Our autumn in Sydney had some fairly cold days, forecasting the fact that winter was coming, and is, in fact, now here. With the sun moving lower in the sky during the colder months, you may need to move your trees around to get more direct sun. Keep frost tender trees under protection if frosts are likely in your area. My trees do not have ideal growing conditions, living as they do mainly on the western side of our house. However, during winter I’m always thankful for the extra sunshine they receive at this time. For me, summer is much more problematic light-wise. It’s important to know the light requirements of the species of bonsai that you are growing, and make appropriate adjustments based on your own growing environment.
To prevent your bonsai trees from having constantly cold, wet feet and damp foliage, it’s important to reduce watering for winter. Soil still needs to be kept moist so try to only water in the morning, which gives time during the day for some drying out to take place. Unless the weather is very windy, the frequency of watering can be reduced during winter to every second or third day. In my collection the crepe myrtles and crabapples are my ‘sentinel’ trees, which wilt first to show me I need to water during summer. In winter this is more difficult to monitor, as dormant trees won’t give any such signals, and conifers won’t show the sad results of having been allowed to dry out until several weeks later.
Remove spent flowers and fallen leaves and keep soil surfaces and benches clean to allow adequate air movement and the sun to penetrate properly through the branches. This practice will also prevent the harbouring of pests and diseases in your collection. Clean out any dead brown needles on black and red pines to also allow the sun to filter through to all the branches and make the trees look tidier. This applies to other conifers, for example junipers, as well. You can use tweezers for any hard to reach spots.
There are a lot of insect pests that are usually dormant or die out over the colder winter months, particularly in frosty areas. Insect life cycles are usually very short, and from April through to early September there is a break in most of their attacks on our trees. This includes Azalea lace bug, which is only around during the warmer months, although the mottling they leave behind on the leaves of affected plants might suggest otherwise. I have found that scale and their pesky relatives, such as mealy bug, can survive well over winter, though, particularly in sheltered areas, so it’s handy to have something like David Greys Systemic Bug Killer granules on hand. These are sprinkled onto the soil surface then watered in. I have beehives in my garden, so need to be cautious about what I use on my trees, particularly flowering species. I only use any pesticides if absolutely necessary.
Because of all the rain we have had this year, moss may have grown over the roots and onto the trunks of some of your trees. This can be removed by gently brushing with an old toothbrush, taking care not to damage or lift the bark underneath. Your trees will look much tidier afterwards.
Clean out your tool box and check for all the equipment – tools, wire, turntable etc. in readiness for the deciduous repotting time which is creeping up on us. Your tools may also need some attention such as cleaning, oiling and sharpening, although they are best maintained regularly whenever they are used.
It’s a good time to start preparing your potting mixes as well, as you are bound to be requiring plenty as winter progresses. Once a deciduous tree is dormant it can be repotted, but unless your collection is very large and thus due to time constraints, it’s best to wait until July or even early August to start