5 Things you should be doing with your bonsai in Autumn

With every passing season we need to be aware of what tasks are required on or around our trees. It is possible that depending on your location some of these tasks might differ, but many of them will remain the same. There is no substitute for experience of course and it is always such a big help to belong to a local bonsai club where you can chat with and learn from other bonsai artists, or of course share your knowledge also.

Image caption. Kyoto in Autumn, with maples in all their glory

I've identified a few tasks which I do my level best to get around to at this time of the year, which where I live is the Western Cape of South Africa is Autumn. In this first part of a two part series I will share some tips which you should do, in the second part some tips of what you should avoid doing. 

These are not rules, merely suggestions which you might need to adapt to your location.

Tip #1 Do make sure your trees are getting enough sun.

Image caption. A Japanese red pine cascade in Omiya Bonsai Village, Japan in full sun maximising the energy it gives.

In summer the sun is pretty much overhead, but it will move lower over the horizon now. Depending on where you have your trees in your garden this may affect them. Be aware of the specific needs of each of the species you keep. For instance if you keep evergreens such as junipers and pines, these need as much sun as possible, so you may need to move them to a sunnier spot.

If you keep many deciduous trees, they will be losing their leaves now and not really requiring much sun anyways so with them I am not too worried other than the fact that I don't want them in full shade or the containers will never dry out.

Tip #2 Do make sure you adjust your watering.

Image caption. Always water with as fine a nozzle as possible to avoid eroding the growing medium in your containers.

I've always felt that this time of the year and even winter, when there are periods of no rain, watering is really tricky.

It's cold outside and perhaps it rained the previous day, so you think it is not necessary to water. Be careful of making this assumption! If you have some trees with fuller foliage canopies it is often the case that the foliage will prevent rain from getting to the container below, and you may find that these trees are bone dry when you eventually notice this.

On the other hand one should be cautious of assuming that if it rains that you need not water at all. The containers our trees are in are very small, and unless its pretty much a downpour it could be that insufficient rain will reach your container.

Always try to water your bonsai with a fine spray. Its also useful to use a watering can with a fine spray, for spot watering those trees which need a little water when the rest of your collection does not.

Tip #3 Do fertilize generously.

Image caption. "BonsaiBoost" on a Japanese maple at AichiEn, Japan.

Out of all the times of the year, this is possibly the most important time to be fertilizing your trees. The reason is that the nutrients which you provide to the tree now will ensure that it is nice and strong for the spring which is to come.

This tip applies to all trees I can think of, whether it be a Chinese maple or a White Pine. In fact if you have mature specimens of these two species which I have just mentioned, it is best to feed them now as a lot of fertilizer in spring will only give more boost to the spring growth, leading to ugly and unwanted long internodal growth.

I always recommend organic fertilizer, of which there are many on the market today. The main ones of course being solid and liquid:

• Solids can be placed into fertilizer baskets, so they don't get washed away, flies don't lay their eggs in it and it does not damage the moss as much. I use almost exclusively BonsaiBoost on all my trees as it is convenient, easy to use and lasts for about 1 month.
• Liquids need to be diluted according to the instructions and applied regularly as the nutrients are quickly washed from the bonsai container, due to your frequent watering.

Tip #4 Watch the drainage of your containers.

Image caption. When you water, make sure the water runs freely from the pot, if not you may need to consider repotting in spring, or in severe cases an emergency repot might be needed. Check that no slugs have made the recess of the drainage hole their home, as this could also lead to impeded drainage.

I'm not a botanist but I believe that it is not so much the excess of water which can debilitate a tree or even kill it, it is the lack of oxygen in the root zone which causes the tree to drown. 

This might sound like semantics and it may be confusing. What I mean is that if your pot or more specifically the growing medium your tree is in, does not drain well or if your drainage holes or drainage mesh are blocked by some obstruction (including slugs!) then water will fill the container and could eventually drown your tree. However if your growing medium drains well but retains water this means that the particles retain water and although there will also be moisture between the particles, there will also be oxygen. So your tree will be ok. Read more about repotting and growing mediums in general in this previous blog post.

As we move into a period when we can expect more rainfall you need to observe how quickly your pots are draining. If it looks like the water is pooling and taking forever to drain you may consider doing an emergency repot into something like our Professional Mix or even better, Pumice. Disturb the roots as little as possible but try to shake off all the old growing medium and then without cutting any roots just place the whole tree into this free draining mix. You can use the same container or a larger one, or you can use one of our clay development containers as these will further promote oxygen and water exchange (of which we stock several different sizes and with plenty of drainage holes.)

Tip #5 Do your final pruning and wiring of the growing season now.

Image caption. Defoliate, prune and wire your trees when the leaves begin changing colour, not in dormancy of winter when no sap is flowing.

As a general guide, when the leaves of my deciduous trees change colour I cut them off and I do the final pruning of the season. A pair of trimming scissors is ideal for the task as it allows you to get right into the branching of the canopy. Be sure to seal all cuts with a good sealer to assist the healing process and also to prevent sap loss in spring.

The leaves are not serving any purpose as they are dying, hence the colour, and removing them now and then styling the tree allows you to still catch the tree with a little sap flowing and begin to heal, but you are also not in danger of damaging any tender spring buds when you apply wire now in order to set the branches which grew this past season in place.

When you prune keep in mind the outline of the tree and prune to this. Bear in mind the direction of the dormant buds you are pruning back to and where you want to direct the spring growth to. This advice applies only to more developed trees. With developing trees where sacrifice branches are still in use, don't prune them back at all, although you may wish to eliminate any side growth from these branches. If the sacrifice branch has served it's purpose then it can be shortened or eliminated altogether, although if a large cut is to be made it is better to wait till late spring to do this. Use an appropriately sized branch cutter for the purpose and seal.

Should you decide to wire now you need to be especially careful of young trees as they are full of energy so in spring you may need to remove the wire early because leaving it on may lead to wire bite. Its best to use soft wire such as anodized aluminium wire as it's easy to apply and gentler on the soft bark which most deciduous trees have.

I don't work on my deciduous trees during winter. This is as any wire applied then may lead to branch dieback, because essentially when you wire you are making fine breaks in these branches and now that there is no sap flow they cannot heal. I also don't prune my deciduous trees in winter as they are unable to heal, also as there is no sap flow. So in spring, trees which have powerful sap flows will bleed a lot, which is simply a waste of growth.