After I published this video: Bonsai Care – How to prune your Bonsai tree, also labelled “10 reasons to prune your bonsai”, I received and answered the following questions:
Question: Is pruning time any different for an indoor tree? Or is autumn, winter, spring, etc the same?
Dave’s answer: For indoor tropicals like ficus, sageretia theezans, carmona, any time of year. But if you are root-pruning it in spring, don’t prune the branches at the same time.
Question: I’ve never really taken care of my Bonsai but now starting. Is it safe to cut hard back to allow leaves to regrow? It’s a Ficus, kept indoors. In need of fresh soil and food!
Dave’s answer: If the ficus appears in good health then in general you can prune it prune it back hard any time of year. Don’t prune the roots at the same time though.
Alternatively if you decide to repot it now, don’t prune the branches until it has completely recovered from the repot. You’ll know when it has recovered because it will push out new leaves and when these have fully extended and hardened, probably after 2 months or so, you can then prune the branches.
“If you are root-pruning it in spring, don’t prune the branches at the same time.”
Dave Bluesky
Question: How long are we leaving sacrifice branches in place? Years? Months?
Dave’s answer: It depends on the bonsai size. If it’s a tiny mame or a shohin probably 6-9 months or absolute longest 1 year, after that the scar would cover half the circumference of the trunk. A bigger tree, or a shoot that you’re growing on for a few more years, then you could probably keep a sacrifice branch for a couple of years and let it feed that trunk good and fat!
Question: So my bonsai is growing at the moment in January and I was wondering if it was ok to prune still. it is a Chinese elm and it is an indoor bonsai.
Dave’s answer: The so-called tropical species like ficus or carmona or sageretia, you can prune any of these in January, no problem, while they’re actively growing. A Chinese elm, if kept indoors, can be treated like a tropical species because it is only “semi deciduous”; if it doesn’t get cold then it doesn’t drop its leaves. So yes you can prune in now in January.
However, in the long run, it would be healthier for the elm to give a couple of months of cold each winter so it can go dormant and rest for a couple of months each year. For some people I realise this may not be practical if you don’t have a secure outdoor space. I keep all my elms outside, except two which are tiny, 6cm (2 inch) mame size.
“Bonsai can be an artistic expression of the continual struggle between, on one hand, the harsh elements of the environment, and on the other hand the need to grow and reproduce.”
Dave Bluesky
Question: I am new to bonsai and I have a few questions about pruning. I have a Chinese Elm that I am wintering at a nursery and an Australian Brush Cherry that I keep indoors. First, should I do a major pruning twice a year(winter and summer) or more frequently? I read that since the brush cherry is a hedge-like tree it needs to be pruned often. Second, my brush cherry just had a mealy bug infection that was successfully treated last month. How long should I wait to prune it? I already did a pruning in November. Lastly, I read that “you should never prune all the new growth at once”. What does that mean? Can I harm the tree if I take off too many leaves? After you have pruned a branch to two leaves, do you have to let the next two branches grow and prune them back to two leaves, meaning that you need to let the tree get gradually bigger? Is it possible to keep the tree the same size or do you always need to let it grow slowly?
Dave’s answer: I normally give straight hortucultural answers to these questions but in this case I think it might help to think of bonsai on a meta level: what is it all about underneath the branches, roots and pruning decisions. Bonsai can be an artistic expression of the continual struggle between on one hand the harsh elements of the environment, and on the other hand the need to grow, flower and reproduce. This is represented artistically by maintaining a balance between beautiful harmony and the visually jarring.
So back to your questions: the Chinese Elm is very resilient and could easily take pruning 5 or 6 times a year, as if you are the “harsh environmental elements”; however, you also need to let it grow out sometimes and let branches break out of that beautiful harmonic silhouette that you create when you prune it. So twice a year, summer and winter, is really the best pruning regime in my opinion. You do need to let trees grow out somewhat to manufacture sufficient energy (photosynthates) in the leaves.
You can prune back all the new growth on a vigorous plant or tree. If you see it is vigorous then it is also (generally speaking) in good health. But if it’s not doing so well, don’t prune it; give it some TLC and keep a close eye to avoid reinfestations.
When pruning, yes, prune back branches to 2 leaves then prune back the resultant secondary branches to 2 leaves, then tertiary and so on. That’s how you get beautiful ramification, a realistic looking twigginess to the tree. Back to the “balance” point. You the artist have to make the ongoing judgement between a realistic, natural looking tree and a small size/shape; that is the balance between the organism’s need to grow to absorb light, against the forces of nature impeding its growth.
I also recommend this video on essential bonsai health – this one is purely horticultural: https://youtu.be/a_vYCvQL5iE
Blue Sky Bonsai 