Slowing down growth on a mature Bonsai

[dansai]

I thought I'd start this topic after a post in the General Questions and Answer thread where TimIAm posted a question regarding slowing down the growth on his tree and as he had where he wanted to maintain it. I've quoted the original post below

I have a Volkameria heterophylla (formerly Clerodendrum) that is currently in a mix of scoria, pine bark and premium potting mix. 3 years ago I moved it from a styrofoam box into a training pot and it is now at the point I want to slow down growth.

Aims I have:
- This thing can throw out an insane amount of roots in a single growing season. I want to slow down root growth.
- I no longer need this tree putting out long straight new growth and I want to avoid dense foliage growth. I want to avoid having to regularly thin out foliage "pads". I am happy with what I have
- I want to cut down on growth but I still want the tree to stay healthy

Appreciate if anyone can share wisdom on what I should be doing. This is the first tree I've got to reach this point where I am just satisfied with where it's at, so it's uncharted territory for me.

I'm thinking I would like to, and it may be useful to move it to an inorganic mix? But what should I then feed it to keep it happy? This tree has been with me for about 20 years now and would about that old.

It was then followed up with this

Just bumping this (my earlier post).

General question: Anyone know how to slow down growth on mature bonsai?

Basically just want to keep a mature tree in maintenance mode and happy and healthy.

I've tried searching this and other forums and Google. Can't find info I'm after.

There was this response by Per PF which sets out what I have heard before. That growing your tree hard (less water, fert, repotting and more sun) will slow its growth. This is true. And it can be a great technique to use with a tree.

General question: Anyone know how to slow down growth on mature bonsai?

I'm in noooooo way an experienced bonsai grower but since this is the internet my thoughts would be:

* Keep the fertilizer to a bare minimum. I've had plants do well for years without any at all..
* Don't over water, only when needed.
* Let it get proper pot bound.
* According to species, plenty of sun to keep leaves small.

Tim also stated he wanted to keep

a mature tree in maintenance mode and happy and healthy.

Shibui then replied and shared his knowledge and experience that I believe speaks to most growers of Bonsai. The above can be applied with very deep knowledge and practice to achieve a certain goal. Shibui's advice will ensure your trees health and vitality. There is some real gold in his response. Thank you Shibui for being some free with your knowledge and experience.

I've found that better trimming is a much safer way to maintain your mature bonsai.
Whenever resources become restricted trees have the ability to prioritise different areas or withhold scarce resources from certain parts in order to stay alive. Usually the apex is given preference and low branches are restricted or allowed to die off.

Restricting water is walking a knife edge. One hotter than anticipated day can be enough to 'finish' your tree. Each year the pot will be more filled with roots so less spaces for water. If you haven't estimated water requirements, especially through spring when demand is high, correctly that can be the end of your tree.
Repotting less often certainly restricts growth and some internationally known growers use this to maintain their bonsai but, again, you really need to know how to manage potted trees to do it successfully. After a few years the pot is so full of roots it is difficult to get water and nutrients into the pot. Unless you can compensate for the restricted water available, the trees suffer as the weather warms up through spring and summer. I find the health declining significantly in many of the bonsai when I don't repot regularly.
The vast majority of trees that have suffered or died from root rot or other root problems here have been those that were not repotted for some time.

Restricting nutrients is another way to manage growth but, like watering, I have found you can go a little too far. In the early days of growing natives I could not work out what fert was safe to use so did not fertilise at all. Most of those trees slowly died from starvation. More recently I tried restricting nutrients in maples and pines but have returned to regular light feed because I saw that branches, especially low or smaller ones, were becoming unhealthy or dying. There are some species that seem to be able to cope with reduced nutrients better than others. I've also been shown trees by people with little knowledge who have not fed the trees for many years. While those trees are still alive they are invariably in very poor health and do not have good shape or form.

As your trees grow you should also be learning more about pruning, trimming and the trees responses to those.
To maintain well developed trees:
Trim more often. Instead of allowing shoots to grow 4 or more pairs of leaves trim when the new spring shoots reach 1 or 2 leaves.
Remove all long internodes, even if that means removing some spring shoots completely. New buds will almost always form again.
Watch for multiple shoots or buds. Remove excess wherever there are more than 2. This is particularly important in pines and Japanese maples and in the upper parts of trees. Extra shoots can quickly thicken branches more than desired and result in ugly bulges.
Practice partial defoliation to allow light to reach shorter, weaker and lower branches. Without adequate light shaded branches weaken and die. Partial defoliation can be done while trimming spring shoots on opposite leaf species like maples. Cut the shoot and one of the leaves, leaving the other leaf to provide food for the tree.

As in most other aspects of bonsai you'll find many different ideas on how to maintain older bonsai. Absorb all the ideas but be cautious when applying new techniques to older trees.

I only have a few trees at the stage of refinement and maybe a couple at "maintenance" so I'm also keen to hear from anyone else with experience maintaining mature Bonsai

[melbrackstone]

My understanding is that the shallow container goes a fair way to controlling growth, and you're hoping that the branches will mimic the roots, in that they're ramified and healthy.
Definitely keep some fertiliser going, and definitely keep water up to it, especially as the heat starts to become oppressive.
Older trees need more careful management than younger ones, I've found. It's teaching me to be much less gung-ho with hard root pruning or big cuts.

[treeman]

I don't know if this was mentioned but if your tree has the full range of nutrients available to it at all times, you can adjust it's vigor with nitrogen. That means if you want to slow the growth you simply reduce the amount of N the tree is receiving. It means using a ratio of something like 10 - 2 - 15.
That is a K/N ratio of 1.5 or more. This might mean you need to juggle your different fertilizers until you achieve something like that. All the other points about repotting etc still apply but watering should never be reduced except with pines and a few other drought tolerant things perhaps.
Also, as your tree ages, it will produce more and more ramifications as a result of pruning. This will naturally reduce the vigor to each branch as well.

[TimIAm]

Thanks dansai for creating this thread. Thanks again shibui for the in-depth response.

(Since I started writing this in between breakfast, some of it has already been answered by treeman and melbrackstone. Thanks so much for great info coming in here!)

I have some follow up thoughts, appreciate if anyone can help:

Question 1: If I maintenance prune on a mature tree, if I try to maintain proportions, I'm concerned that this will reduce taper over time and cause inverse taper near foliage pads. Is the only approach rebuilding major branches and the top every few years as growth is inevitable? If I have a mature shohin, how do I deal with inevitable growth and keep it in proportion and not end up with a much larger tree over time?

Question 2: For a mature tree, would it be better to cut fertiliser and feed it something more nutrient focused? Can anyone recommend either a product or suggest what I should be looking for that is less 'high energy' and more nutrient focused?

Question 3: This may be an obvious (dumb) question, but will working towards a smaller pot size reduce the amount of the extra growth I need to deal with? My FIL who I learnt from used to keep everything in larger pots, shallow pots isn't something I've ever been exposed to.

[melbrackstone]

Question 1: If I maintenance prune on a mature tree, if I try to maintain proportions, I'm concerned that this will reduce taper over time and cause inverse taper near foliage pads. Is the only approach rebuilding major branches and the top every few years as growth is inevitable? If I have a mature shohin, how do I deal with inevitable growth and keep it in proportion and not end up with a much larger tree over time?

I believe that you have to let the shohin become a larger tree in time if you want to maintain its health. Regrowing after cutting back for taper is something I have had to do with my Crepe Myrtle, at least. They grow fast here in SE Qld. Your mileage may vary with other species.

Just a quick point, I wouldn't be constantly pruning throughout the year to maintain the silhouette. Give every tree a season or two to just grow, otherwise you may be forcing it too much.

Question 3: This may be an obvious (dumb) question, but will working towards a smaller pot size reduce the amount of the extra growth I need to deal with? My FIL who I learnt from used to keep everything in larger pots, shallow pots isn't something I've ever been exposed to.

Smaller pot sizes can help slow the growth, but you do need to be careful to not rush a larger rootball into a smaller pot if the tree isn't in perfect health.

The second question I can't answer.

[TimS]

Agree with everything Shibui said above basically.

There are always difficulties in giving generic advice for all species, but trimming, trimming and trimming again is the best and safest way forward.

I think it important to say that balance is key. Most of what we grow is apically dominant so the apex will always try to run away even with the standard pinching. It will throw more dormant buds up there, push more energy there and you need to keep it in mind so you remember to thin it out occasionally to keep energy in the low branches. A good way to combat this is to not let your trees grow to an absolute point, try to grow out a flatter apex, or at least divide it into 3 primary apical trunks to offset the energy being sent there. It won't fix the problem but it will help from my experience.

I would never, ever, try to use water restriction as a method to control internode length or growth habit. Too much risk and too little reward. I don't know about others, but I really deeply care about my trees and to try to walk a tightrope that risks the loss or big setback of my trees seems stupid.

Fertilising i wouldn't care to give generic advice for as it can really depend on the species you are growing. As a general rule though all my trees (exotics not natives) receive a good handful of blood and bone & a normal slow release mixed into the substrate at potting, and for that following season while it is still fresh in the pot i would err on the side of liquid feeding, and then the following season(s) until the next repotting i would look at a light pelletised dynamic lifter or such on the surface in addition to the liquid feed. I have had issues with maggots in my teabags though so i really actually don't do much of it. How much would depend on the level of refinement of the tree, the health of the tree, the natural growth habit of the tree etc.

Having said that a tree's genetic habit is far more powerful than our ability to control it via water/ fertilising and even trimming. You just kind of slowly cajole it in the direction you want over time.

 
More generalised to what i grow:

Japanese Maple: One of the hardest IMO to refine to delicate ramification

My example i always come back to is my oldest tree, the 62 year old Japanese maple. This thing STILL wants to throw 2-3 foot shoots in spring if i don't stop it by pinching the new buds out. So simply waiting for a tree to get older does not mean it will slow down its growth habit.

I don't tend to pinch to 1 pair of leaves as some practitioners advocate. A) because it's a royal PITA to try to delicately open each bud so early without damaging it and B) just simply because I'd prefer a healthy tree to anything else and JM is far more sensitive that Trident maple. So i pinch at 2 pairs as soon as is practicably possible at spring extension. This gives the tree a bit more photosynthetic surface area to balance up my pinching robbing it of 2 feet worth of photosynthetic area, and also keeps those 2 sets of buds in play for the future.

It never gets talked about, but i have discovered that Japanese Maple can grow susoba, or leaves without buds. It doesnt tend to be on every single bud, but i have noticed there to be occasionally the first pair of leaves to be slightly deformed and have a flat petiole. In this case i would count 2 pairs of leaves beyond this initial pair.

On mature trees I restrict any additional fertiliser other than what is existing in the pot already (slow release/blood & bone) until the foliage has hardened off, usually we'd be talking early to mid-October. The reason being that if i additionally fertilise before then, the leaves become excessively large and block light to the inner buds, and the internodes might become 7-8cm long. Useless for a tree you are trying to refine. Does it work? Yeah kinda, also yeah not really. The genetics play a much bigger part than the fertilising.

When they flush again in mid-summer i repeat the process of pinching to 2 sets of leaves. I would feed from October through to probably February every 2-4 weeks with liquid fertiliser depending on the individual circumstance of the tree. Again i want it healthy, i don't want it to be trying to turn back into a 10m garden tree.

In late summer (late Feb/ early March) i would go back in and remove any unnecessarily long internodes that had grown over the season to set up the following year's buds I want.

I NEVER, partially or fully defoliate Japanese Maple. When it gets too dense i would remove 1 of the pair of leaves across the outer canopy to let light into the inner recesses, but I've had too many problems in the past from trying actual defoliation that i won't do it again.

Best bet for ending up with a Japanese Maple with delicate ramification is to start with a tree that genetically has short internodes, small leaves and avoid material with coarse growth and large leaves. You have been warned.'

Additionally, after years of air layering maples off grafts, i would look for a well grafted tree of a cultivar with short internodes, and use that. Alternatively, i would try to grow cuttings of the cultivar and NOT air layer. I have overwhelmingly found that a good air layer is a rare thing indeed, and certain cultivars will just never be healthy and vigorous on their own roots. In time the graft will become less noticeable unless its' got a specific genetic trait like Arakawa has rough bark. In that case i would try cuttings or maybe an air layer to get the rough bark on the nebari/ roots as well.


Trident Maple

Shiiiiiiiz do whatever the hell you want. These buggers will grow like weeds, can be defoliated 3-5 times a season without ill health, and provided you give them some kind of nutrients over the season.

Seriously though, i don't bother pinching mature/ refined Trident Maple the way i do with Japanese maple just simply because they don't grow the internode length the way JM do. Let them run to maybe 3-5 pairs of leaves then cut back to 2 and that's about as complex as it gets for me and Trident Maple. I will do partial outer canopy defoliation (ie not full defoliation) at least 1 or 2 times a season. Best way to control them though is the pruning maintenance.


Chinese Elm
The boon of Chinese elm is the naturally short internode length. This means you are not fighting the tree the way you are with Japanese Maple.

Develop more ramification, develop more ramification, more ramification and when you think you have enough, develop some more ramification. Also hold of repotting too frequently. They are tough, super tough, like a pair of welding gloves they just take abuse and keep loving it. Generally, I don't advocate letting trees get too rootbound as you end up running into watering issues, but Chinese Elm is my exception to the rule. They will be happy enough if the pot dries out as long as you do give it a good thorough soak as well.

I let the new shoots go to maybe 5 leaves (sometimes I'm slow and lazy and they get to 7) before cutting back to 2-3 depending which way i want the new shoot to grow. Any more than about 7 leaves and i start getting thickening of last year's growth and that starts to affect the very delicate ramification.

Repeat with each flush and in a few short years you have delicate ramification. Dead easy!




Ginkgo

These are weird ones and very slow growing, they grow in both alternate and whorl patter which can get a bit confusing. I don't have any super into refinement because that's not really how Ginkgo grows. There is no such thing as fine ramification with Ginkgo. If you are growing in flame shape just encourage more and more buds as they appear, keep them growing up and out (in that order) and just remove any buds/ branches heading into the interior of the tree.

The new buds appear immediately quite thick, can easily be pencil thick straight out of a dormant bud, so yes forget fine delicate ramification. I cut back new shoots at 3-5 leaves back to 2 just because there is usually no sense in letting them go any further than that as a mature tree. Its just going end up being 1ft long dead straight shoot the thickness of a pencil so chop it.

If you are trying for more of a tree shape.....good luck. They don't really behave like that from my experience, but if you grow in the flame shape once you get some established thicker primary branches, you do get the sense of the secondary branches being thinner and the notion of ramification there.

Honestly, grow them as a flame, keep cutting back to and outward facing bud at 2-3 buds, remove crossing shoots and let it fill itself in over time and you'll get a spectacular flame.

[GavinG]

Interesting discussion, thanks all.

For me, the health of the tree is paramount, then you do whatever the tree lets you get away with. A marginally vigorous tree will lose inner and lower branches. That's it.

No-one has yet mentioned sequential pruning/trimming/pinching - doing the lower branches first then the stronger, upper branches harder, later. You always need to direct the growth, and balance it - endless ramification just for the sake of it can weaken and unbalance a tree easily, and when spring comes, you find the lower branches have died, and your design has gone.

Trees stay healthier for me if they have some time in the year when they grow freely - constant nagging discouragement has the same effect as it does with children.

I've noticed particularly with Eucs that they are rampant growers when young, in larger pots, but when they are mature in bonsai pots they are no-where near as confident. I pot them deeper than I did, and take them up a pot size every two or three years - they thicken that quickly! Acacias also need deeper-than-usual pots.

This may sound heretical, but don't get too hung up on "your design", particularly with natives. When they are young, let them grow wild, then cut out the boring bits. Over a few years, you will need to harmonise the bits you keep with last year's work, and the years before. You "evolve" a tree, rather than design it, and what that tree naturally does, often adds up to something way more interesting than what you would have designed.

The title of this thread, "Slowing down growth on a mature Bonsai" suggests the need to cling to a particular form that the tree has now taken - natives grow so fast, and have so many possibilities, that the "design" keeps evolving - much more entertaining!

Thanks for the discussion,

Gavin

[GavinG]

Oh, and I keep my JMs in near-full sun - no mildew, but the leaves look tatty by late January. I will happily defoliate them then for a good autumn show of colour. They are well fed.

Gavin

[TimS]

Oh, and I keep my JMs in near-full sun - no mildew, but the leaves look tatty by late January. I will happily defoliate them then for a good autumn show of colour. They are well fed.

Gavin

Totally agree with this, up to a maximum of ~35 degrees C. Once we go over that here in Melbourne my JM get protected, previously under a patio or inside the house but now in the shade house. More importantly, for JM of any size or refinement is to protect them from high wind, especially hot and dry wind. If we get a wind warning my JM get protected simple as that.

Unrelated to mature bonsai growing, but I would absolutely not recommend growing Shindeshojo at all due to it's insane propensity for powdery mildew. I've had trees come into my garden with powdery mildew but never had a straight species or any other cultivar really get powdery mildew that didn't already have it under my care, but my god it's like Shindeshojo is a magnet for it. I have now 100% given up on growing it as a bonsai subject despite it's advantages for spring colour.

[treeman]

=TimIAm post_id=301728 time=1696114835 user_id=11048]
Question 1: If I maintenance prune on a mature tree, if I try to maintain proportions, I'm concerned that this will reduce taper over time and cause inverse taper near foliage pads. Is the only approach rebuilding major branches and the top every few years as growth is inevitable? If I have a mature shohin, how do I deal with inevitable growth and keep it in proportion and not end up with a much larger tree over time?

You don't ''rebuild'' major branches. You thin to a good basic structure and remove everything else. Which means if you have 5 sub-branches all extending out to the same length, you might remove 2 or three and still have the remaining ones making up the original outline of the silhouette. That way the tree continues to develop without becoming congested and thickening where you don't want it to. The tree will continue to grow so it's impossible to keep it the same size forever but you can delay the process for a long time by continually replacing the leaders. That is basically what bonsai is.

Question 2: For a mature tree, would it be better to cut fertiliser and feed it something more nutrient focused? Can anyone recommend either a product or suggest what I should be looking for that is less 'high energy' and more nutrient focused?

Fertilizer IS nutrient. As I mentioned, it's the N you want to reduce. Traditional fertilizers like meal cakes are ideal. There are many recipes.
Here is one.... viewtopic.php?f=12&t=21156&hilit=cakes
Omitting the blood and bone will reduce the N further.

Question 3: This may be an obvious (dumb) question, but will working towards a smaller pot size reduce the amount of the extra growth I need to deal with? My FIL who I learnt from used to keep everything in larger pots, shallow pots isn't something I've ever been exposed to.

In a word, yes.

[melbrackstone]

I have a Volkameria heterophylla (formerly Clerodendrum) that is currently in a mix of scoria, pine bark and premium potting mix. 3 years ago I moved it from a styrofoam box into a training pot and it is now at the point I want to slow down growth.

Aims I have:
- This thing can throw out an insane amount of roots in a single growing season. I want to slow down root growth.
- I no longer need this tree putting out long straight new growth and I want to avoid dense foliage growth. I want to avoid having to regularly thin out foliage "pads". I am happy with what I have
- I want to cut down on growth but I still want the tree to stay healthy

As an aside, I guess you'd like specific Volkameria info. I grow them here in Qld, and yes they are very strong growers. I've slowed mine down by not growing them in water. Same with swampies. If you sit them in water they'll just keep throwing out strong roots and top growth, and it'll seem like you'll never be able to control them. By not sitting them in water I've been able to teach them to grow like normal plants. As I mentioned about growing the top to mimic the roots, if you're getting a pot full of thick strong roots in one season, you'll also be getting gross and heavy growth at the top.

[dmattar]

Thanks dansai for creating this thread. Thanks again shibui for the in-depth response.

(Since I started writing this in between breakfast, some of it has already been answered by treeman and melbrackstone. Thanks so much for great info coming in here!)

I have some follow up thoughts, appreciate if anyone can help:

Question 1: If I maintenance prune on a mature tree, if I try to maintain proportions, I'm concerned that this will reduce taper over time and cause inverse taper near foliage pads. Is the only approach rebuilding major branches and the top every few years as growth is inevitable? If I have a mature shohin, how do I deal with inevitable growth and keep it in proportion and not end up with a much larger tree over time?

Question 2: For a mature tree, would it be better to cut fertiliser and feed it something more nutrient focused? Can anyone recommend either a product or suggest what I should be looking for that is less 'high energy' and more nutrient focused?

Question 3: This may be an obvious (dumb) question, but will working towards a smaller pot size reduce the amount of the extra growth I need to deal with? My FIL who I learnt from used to keep everything in larger pots, shallow pots isn't something I've ever been exposed to.

1)

You build the “new” branch by encouraging inside branches to form. That way when your main branch line or leader gets too fat, you have a sub branch to cut back to for taper. If you have already built some ramification on this branch, you won’t be starting from scratch. You are more likely to get inverse taper and knobby ends on branches with a hedge prune compared to selective pruning at some point in each growing season. Partial defoliation or other similar techniques help to balance the tree overall and get inside shoots to develop.


2)

Try Japanese style fertiliser cakes like Treeman recipe. Other ones I’ve seen are 4 parts cottonseed/soybean meal, 1 part blood and bone, 1 part fish meal and some flour with fish emulsion diluted in water so you can form a ball. Timing is also different for more mature bonsai. Some don’t fertilise until after the second flush of growth has hardened in mid summer and then fertilise very heavy in autumn. Multiflush pines can be fertilised from late winter up till one month before decandling.


3)

Yes but not too shallow with some species. With volkameria, you are more likely to get weak health in the cold weather and yellowing leaves if significantly underpotted. And underpotting is more likely due to their rampant root growth.