5 Things you should not do to your bonsai in Autumn

In the previous part of this 2 part blog post I wrote about some of the things you should be doing in Autumn. In this second part I will mention a few which come to mind as things you should not be doing.

#1 Do not repot any bonsai now

I am not sure why, but lately I have been receiving several emails and calls from people who want to know if I can repot their bonsai trees for them. Although this is a service which I offer, it is generally the wrong time of the year to be doing this.

The reason is simply horticultural. Trees are now changing to a state of dormancy, hence sap which was in the parts of the tree above ground are now moving into the parts below ground; the roots. It is also why feeding now is quite important, as I mentioned in the first part of this series. In spring this stored up energy will move up into the tree again and when you see buds swelling this means the sap has pushed up hard enough for the new growth to begin emerging. This is the perfect time to repot deciduous trees.

Were you to cut the roots now where will the tree store its energy? You may not kill the tree but it will be seriously weakened in spring and will take at least a season to recover. If you repot too early in spring the result will be less damaging but you will also limit the amount of sap which makes it to the branches and twigs and therefore the spring growth will be stunted.

Image caption. Hackberry or Celtis Sinensis is often one of the first trees to be repotted in spring as there buds begin swelling weeks before many other species. Notice the new green buds on the example, this is the best time to repot.

So do not repot now, wait until you see new spring movement on your trees and then repot. And please do not work to calendar months, watch the tree! The tree will tell you when it needs to be repotted, if you know what to look for. Read more about repotting here.

As with all "rules" there are always the exceptions. One of these which come to mind are junipers. When the seasons growth has hardened off (easiest way to check this is the colour of the foliage changes from a bright green to a deeper, bottle green) it is possible to repot. However you need to be aware that if you do a full repot then I'd advise against doing any dramatic foliage reduction over winter as this will seriously weaken the tree or even kill it.

I should add here that in the W.Cape there are several indigenous trees which we are learning about that might be able to handle repotting at this time. If you know from personal experience which species this applies to, please be so kind as to let me know so I can edit this post.

#2 Do not move your trees indoors

I cannot tell you how many people send me photos of dead or dying bonsai. After some investigation it emerges that the trees have been either kept indoors since they were purchased from the nursery or they are moved inside at night and outside during the day. I am not sure where the idea came in that bonsai are somehow unable to survive the outdoors but in fact to survive an indoors climate is far more challenging for a plant.

Although there are some more tropical trees which can be kept indoors, under the right conditions, all other trees should remain outdoors. Period! You can of course bring your tree or trees inside for special occasions and indeed when we exhibit trees they will often stay indoors for some days. That's ok, but you cannot keep your trees indoors for an indefinite period of time, they will weaken, become sickly and very likely die.

Image caption. A bonsai tree, especially one like this Japanese white pine, may not be kept indoors for longer than a few days at a time. Bonsai should be kept outdoors and only brought indoors for short periods of time.

I don't so much blame the owner who did not, but perhaps could have known better. I blame the seller for not making sure the person buying the tree knew enough to keep the tree alive.

As my readership is no longer exclusively local I often forget that I need to keep in mind a much wider audience than before. However there are limitations to this. There is NO substitute for joining a club or at least befriending an experienced grower in your area and tapping into their knowledge. For instance I have never had to be concerned about snow and ice (frost), if these environmental factors are considerations where you are then you clearly need to act appropriately.

#3 Don't make large cuts now

This statement might seem to contradict something I wrote in the first part, however let me qualify what I mean.

Image caption. To make the most of cutting back a large branch, do it during the active growing period as a lot of back budding will be simulated.

If you have been using a sacrifice branch somewhere on your tree and you don't need it anymore, cutting it now ensures that sap is not directed there in spring and therefore not wasted as it can be used elsewhere on the tree. You can also maximize the full growing season to come, to assist in the healing of the scar (although with some species which heal very quickly such as Chinese maples, you may be better off cutting large branches in the latter part of spring when sap flow has reduced or the resulting scar tissue, or cambium will bulge a lot).

However if you are in need of growth where you currently don't have any, and you don't want to graft, then it is better to wait till the tree is actively growing again before removing larger branches. The act of doing this will undoubtedly stimulate back budding on branches but even on trunks, provided they are not too old. This will allow you to fill these empty spaces with growth which otherwise may never have developed.

#4 Don't neglect weeding

Image caption. Weeds such as this winter grass, if allowed to establish will take over your bonsai container and worse yet, the seeds will spread everywhere.

Some maintenance tasks are boring, some are especially boring. Weeding has to rank pretty highly on the boring scale in my opinion. When you have a reasonably large collection of trees it is easy to neglect weeding though, putting it off till tomorrow. This will be a mistake though as some weeds will be seeding soon and your problems will become even worse.

My method is as a tree comes across my table, after I have worked on it, trimming and wiring it, I give the surface of the pot a good clean. This might include removing the remnants of fertilizer, pieces of off-cut wire and weeding it thoroughly. A little brush is also handy for removing the loose bits on the surface and leaves your bonsai neat and tidy.

If you find a lot of liverwort, you should also remove it but it is an indication of a worse problem. Your growing medium is too wet. Read more about this problem in the first part of this blog.

#5 Don't forget to take cuttings

Cuttings are one of the easiest and cheapest ways to increase the size of your bonsai collection. There are many advantages of growing bonsai from cuttings; the roots all emerge from the same point, the characteristics of the mother tree is carried over, if it's a fruiting tree the bonsai grown from a cutting taken will soon begin fruiting also, and many more.

I find that taking hardwood cuttings at this time of the year has proven to provide me with a high rate of success. Ensure you take cuttings from trees with desirable characteristics such as leaf shape and size, good bark etc. Use the appropriate hardwood rooting hormone powder or liquid and be sure to use sharp implements such as a grafting knife when you work with the cuttings. Buy cutting supplies here.

As a rooting medium you can use mixes of Groperl, Vermiculite, Peat or even the already mixed Professional Mix. You want something which drains quickly but retains moisture or the tender roots issued by the cuttings in spring will dry out quickly. 

Image caption. A clay container with completed cuttings. Each one could be used to create a new bonsai or as grafting material to improve the roots of more advanced trees.

Right, so there are some don'ts. I'm sure there are more and if you can think of one please share it with me. Thanks for reading.