Combatting reverse taper and tree vigor

Lou T

Mame
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I have a prickly ash (Zanthoxylum clava-herculis) tree in ground that I hard pruned in March. It’s a native here to the south east and relevant to the Timucua Native American culture here in NE Florida so I figured I’d experiment with this one as it already had a natural trunk scar and it’s conveniently located in my back yard.

I learned the tree grows vigorously during the growing season and as a result, some major reverse taper is developing as the leaders I selected fatten up. Is there a way to combat this? Should I remove the mass and select another leader?
 

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sorce

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You can trim it down, I would do this now while it can still heal it this year.

Capture+_2019-06-18-06-43-03.png

But....
Have you dug down at all to find roots?

Seems iffy on the basal action.

Sorce
 

Lou T

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You can trim it down, I would do this now while it can still heal it this year.

View attachment 247882

But....
Have you dug down at all to find roots?

Seems iffy on the basal action.

Sorce
Thanks for the reply, Sorce. I know there are roots directly below the soil as I uncovered the tree enough when I pruned it so that there would be a short distance between the basal flare and new shoots. Though in my experience with this species, the trees tend to grow few, fat roots - albeit an interesting touch as the binomial name suggests, the roots are a vibrant yellow hue.

I’m going to do work on it this weekend and follow your rendition. Thanks again.
 

sorce

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Nice. I had to hack my yard one last fall cuz someone was feeding the birds amd they kept shitting all on my garbage cans....
Crazy how much that effer grew! Six foot shoots already and inch thick.

You will likely already be able to identify the heal line and just carefully trim right back to it....then only damage the new healing part if it certainly needs it to keep your line right.

Sorce
 

Adair M

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It has a compound leaf and long internodes. Not the kind of qualities that make good bonsai. Especially small bonsai. You would be most successful going for a large tree style rather than a small tree.
 

Forsoothe!

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This seems to be proceeding back-asswards. The roots have some capacity to grow the top, in proportion to the size of the roots. The smaller the top is in proportion to the roots, the more that growth is going to be expressed as water-sprouts. That just aggravates the natural tendency of this species to have long internodes, giving you the worst of both worlds. You are growing a potato with telephone poles. I don't think that's what you're after...

The only way to divert growth into shorter internodes/earlier & more ramification is to pinch the leader, early in the process, before it grows that long internode. That's a double-edged sword here, too. It will respond by putting out clusters of buds, like 10 or 20 in a cluster. All of these responses are perfectly normal because the roots are grossly out of proportion to the top.

A better strategy would be to lift it and put it in a ~large-ish (bigger than typical) pot to reduce the imbalance of roots-to-top. Pinch the leader every time and place where the internode reaches the length you want. You will still have too many twigs/branches sticking out all over the place, but hopefully some will be located well and others will be sacrifice branches. NOT sacrifice branches in the ordinary use of growing part of the trunk, but in this case useful to use up surplus root energy, so some sacrifice branches can be telephone poles as long as they are well-placed, AKA not sticking out of the front or where the scar will be counter-productive. After the basic architecture is set you can sink the pot and get some more vigorous growth, but you will still need to short-cut long internodes by pinching leaders. The species has long internodes and will forever want to revert to type.
 

Lou T

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It has a compound leaf and long internodes. Not the kind of qualities that make good bonsai. Especially small bonsai. You would be most successful going for a large tree style rather than a small tree.

You’re absolutely right though I’d still like to give it a shot. Right now after all it is one tree growing amongst many others of its kind and I enjoy looking at it once in awhile.

This seems to be proceeding back-asswards. The roots have some capacity to grow the top, in proportion to the size of the roots. The smaller the top is in proportion to the roots, the more that growth is going to be expressed as water-sprouts. That just aggravates the natural tendency of this species to have long internodes, giving you the worst of both worlds. You are growing a potato with telephone poles. I don't think that's what you're after...

The only way to divert growth into shorter internodes/earlier & more ramification is to pinch the leader, early in the process, before it grows that long internode. That's a double-edged sword here, too. It will respond by putting out clusters of buds, like 10 or 20 in a cluster. All of these responses are perfectly normal because the roots are grossly out of proportion to the top.

A better strategy would be to lift it and put it in a ~large-ish (bigger than typical) pot to reduce the imbalance of roots-to-top. Pinch the leader every time and place where the internode reaches the length you want. You will still have too many twigs/branches sticking out all over the place, but hopefully some will be located well and others will be sacrifice branches. NOT sacrifice branches in the ordinary use of growing part of the trunk, but in this case useful to use up surplus root energy, so some sacrifice branches can be telephone poles as long as they are well-placed, AKA not sticking out of the front or where the scar will be counter-productive. After the basic architecture is set you can sink the pot and get some more vigorous growth, but you will still need to short-cut long internodes by pinching leaders. The species has long internodes and will forever want to revert to type.
It sounds like I need to start over. I may just cut that bulge responsible for the reverse taper and constantly prune the new leader. It’s growing so fast right now so I imagine the wound will heal in a short time. I think you’re right in lifting it. I let the shoots gets fat thinking it would take time to achieve girth though that definitely doesn’t seem to be the case. Thanks for the guidance.
 

Leo in N E Illinois

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@Lou T
"Reverse taper" is not something you need to worry about, this is naturally lumpy and bumpy species. If you are planning on increasing the diameter of the trunk by a third or more you can "grow it out of" reverse taper.

Besides, once the bark and spines form, lumps, bumps and weird shapes will add rather than detract.

I agree with Forsooth that you should put it at least in a large nursery pot to slow down it's growth. I WOULD NOT pinch new growth and new leaders constantly. I would prune the shoots only 2, at most 3 times a year. You need the tree to burn off excess energy. Let everything grow out. Then prune back to maybe just one additional internode, for all the keeper branches. If the internode is too long, prune all the new growth off. The next flush should be shorter, with shorter internodes. When pruning, the keepers to just one new internode length, prune the furthest node off the sacrifices, leave no apical buds intact. If you do the sacrifices will take over the resources and a weak keeper could get lost.

But let it grow as much as 6 or more feet tall, then prune back to just a short little node.

This will help burn off the excess vigor. Putting it in a pot will help slow it down too

I had to read up, interesting chemistry for this plant. Possible "cure" for MRSA drug resistant staphylococcus.
 
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