A quiet time for bonsai. Keep watering, very little but adequate. Ensure that any watering is done in the morning so that there is sufficient time for the surplus to disperse before freezing sets in. If the winter is severe and the soil remains frozen day and night, do not allow the trees to suffer these conditions for many days, but transfer to a cold bedroom, shed or garage to enable the soil to thaw and the roots to take up moisture. Do this as often as necessary.
Now is an excellent time to study every tree with an eye to the eventual shape.
Take photographs to help with the planning, thus maintaining a complete record of the progress of each individual tree in your collection.
A time for planning and preparing for the busy time ahead in the spring. Make notes of which pots you will be using for the various trees you will be repotting. Some will need large pots, some deep, some with different shapes etc, all of which you could have made mental notes of in the preceding summer months when in full leaf.
It is an ideal time to collect loam, pine needle mould, sand or grit and peat and prepare for repotting.
A general guide to the mix is 30% loam, 30% sharp sand or grit and 40% pine needle mould or coarse Irish moss peat. Having sieved the constituents, mix together with a small amount of bone meal fertilizer. This gives a good open mix, so essential for the health of bonsai.
Should there be any trace element deficiency this can easily be overcome with regular feeding If you cannot collect your loam, John Innes No. 2 can be used, but first sieve out the small dust. Pines may now be given a little feed.
Potting and repotting can now commence as the buds begin to swell, provided you can protect from high winds and late frosts. Young trees will need repotting more often than older ones. Lift trees from pots and trim roots as necessary. As you repot, raise the tree about a quarter of an inch higher than the previous year, and gently scrape away the soil from around the trunk. This way you will gradually expose the root and make a more interesting bonsai.
Older trees that you have decided not to repot can benefit by carefully removing the top half inch of soul, avoid damaging the surface roots and replace it with new soil mix. This practice will remove the weed seeds that may have settled and any pests that have over wintered and generally give your bonsai a fresh look to start this season.
Clean and sterilise your display area.
A good time to collect any trees from the wild that you may have had your eye on, but remember to obtain the owner's permission first. Take your time and lift gently from the soil retaining as much hair root as possible. Cut the tap root and seal with Arbrex. Place the tree in a deep pot or box with a good open mix and pray! If you can get some Superthrive, this will increase your chances of success.
Some deciduous trees will start to show their leaves now, so bring them out of their winter quarters but keep a watchful eye for frosts and strong winds, leaves are very tender at this stage. An exciting time this, when you see the signs of life, hopefully, on recently collected trees. Also to see if the winter has caused any damage among your collection.
A month of fast and exciting growth for most trees. Begin your feeding programme with a liquid manure, once a week as a guide. Ensure that the manufacturers' instructions are adhered to. Remember it is safer to feed a weak solution more frequently than a strong dosage irregularly. Older, more mature trees will not need feeding quite so often.
Shape your trees by pinching the new growth and training where necessary, do not wire until the new growth has hardened. Keep the top growth well pinched so the lower branches are not starved, thus ensuring they are kept strong and healthy. Also make sure upper branches do not over develop creating shade to lower branches, this may cause problems later.
Pinching growth early will ensure short internodes and encourage fine twigs structure so necessary for good bonsai. Spray for any bugs or mildew as necessary, but avoid doing this in strong sunlight. Use a weaker solution than recommended as the leaves are very tender at this stage.
Protect from strong winds and late frosts. The demand for water will increase considerably, so watch your watering carefully. To encourage silver birch to obtain the silvery effect keep nitrogen feed low.
Leaf pruning of deciduous trees can be done in early June, but only if they are healthy and vigorous. Cut all leaves, leaving as much of the leaf stalk as possible. In about three weeks fresh leaves will appear, being slightly smaller and more to scale. DO NOT leaf prune a sick tree and if you are not certain then just remove the large objectionable ones.
All trees will benefit from spraying with water in the evening, when the sun has gone off them. Spray under as well as on top of the leaves which will also discourage red spider. The trees should get all the sun they can tolerate without getting leaf scorch, and should be turned occasionally to ensure even growth.
Watering morning and evening will be essential now, so do not neglect it. Keep shaping your bonsai by snipping and wiring to your design.
Air layerings will do well at this time. This must be the best time of the year for seeing your bonsai at their healthiest, with beautiful new growth and lovely green colours, so enjoy them.
Reduce the nitrogen in your feeding for trees like maples and zelkovas if you want the best autumn colouring.
Do not leaf prune now except for badly scorched leaves, as once they are brown they are not working anyway. Constant watering will encourage moss, whilst this will enhance the presentation of the bonsai, do not allow to completely cover the pot. Liverwort will also take a hold, this is always unsightly and will quickly spread, so weed out as quickly as possible.
At this time you will probably be spending a lot of time in the garden, with the trees in full leaf and at their best now is the opportunity to sit and study them from all angles. Plan their future shapes by sketches etc. Make notes, however trivial, as to the various happenings to your bonsai, so you can look back and compare. You will soon know their likes and dislikes and what position they do best in etc.
Photograph your trees to maintain a complete chart of progress. You will be surprised when you compare photos what a difference a year makes Watch for caterpillars as they can strip a tree quickly if undetected.
Continue your fertilising programme and watch the weather carefully. Do not fertilise when the soil is bone dry. Always give the soil a soaking first before applying fertiliser, otherwise it can burn the roots. Remember, heavy rain can wash fertilisers out of the soil. Pines will need far less fertiliser now than the deciduous varieties, fruiting trees require fertiliser high in phosphorous. Azaleas and pines would benefit from a feed of Sequestrine. Soil will soon dry out with strong sun, even more with strong warm winds, so watch the watering.
Continue to turn trees to obtain even growth. Keep spraying regularly for red spider mite and aphids etc. Inspect any leaves that may be stuck together as this invariably means young caterpillars and much damage can be done.
Watch your wiring as, with your bonsai now building wood being in full growth, the branches expand and could lead to the cutting wires leaving bad scars.
Willows do well with their pots set out in shallow dishes of water in really hot weather.
With the reduction of activity in your bonsai pinching out leaves is no longer necessary.
This month can be hot and dry so maintain watering. Any fertilising should now be done with a liquid feed as this is quickly absorbed compared with solid feeds which take two to three weeks to break down. Use fertilisers mainly of potash and phosphorus and very little nitrogen, which, along with carefully controlled watering will greatly enhance the autumn colours.
Quince, pomegranate and other early flowering bonsai will benefit from repotting in a larger pot. DO NOT root prune or disturb the roots, but add extra soil which will encourage good flowering in the spring. You can always revert to the smaller pot when root pruning after the flowering has finished.
Keep a watchful eye for insects looking for their winter quarters.
Trees, especially deciduous, wired in the spring should now be set and the wires can be removed.
Watering can now be cut back but still give the trees as much light as possible. Junipers and pines can be wired and pruned for shaping.
Get rid of the mosses for winter, they only hoard weed seeds and insects, especially leather-jackets.
Start thinking about your winter protection for most of your trees.
This month your bonsai can give you as much pleasure as in the spring with their leaf colourings before the trees go into dormancy.
Most of your bonsai will now be dormant so greatly reduce the water and in no circumstances use fertiliser other than bone meal.
Check all your deciduous trees carefully, should any dead leaves cling to the branches this invariably means pests have made their nests and they will spend the winter feeding on the bark. They may leave unsightly scars and in some cases lead to the loss of smaller branches. Larches are especially prone to this.
With branches bare, now is the time to spray with tar oil insecticide such as Nortegg. Remove any wires previously forgotten and clear moss to prevent harbouring pests.
Generally tidy up your bonsai. A good watering with a soil pesticide will take care of leather-jackets or pests that lurk in the soil, without harming the roots. Follow the manufacturers' directions closely.
Serious consideration should now be given to winter protection for your bonsai. A cold greenhouse or coldframe is ideal for any tree thought to be susceptible to frost damage; also one is able to control the watering by protecting them from heavy winter rains. Always give as much light as possible.
If you do not have many trees, a good plan is to display them on their benches during the day, putting them away at night, a bit tedious but well worth it. Deciduous trees can still be admired during the day for their excellent winter shapes.