Large JMaple Ground Layer Advice

Lars Grimm

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Hi All,

I've done a number of successful air layers over the last couple years, but never a large ground layer and I am looking for advice. This Japanese Maple is a larger field grown material with a base approximately 5" across. There were a number of very large scars from sacrifice branches and so I decided to ground layer it this Spring after the leaves hardened. After doing the routine cambial cuts, I used a medium sized plastic put for the new container. I filled it with Boon's mix but packed sphagnum moss directly around the cut site and dressed the surface with sphagnum. In the last couple weeks I've noticed the sphagnum on top is drying out fast and discovered that small feeder roots have started to grow into it. I can't tell if the roots are circumferential but I have indirect evidence of substantial root growth.

How should I approach the next steps given the large size? For smaller air layers that have sufficiently rooted, I will separate them at any time and just provide good aftercare. For such a large specimen though I was considering waiting until late summer/early fall when we get cooler temperatures and then doing the separation.

My separation plan was to just use a saw to cut below the pot and then do my best to stabilize the tree so it doesn't fall over. I'll probably set the plastic pot and secure it in a wooden box. Next Spring I would probably open the pot up to tease out the roots and screw it onto a board to allow horizontal root growth.

Any advice from more experienced folks would be greatly appreciated.

Original picture from a few years ago showing the large sacrifice branches. I ground layered just above the large branch seen on the right.
IMG_2345.JPG

Two pictures from today.
IMG_5467.jpg

IMG_5468.jpg
 

sorce

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This is where I'd use a wire pull saw right under the pot.

Sorce
 

Dav4

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I would hold off on separating the layer until mid September at the earliest... remember how hot last September and early October was last year? Fwiw, there's no harm waiting to do the deed next year at the typical re-potting time for maples in your local. Also, I've learned the hard way that being too aggressive manipulating newly formed roots on a layer- read that as less then a year of age- can lead to collapse of the layer, at least in semi-dwarf varieties. Great trunk on this one!
 

Bonsai Nut

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Think about it from a botanical perspective. You want those roots to be established before winter... or else not separate before next year spring.

In order for the roots to get established you need a healthy mass of foliage to provide enough energy/carbs. However as @Dav4 pointed out, you are in a Catch22 situation - you need the foliage, but the roots won't be able to provide a ton of water (yet) so the tree will be at risk of desiccation. I would only separate the layer now if you can protect it from wind and intense sun - like a minigreenhouse or a humidity tent.

Be careful with maples when you separate the layer. Make sure you use a waterproof cut paste to avoid fungus getting into the trunk. Also consider using fungicide prophylactically.
 

Paulpash

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I'd allow a little more time for the roots to partially lignify (second year air layer roots can still be manipulated). This will allow you to tie them up out of the way without breaking any delicate roots while you use a sharp saw on it. The Silky one @markyscott recommended which I bought makes short work of jobs like these. I've done a few of these separations and they are fiddly and a bit daunting, especially if you do it too fast and the roots aren't particularly robust.

The roots produced by an air layer are packed with sugars as all of the tree's carbs for that growing season have been dumped at the cut point and the new root system. They will undergo the same hardening off period as did the old root system. I have kept layers on during winter before albeit in the UK with Winters rarely going lower than - 5C.
 
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sorce

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Amen. You might even go as far as "Repotting" the layer.

I'd build a larger box in 2 parts like so..

Capture+_2020-08-01-06-54-17.png

Wider than the old box so when you clamp it around the tree, the old box supports it. Then you have saw space between the top box and the old soil line.

And leave it all the way till when the hell ever.

Sorce
 

Lars Grimm

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Think about it from a botanical perspective. You want those roots to be established before winter... or else not separate before next year spring.

In order for the roots to get established you need a healthy mass of foliage to provide enough energy/carbs. However as @Dav4 pointed out, you are in a Catch22 situation - you need the foliage, but the roots won't be able to provide a ton of water (yet) so the tree will be at risk of desiccation. I would only separate the layer now if you can protect it from wind and intense sun - like a minigreenhouse or a humidity tent.

Currently there is a pretty healthy mass of foliage, which I image draws a lot of water. Humidity is not a problem as our normal humidity is pretty high (91% this am). It is the heat that I worry about with temperatures routinely in the 90s. I do have it under a pergola plus 30% shade cloth. Next spring is the other option I am considering that I forgot to mention.

Be careful with maples when you separate the layer. Make sure you use a waterproof cut paste to avoid fungus getting into the trunk. Also consider using fungicide prophylactically.

I'm definitely very proactive around antifungals (systemic granules and topical sprays) here as they are a recurrent problem. Botanically, can fungus enter the tree through the woody structural tissue where I make my separation cut? I always assumed it traverses through the vascular tissues.
 

Lars Grimm

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Amen. You might even go as far as "Repotting" the layer.

I'd build a larger box in 2 parts like so..

View attachment 319998

Wider than the old box so when you clamp it around the tree, the old box supports it. Then you have saw space between the top box and the old soil line.

And leave it all the way till when the hell ever.

Sorce
Now that is definitely thinking outside the box....
 

sorce

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Now that is definitely thinking outside the box....

I was thinking the other day, if you ever find me Inside the box...
Shoot me!

Does that make sense? I think if you fluff up and out your roots, you can slide this contraption under safely, IMO, basket edges on a layer or whatever, to air root prune, greatly increases the capability of the space available.

Sorce
 

Lars Grimm

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I was thinking the other day, if you ever find me Inside the box...
Shoot me!

Does that make sense? I think if you fluff up and out your roots, you can slide this contraption under safely, IMO, basket edges on a layer or whatever, to air root prune, greatly increases the capability of the space available.

Sorce

It does make sense, although my goal is to be able to screw this onto a board in the near future. I might just go for a slip pot approach which would essentially do what you suggest but allow for even more root growth and then do a formal repot in the spring.
 

sorce

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slip pot approach

The entire thing?
I would just want to see the outward root Growth of the new roots farther than the circle green pot allows. Anything to accomplish that with the least disruption of bother root systems.

If there is an airspace between, that wouldn't suck, cuz I don't think I'd want to Chuck the base.🧐

Sorce
 

Lars Grimm

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The entire thing?
I would just want to see the outward root Growth of the new roots farther than the circle green pot allows. Anything to accomplish that with the least disruption of bother root systems.

If there is an airspace between, that wouldn't suck, cuz I don't think I'd want to Chuck the base.🧐

Sorce

I was thinking I could just get a larger pot than the green one, carefully remove the green one and slide the new one around, then fill the sides with new soil. The current box is actually much wider than the one in the picture I uploaded.
 
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