Late February has been a lovely time for working on our bonsai, with a return to warm and pleasant sunshine and occasional rain.
The days are still warm, so keep up with the watering and feeding, taking particular care if it’s windy, as this can dry out the potting media very quickly. Keep an eye out for insect pests, as they are likely to be still active. I have had plenty of issues with sucking pests in my own collection already this year. Some may even be curled up in leaves. Wear gloves for this exercise, as you never know what you may find!
Use a low nitrogen organic fertiliser during autumn to harden late growth and improve flower and fruit production in spring, as 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 the summer heat, but the trees are now building up energy for the winter months, so need as much light as possible on them during the autumn. Shorter days and cooler nights are the plants’ message to slow down, so move trees like liquidambar, ginkgo, Chinese pistachio, Manchurian pear, maples and zelkova into sunnier spots, which will also help improve their autumn colour. Autumn is also a good time to buy these plants when they are in colour so you know what to expect in future years.
Remove any dead leaves and check that the surface of the soil is free of dead foliage, as this may harbour fungal disease. 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.
Autumn is not the time to 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.
Prune pines, if you haven’t already done so, by removing candles once they are one to two centimetres long. Leave strong candles to develop on weak branches and weak candles to develop on strong branches. Remove any brown needles and check branch structure, as in some areas multiple small branches may have developed over the growing season. Keep the branches that are growing in the right direction for your design and remove any that are too cluttered or are growing from the same spot as one you want to keep.
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.