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. As the days become shorter, it can be difficult to get enough hours of sunlight each day. Keep frost tender trees such as tropical figs and bougainvillea under protection if you get frosts in your area, but still try to expose them to as much sunlight as possible.
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, but 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 when their foliage may start to brown off. Maples in particular may show signs of die back at the tips of branches (obvious at the start of spring when growth commences again) if they are allowed to dry out during dormancy. In your own collection you need to have a system of checking that ensures your trees are moist, but not constantly wet, over winter.
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 allow the sun to filter through to all the branches. Remove any brown or damaged foliage on other conifers, for example junipers, as well.
Natives and conifers should be grown in full sun over winter, as they will benefit from the light available. Any frosty nights won’t have a detrimental effect on them either. Many natives continue to grow actively throughout the winter months. Some are adapted to have a dormant period at the peak of summer instead, as a protective mechanism in the sometimes harsh Australian climate.
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. It’s a good time to start preparing your potting mixes as well. Once a deciduous tree is dormant it can be repotted, but unless your collection is very large and thus due to time constraints, it is best to wait until July or even early August to root prune and repot. The first trees to break their dormancy will be such things as ornamental flowering quince and Virginia creeper, so repot these species first.
If you are interested in growing flowering trees like azaleas, camellias, flowering quince, bougainvillea, serissa etc. keep a look out for them at nurseries and other plant sales. These are best purchased when in flower, if possible, so you know what to expect in terms of colour and flower size. Remember that the smaller the flowers are the more suitable the plant will be for use as a bonsai.