Hardening off nuance question with examples

Obviously, understanding when ‘the first flush of growth hardens off’ is really important in bonsai. I’ve heard Ryan explain it a number of times, and even talk about how he has already ‘explained it a number of times’ :smile:

I’m trying to understand what defines ‘the first flush’. For example, in wanting to prune back on a deciduous branch to improve ramification.

I have uploaded ‘example’ deciduous branches with light green leaves obviously being ‘unhardened’ growth (and the growing tip) and dark green being hardened off growth. Is this “sufficient” for ‘hardening off’?
(or, this for that matter)
Or, does one need the entire leaf structure to harden off out to the growth tip before the branch has ‘hardened off’

So, is the ‘first flush’ that needs to harden off the first pair of leaves, or the whole ‘branch/shoot’ of leaves? or what? Thanks for any assistance,


@Brady, Excellent art work! Visual aids are always helpful haha. Sometimes this will depend on the tree itself, for example, I believe a larch’s terminal bud is almost always soft and fleshy. The “hardening off” is the cuticle forming on the leaf to prevent excess transpiration (water loss) and is usually quite easy to distinguish, as in your pictures. I would wait until all new growth has formed a cuticle as the tree is in an “energy negative” at this stage, spending energy on hardening the cuticle on every leaf. As far as the growth tip (terminal bud?), I’m not sure; hopefully someone else can weigh in.

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Tonight’s stream is all about deciduous pruning so I’ll guess we’ll get our answers there.
When Ryan pruned the hedge maple last year there were new growth occuring all over the tree and that growth should be apart of the first flush since we’re pruning to induce a second flush. Not sure tho, not sure at all :joy:
I also believe I heard @ryan mention hardening of after four weeks in the broadleaf stream, all other articles I’ve read has said that trees usually hardens of after 6-8 weeks. I’m eagerly awaiting tonight’s stream popping down in the archive!
Also remember what @ryan are telling us to do, speak bonsai. We do work when the tree is saying “I have enough to sustain and add”. That’s telling me that we have growth were the cuticle has formed and new growth that excess energy is putting out.

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@Kendall…this post might be worth noting and perhaps addressing in tonight’s stream since it is on topic and timely and has such good illustration. It could then be archived as it is a question that comes up frequently. There could actually be a future for a FAQ, or “most common questions” forum pin, for well answered posts to commonly asked questions…similar to the must watch video pin…just my 2 cents.


Thanks, all!! A few followups.

  1. I recall Ryan mentioning that the terminal bud will often (always?) remain ‘soft’ when the flush hardens, so I’m less concerned about that issue as I think he stated clearly that that doesn’t define whether the first flush has hardened or not.

  2. I’ll definitely be catching tonight’s stream, though I might have to wait until the archive.

  3. I guess part of my question is, is the first flush ‘the first pair of leaves’ or an entire push of growth that ends when the plant ‘pauses’? I believe the latter (though, perhaps there isn’t a “pause”?). In my drawing, I was asking if it was the former – if those first leaves start to harden, is that enough to say the flush has hardened – I’m betting not (though I would assume most of the branch will harden soon after the first set of leaves darkens). I don’t have the horticulture background to always understand a term like ‘flush of growth’ without more context/explanation…though I’m learning tons! :slight_smile:

I’m watching all my plants’ growth much more closely this spring thanks to Mirai, so could be this will be more clear in reality than I am concerned it will be.

Thanks all,

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@Brady this link has the info you are looking for, Jonas does a great job showing with pictures.

Cutback and wiring on a semi-cascade ume

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@SatoriBonsai I appreciate the effort to help and I enjoy Jonas’ blog.

I don’t, however, see how that link answers or relates to my question above. Ryan did, however, answer my question in the aforementioned stream…I think about 30 minutes in or so. Thanks to Kendall for asking on my behalf and everyone here for trying to help.

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Understood @Brady , sorry the blog did not answer your question specifically. I was just hoping that seeing pictures of someone cutting back to hardened off growth to create structure would help with the question of what hardened off growth is. The first few sets of leaves on a long shoot have grown a hard enough cuticle so Jonas cuts back to them, but I see how the blog could seem off topic. Glad Ryan answered your question with great detail

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Ahh… You mean I should look at the photos ‘and’ read… not just read… :). That seems really obvious now, I just made an assumption you were suggesting text. Thanks, I’ll take a glance at the photos for some additional context.