Hopefully all your bonsai trees are now being protected for the winter and here is a quick generic guide to bonsai in November as the colder weather has now arrived in the UK.
Preparation for Winter
Check all your bonsai trees for health to ensure that before they are all in good health before the change in weather as the stronger your trees are the better chances they have of coming through the winter in good health.
Ensure that before placing them under cover or into a cold greenhouse that the leaves for broadleaves have been removed as dead leaves rot and can cause mold and fungi to build up and affect the buds for next spring.
Your bonsai trees will still need watering but not as often as their growth rate has slowed right down so the water uptake has also slowed down and the trees are going into winter dormancy.
At this time of year if your trees are still outside, they will be getting watered naturally by the rainfall, morning dew and melting frosts. However, monitor the moisture level to ensure your bonsai trees are not water logged as this can cause roots to rot.
If your bonsai trees are under cover check daily and water if required to keep the soil damp / moist but not soaking wet.
Any bonsai being kept indoors should be watered regularly but this will have slowed down from a daily watering. They will be loosing moisture due to the higher temperatures inside drying out the soil and the tropical species still tend to grow during the winter period inside.
Ideal time to water is in the morning to allow the water time to dissipate and to reduce the surface water should the temperature cool down overnight or there is a frost.
This is a great time of year to review your bonsai trees and check the structural image of the tree as well as the tracery and branch placement. Broadleaved trees are especially easy as they have for most species lost their leaves and are dormant. You can remove unwanted structural branches but remember to cover the wounds with wound paste or sealant as the trees are dormant and will not be able to respond to the pruning as effectively. Otherwise just mark the branch(es) to remove and wait till the Spring to then remove them.
This is not required to either broadleaved or coniferous trees in November. However, you may still need to trim the new shoots off tropical trees that are growing indoors to control the growth and develop ramification.
Insects and pests
Continue to check your bonsai trees over fully for pests, insects and diseases as some insects can over winter on or in your trees like red spider mite, scale insect and if you have not applied a winter pesticide or removed unwanted pests before now it is a chance to do so.
Pests are also likely if the weather is mild so worth checking to avoid disappointment in the spring when buds or leaves fail to flush due to pest attack. Typical pests still around include scale insect, mites, aphids and soil borne larva, vine weevil and beetles.
Moss and weed control
This is the time to carry out pre winter preparation and to remove any weed and moss issues particularly around the trunks of bonsai trees prior to winter.
The aim is to have a clear surface of the soil for improved moisture movement as well as prevent bark rot from wet moss. You can use a range of techniques including a diluted vinegar application on the bark which you apply and then around a week of two later the moss removes more easily with a light brush action (tooth brush works well).
If wire is present on your bonsai tree check whether it is still serving a purpose and is taught and not digging into the bark causing wire marks and re-set if necessary or tighten.
This is also a good time to wire Pines and Larches to set the branches over the winter and it is an easier time to wire certain species like broadleaved varieties as the leaves have fallen off.
For those trees in your bonsai collection that are more sensitive to cold weather try to provide them with some winter protection from the frosts especially if they are in small pots. The smaller the tree the more vulnerable to winter weather damage they are.
Options for protection include
- Under benches
- Cold greenhouse
- Cold frames
- Shade netting
- Double potting placing on pot inside a larger pot
- Pot protection with fleeces, polystyrene, wooden box
Certain tree species are more vulnerable due to their sensitive foliage type or root type so protect species like Yews, Ginkgo’s, Ilex, Swamp Cypress and species with fleshy roots. Continue to maintain winter protection in whatever form you use and check your trees daily for effects of frost or snow.
If the weather is mild repotting can be undertaken but avoid early repotting if you have no protection for the tree like a cold frame or green house if frosts are likely. However given that the frosts have started here in the UK avoid repotting now until the spring. Prepare instead for repotting by checking soil supplies and also that if you are looking to change the pot that you have the correct pot size to repot into.
Generally feeding in November is not required as broadleaves trees are dormant and without leaves and conifers or evergreens have slowed down on growth during this period. However, continue to lightly feed tropical trees that are kept indoors if they are still showing signs of growth to sustain them during this period.
This is also a good time to photograph your bonsai trees and update their records for re-potting timings, feeding regimes, soil type etc as it is sometimes hard to keep track of what you do for each tree when you start increasing your collection. Keeping a photographic record does come in very useful over the years to see the trees development and your progress.