Why do graft site bulge?

[Nishant]

Hello All,

I was wondering what exactly causes the graft to develop a bulge and if there is any way to prevent it from happening.

Why does the bulge develop?
I think it is because the scion develops the woody part at the base so that its weight can be supported. The wood of a normal branch is connected to the wood of the trunk. A graft is more like the epicormic bud growing and so the burr will develop. That's my thought.

Can the bulge formation be prevented?
(1) By keeping the site wrapped with metal wire like strong material, thus not allowing space for the growth of wood.
(2) Grafting be done on a young stock branch. Say for pine, graft on the branches that have shed the needles just the current year. With a young stock branch, chances of success could be higher as well. If the branch will be young, then the wood of stock and scion will grow almost together and the bulge would be minimal.

Please share your thoughts on this. Also, I have seen lots of talk about grafting pines. Does anyone have a picture of a successful pine graft and how does it look a few years after the graft?

 

[Srt8madness]

Old import JBP rehab project

Here’s an old JBP. It was imported many years ago and passed through a number of hands here in the Houston area. It’s never really been properly maintained, resulting in long leggy branches with no interior growth and some major structural problems with the roots. That said, it has an...

www.bonsainut.com

The search function will help too.

 

[Nishant]

what does your reply mean to me? Its a thread showing grafts in early stages. My concern is about how grafts look in future?

Old import JBP rehab project

Here’s an old JBP. It was imported many years ago and passed through a number of hands here in the Houston area. It’s never really been properly maintained, resulting in long leggy branches with no interior growth and some major structural problems with the roots. That said, it has an...

www.bonsainut.com

The search function will help too.

 

[Srt8madness]

what does your reply mean to me? Its a thread showing grafts in early stages. My concern is about how grafts look in future?

It means there's a picture of a completed graft as asked for. Also, it means look it up. There is a search function you can type your keywords onto.

 

[Eckhoffw]

Easy now.
In my understanding,
The bulge is from the callus formed in the healing process. That simple. The cut tissue calluses over (or attempts to roll over) the cut or grafted material.

 

[Shibui]

The bulge is from the callus formed in the healing process. That simple. The cut tissue calluses over (or attempts to roll over) the cut or grafted material.

Initial small bulges can usually be attributed to callus forming. That will often even out as the trunk thickens but there seems to be more to it in the case of some grafts.
Sometimes the root stock section thickens way faster than the scion on top making a big difference between stock and trunk. Don't think that can be explained as simply callus but I don't know what causes it.

 

[Gr8tfuldad]

I wonder can you wound the tree vertically across the graft to blend the two? I assume this would be done a bit at a time as to not girdle the tree.

 

[Bonsai Nut]

Sometimes the graft union will fail - even on a large, mature tree. It depends on the compatibility of root stock and the scion. I've had large grafted citrus in my garden fail after a period where the union would slowly swell over a number of years.

The closer the scion is (genetically) to the root stock, the less likely the graft is to fail from genetic incompatibility. So, for example, a JM Bloodgood cultivar that is grafted on top of a seedling from a JM Bloodgood is probably less likely to fail than a JM Bloodgood scion that is grafted on top of vine maple root stock. There may also be other reasons for a union to fail - including different growth rates of scion and rootstock, different disease or pest resistance, etc. Google "graft union incompatibility" for some great photos.



As far as pine grafts go, here's one of many examples of graft incompatibility. Kotobuki JBP cultivar grafted on top of generic JBP root stock. The tree looks healthy enough, but I don't know if I will ever get the scion to grow to the point that the graft scar will not be noticeable. Meanwhile I have a number of P. strobus cultivars grafted on P. silvestris where the grafts are already almost indistinguishable - even on relatively small trees.




Going back to the OP's original question, the key to a successful graft is going to be: (1) compatibility of scion and rootstock - genetically and physically, and (2) a well-executed graft with a long angled graft scar that will heal well and also tend to "taper" the graft union so the junction is not as abrupt or visually recognizable.

 

[penumbra]

Sometimes the root stock section thickens way faster than the scion on top making a big difference between stock and trunk. Don't think that can be explained as simply callus but I don't know what causes it.

I see this frequently and have a couple of good examples in my landscape. When the root plant is more vigorous than the scion wood, there will inevitably be a swollen trunk.
Bonsai Nut's above ^^^ example is the reverse.

 

[Wires_Guy_wires]

I wonder can you wound the tree vertically across the graft to blend the two? I assume this would be done a bit at a time as to not girdle the tree.

Yes, but this poses a new set of challenges: which ones tissue will fill the gap, and would it increase the swelling or possibly cause one plant to consider the other as pathogen?
I've seen grafts flip teams and consider the scion as unwanted after years of being happy together. One giant necrotic ring was left on both ends.

I think that's part of the reason why jamming a horizontally cut scion on a horizontally chopped rootstock is done less and less. Cacti are about the only exception I know of.

 

[Shibui]

Despite the pictures of horrible differences in graft scars grafts do not always do this. I'd even say that more are successful than not but, of course, we can't see those so only see the bad examples.

I took some spring pictures this morning and was reminded that I grafted this JM around 30 years ago. All above the 1st branch is grafted.

 

[Nishant]

Hello All, I am planning to perform Approach grating and veneer grafting on my Scots pine. Can I do this now? I know the usually recommended time is late winter or early spring just before the tree breaks out if dormancy and so that the pine would not ooze sap when cut.

It can be very difficult for me to time it. So I was wondering if grafting could be done earlier. Will the callus form if grafting is done earlier?

Thanks for the advise

 

[JeffS73]

My personal experience of scots, white and black pine is that they fail if you go too early. Now is way too early in the UK. Sap must be flowing to make a union in the cambium. That means the rootstock is actively growing, which you will see as the buds swelling or candles extending. I have much higher success May/June when buds are actively extending. I've had success Summer through to September too, but I would avoid a hot period, like the 40c last year.

There was a good video knocking about of a chap doing a demo and saying this, can't find my link to it. He used small zip ties to hold grafts together, I tried this and now prefer it to my graft tape.

 

[Nishant]

My personal experience of scots, white and black pine is that they fail if you go too early. Now is way too early in the UK. Sap must be flowing to make a union in the cambium. That means the rootstock is actively growing, which you will see as the buds swelling or candles extending. I have much higher success May/June when buds are actively extending. I've had success Summer through to September too, but I would avoid a hot period, like the 40c last year.

There was a good video knocking about of a chap doing a demo and saying this, can't find my link to it. He used small zip ties to hold grafts together, I tried this and now prefer it to my graft tape.

Thanks fir the reply.

Ah yes the zip ties are really great. I have used them this year on one of the other tree i grafted in September this year and the zip ties was really quite effective for the job of holding the scion in place. I do wrap with tape to prevent from elements.

Coming back to question on timing, when the bud starts swelling the pine must be full of the thick sap and that would get between scion and stock and hinder the union formation. No?

 

[Paradox]

Hello All, I am planning to perform Approach grating and veneer grafting on my Scots pine. Can I do this now? I know the usually recommended time is late winter or early spring just before the tree breaks out if dormancy and so that the pine would not ooze sap when cut.

It can be very difficult for me to time it. So I was wondering if grafting could be done earlier. Will the callus form if grafting is done earlier?

Thanks for the advise

Watch this video from Ryan Neil about grafting pine