May has been quite cold this year, but at least we haven’t had too many windy days. Hopefully, you have enjoyed some autumn colour from the deciduous trees in your collections, especially as we have had a bit of a break from the rain.

The sun moves lower in the sky during the colder months, so you may need to move your trees around to get more direct light. 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 are able to 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, 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.

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. You should also clean out any dead brown needles on black and red pines to 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 completely, 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. A lot of the trees in my collection are growing under cover so some insect pests can remain active there over winter if I’m not watchful. I also 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 toolbox 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 repotting. Personally, I feel a bit nervous about repotting my trees early in case they experience any die back afterwards. Once the sap is starting to rise (later in winter) and the leaf buds are beginning to swell, it’s very easy to spot the points to which you’d like to prune each branch. The first trees to break their dormancy will be such things as ornamental flowering quince and Virginia creeper, so repot these species first. In my collection, the pin oak has the longest dormancy, regularly not coming into leaf until October. Thus, if I need to re pot that tree in a season, I leave it until last.

If you have any camellias in your collection, these can be repotted immediately after flowering, before the new growth has commenced. You may be interested in buying flowering trees such as azaleas, camellias, ornamental quince, bougainvillea and Serissa, so 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. Although leaf size can be reduced over time with careful pruning of most species, flower and fruit size cannot be altered.