Maple back-budding

[Andrew Legg]

Hi All,

I have a question that I feel real dumb asking, but I am gonna ask all the same! I have just got into maples, and in particular Chinese/Tridents. My question relates to the nature of back-budding. If I leave a branch to grow out, it gets leaves in pairs, alternating horizontal/vertical/horizontal/vertical etc etc. I know that in the axils of each leaf are dormant buds, and that if you pinch out the growth at the end, the last set of buds seem to activate and grow out. So the real question is: If I pinch back continuously, will I get buds activating anywhere else on the branch (i.e. buds that are not in existing leaf axils)? I think the answer is yes and that they are called adventiscious buds, but I am not sure.

And some more questions:

I am struggling to get short internodes and they seem to get longer and longer the further out the branch grows. Should I be letting each branch grow out to a certain number of leaf pairs and then trim back to one or two pairs, or should I pinch out the growing tips after development of the second pair of leaves?

My trees get a few hours of morning sun and then are shaded by a big Hibiscus in the afternoon. I have a really small garden so there are not too many options for alternative locations as my pines, junipers and olives take all the sunniest positions.

Any advice would be much appreciated.

Cheers,

Andrew

[63pmp]

Hi Andrew,

You will only ever get back budding on a trident at a leaf axial, or node, even is the branch is very old. In theory you may get a bud form from an adventitous bud between nodes, but I have never seen this with any of my tridents, and I don't think it happens.

Regarding node length, two factors are involved here.

Firstly, the terminal meristem at the tip of the shoot releases hormones which stops secondary buds forming, it has nothing to do with node length. Pruning it off does allow buds at lower nodes to develop, usually at the next node down.

Node length is determined by hormones released from newly developing leaves, and how fast cells are reproducing in the stem. The stem only stops elongating when it becomes woody, which takes about 2 weeks. If you remove the leaves at a node below the apical meristem the section of stem between this node and the one below will stop lengthening. You can do this as often as needed, with as short a node length as you want. Secondary buds will not develop until the apical meristem (or bud) is removed) This process weakens a stem considerably as it stops transpiration flow bringing nutrients up the stem from the roots, the stem becomes dependent on phloem supply, and hence weaker.

Another way is to pinch of the apical meristem as it emerges between the first set of leaves straight after bud burst. Another is to allow 4 sets of nodes (leaves) to grow unhindered and remove the top 2.

Stems always have a few small discrete buds at their base, if the nodes are too long, cut back (at the right time) and leave a stub, hopefully a new bud will develop from here.

Hope this helps

Paul

[MelaQuin]

Thanks, very helpful.

[Andrew Legg]

Hey Paul,

Thanks for the info! Which technique would you recommend as being most effective, + 4 -2 or the early pinch out? I guess another option to shorten internodes would be to do a graft? Do you think this is more effort than it is worth?

Cheers,

Andrew

[stymie]

I pinch out the lead as soon as it emerges from the second pair of leaves on young Acers. Even at every pair of leaves on mature material and at the apices of all. This creates a twiggy, close knit tree which is desirable.
The semi-shade location sounds good to me. If you increase potash at the expense of nitrates, this too will help to keep the internodes shorter.

[Andrew Legg]

Thanks Stymie. I understand the end result to be better, but does the branching take a lot longer to get into shape this way? I have all the time in the world, so am in no rush to get to the "end" result. Sounds like all the branches should go back to the first or second pair straight away and work from there. What about the mention that pinching the growing tips weakens the branch (from Paul's comments)? Does it not weaken it too much if you catch it early?

Thanks

[stymie]

After initially growing the trunk, my pinching out the shoot at every leaf pair can be done three times during a good growing season here. Two shoots become four become eight if you get the drift. Only twice pinching in a poorer season will still give four shoots where there was only one to start with. Without quoting scientific reasons, I haven't noticed any weakening unless that is what causes the leaves to get gradually smaller. It becomes necessary to select only the shoots which face out or down when the canopy gets too dense. Oh, don't you just love these Acers?

[Istari]

Oh, don't you just love these Acers?

I do, I really do

On the topic i know you've said to decrease the node length increase the potash & hold back on the nitrates. If you were just after the growing season is it still best to keep up the nitrates?

Another question, ive got some new seedlings this spring was just wondering if using this technique short term would be a good way to encourage trunk thickness longer term?