, as this may harbour fungal disease. If the weather is not too hot, move trees like liquidambar, gingko, Chinese pistachio, Manchurian pear, some maples and zelkova into sunnier spots to improve their autumn colour. Shorter and cooler nights are the plants’ message to slow down, so as much sunshine as possible helps their colour. Autumn is also a good time to buy these plants when they are in colour so you know what to expect.
Tidy up figs by removing any overly large leaves, and cutting back any shoots that are too strong for the rest of the tree. Elms and other trees, particularly evergreens, that have thrown out long branches can be cut back to help develop ramification. Reduce the density of foliage as well, by selectively trimming off unwanted shoots and leaves. Check your trees for wire that may be cutting in, as branch girth may have increased recently. If branches have not yet set to where you want them, rewire if necessary. If there has been any cutting in, it’s a good idea to re wire in the opposite direction to the last time.
Don’t cut back deciduous flowering trees or plants such as azaleas and camellias, as you don’t want to remove the flower buds that are hopefully forming for next season.
Autumn is also a good time to start preparing your potting mix, as there will be plenty of use for it later in the season and during the winter months.