Failed Root Grafts

AndyJ

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Hey folks.

I wonder if you can help me with something? I’ve got a Deshojo shohin sized maple that I’ve had for about 5 years. After it’s first repot (2016) I found one side had a really poor nebari - no roots on it at all - so I decided I would get some JM seedlings and run through some thread grafts and get some roots placed on the blank side. So, roll round to 2017, and seedlings in hand, I drilled three holes through the trunk, pushed through the seedlings, wired the graft whips up so they pointed to the sun, and potted up. The whips leafed out and grew a couple pairs of leaves and then died.

So, in 2018, I repeated the process again - and the same thing happened. The whips all died.

I skipped last year as I wanted to leave the tree to have a rest from repots and I just let it grow. And then this year (2020), I thought I’d have another go. And the same thing happened - all three whips died.

What am I doing wrong? Since 2017, each time I’ve tried I’ve had to drill my holes slightly bigger - I want to try these grafts again but if I don’t get it right in 2021, I’m going to end up with three big holes at the root line and it’s going to ruin the tree.

This is what I do.

- Slip the graft through the hole,
- Push a tiny piece of stick underneath to make sure the whip is in contact with the parent (making sure not to crush the whip)
- Wire the whip upwards so it faces the sun
- Put some putty around the wound.
- Finally, I cover the whole surface with chopped sphagnum moss. That’s it!

But they all died again!

I thought my technique was ok as I’ve thread grafted two new branches into this tree and they’ve taken. I’m wondering now if I need to plant the parent and the whips in a bigger pot so I can get them planted deeper - could that be it?

Am I missing something? I thought this process would be fairly straightforward!

Thanks all.

Andy
 

0soyoung

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I would guess the death of the threads was due to the bending. Japanese maples seem to be prone to this when they are leafless and dormant. I've not had troubles within a period of a few days around the time of leaf drop, but otherwise bending a dormant sapling/stem results in a xylem-clogging CODIT reaction.

Secondarily, thread grafting is an extremely poor way to affect root grafts. The basic way a thread graft works is that the thread thickens so that the hole becomes a tourniquet. This cuts off the roots from their supply of carbohydrates and auxin which would cause their death, eventually. Apparently, some have succeeded doing this, but it can only happen if the mother tree's growth closed the entrance hole and somehow affected fusing with the scion's cambium. Hard to believe, IMHO, but maybe so. I remain a little skeptical that anyone has succeeded with threaded root grafts.

Short version = root grafts must be approach grafts. Bend the scions when they are in leaf or just dropped leaves a few days ago.
 

Shibui

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I have had some success with thread graft for roots but sometimes the exit fuses first and I get new trunks instead of new roots.
Approach grafts are also not 100% success. Some take a couple of years to fuse then the pruning cut can be large and takes years to heal over.
Partial layering is an alternative - remove a strip or patches of bark where roots are required, treat with hormone, pack sphagnum and cover to keep damp. New roots will take years to catch up to the established ones but this does not leave scars on the nebari.

How thick are the seedlings you are grafting with? Really thin ones are harder to work with and are fragile. I have not actually wired thread grafts up. Just gently tie the trunk to grow upward or thread it through the branches of the tree and let the tree support it.
I also wonder whether the sphagnum may be keeping the roots too wet and causing some problems? I have not found sphagnum to be necessary when using live roots, only to develop new ones from scratch.
 

AndyJ

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I would guess the death of the threads was due to the bending. Japanese maples seem to be prone to this when they are leafless and dormant. I've not had troubles within a period of a few days around the time of leaf drop, but otherwise bending a dormant sapling/stem results in a xylem-clogging CODIT reaction.

Secondarily, thread grafting is an extremely poor way to affect root grafts. The basic way a thread graft works is that the thread thickens so that the hole becomes a tourniquet. This cuts off the roots from their supply of carbohydrates and auxin which would cause their death, eventually. Apparently, some have succeeded doing this, but it can only happen if the mother tree's growth closed the entrance hole and somehow affected fusing with the scion's cambium. Hard to believe, IMHO, but maybe so. I remain a little skeptical that anyone has succeeded with threaded root grafts.

Short version = root grafts must be approach grafts. Bend the scions when they are in leaf or just dropped leaves a few days ago.
Oh ok, thanks Oso.

I set the grafts each year when I was repotting, just before buds were breaking - I never gave it a thought that gently bending the trunks could have an adverse effect. That kind of ties in with my experiences doesn’t it?

Surprised that thread grafting isn’t a good way to effect root grafts - I thought it would be neater! 😂 So approach grafting is the best road to take then. So I’ll try approaches next spring and see how I get on. What would you advise I do with these holes I have drilled? Should I fill them with a hardening compound? Or will it be ok to use these as my approach grafting points - as long as the trunks on my new seedlings are bigger than the holes?

Thanks again.
 

AndyJ

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I have had some success with thread graft for roots but sometimes the exit fuses first and I get new trunks instead of new roots.
Approach grafts are also not 100% success. Some take a couple of years to fuse then the pruning cut can be large and takes years to heal over.
Partial layering is an alternative - remove a strip or patches of bark where roots are required, treat with hormone, pack sphagnum and cover to keep damp. New roots will take years to catch up to the established ones but this does not leave scars on the nebari.

How thick are the seedlings you are grafting with? Really thin ones are harder to work with and are fragile. I have not actually wired thread grafts up. Just gently tie the trunk to grow upward or thread it through the branches of the tree and let the tree support it.
I also wonder whether the sphagnum may be keeping the roots too wet and causing some problems? I have not found sphagnum to be necessary when using live roots, only to develop new ones from scratch.

Thanks Shibui. So I’ll have to keep a close eye on approach grafts too then to make sure they don’t get too thick?
 

Dav4

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I've placed many root grafts, both threaded and approach, and I'd have to say that probably 60-70% take regardless of technique. Mind you, my experience is all with tridents and not palmatums. I've found that palmatums readily ground layer, though, so I'm more apt to go that route if the roots need a lot of work.
 

AndyJ

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I've placed many root grafts, both threaded and approach, and I'd have to say that probably 60-70% take regardless of technique. Mind you, my experience is all with tridents and not palmatums. I've found that palmatums readily ground layer, though, so I'm more apt to go that route if the roots need a lot of work.
Thanks for the feedback Dave. I wonder if tridents respond differently to Acer Palmatum then? When you did your roots with a thread graft, did you do anything different to the way I described how I did mine?
 

markyscott

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AndyJ

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No ... basically the same procedure.
Thanks Dave. One last thing. Did you replant the trew in a shallow pot after applying the graft? Or was it a deeper one?
 

AndyJ

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So, @AndyJ, did your root grafts really fail or did you just assume the roots did because the leaf side of the tread died?
Ooh good question Oso!

To be honest, with the first two years years, I noticed dieback creeping down the trunks from late spring / early summer and each whip went brown. When I came to repot, I checked the whips and could see that each one had died. As far as the root grafts done this year are concerned, I have seen the same tell-tale signs with the whips dying back but as yet, I haven‘t checked the roots. I might be in for a surprise when I repot next spring!
 

AndyJ

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Hey folks. Well I’m pretty sure the root grafts have failed on my Deshojo again - two years on the trot. I’m determined to try and get this right as the tree doesn’t have a very good nebari and needs some assistance. I wonder if part of the problem is that its planted in a bonsai pot. Do you think planting it in a box so I can get it deeper would make a difference? What do you think? I’ve got 6 JM seedlings and I’m ready to start grafting!!
 

0soyoung

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Is it possible for you to post a pic or two of the present situation, both of the thread entrance side (where you are trying to add roots) and the exit side (where the threads would have leaves)? IMHO, this would help to get you some concrete advice/help.
 

AndyJ

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Is it possible for you to post a pic or two of the present situation, both of the thread entrance side (where you are trying to add roots) and the exit side (where the threads would have leaves)? IMHO, this would help to get you some concrete advice/help.
Hi Oso. Yes will do. I’ll get some pictures tomorrow - I think our temperatures are set to rise above freezing here tomorrow.
 

Dav4

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Hey folks. Well I’m pretty sure the root grafts have failed on my Deshojo again - two years on the trot. I’m determined to try and get this right as the tree doesn’t have a very good nebari and needs some assistance. I wonder if part of the problem is that its planted in a bonsai pot. Do you think planting it in a box so I can get it deeper would make a difference? What do you think? I’ve got 6 JM seedlings and I’m ready to start grafting!!
Fwiw, you want vigorous growth with both the donor and receiving tree, so I'd advise a grow box for a few years while you sort out the root issues.
 
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