Air layer-how deep to cut?

[sfhellwig]

I am about to try my first air layer. I have read the procedure a hundred times. I thought I was ready until I was doing some final reading and come across accounts of "may not have cut deep enough" and "did I cut too deep". So how deep do I cut? I will be doing this on a Trident, for this specific instance. Every book I have read says remove the bark or cut to wood. This would insinuate removing all cambium. But we need to leave the part that still carries water upward. So if I remove bark and insure that there is no green left, how do I know it's right? I remember there being a bonsai site that showed a low air layer essentially to accomplish a new root base. They said they cut an 1/8 in. deep ring just to make sure they would not have it bridge back. What am I missing here?

 

[misfit11]

You need to remove all the cambium or phloem which transports the sugars down to the roots. This will force the tissue to begin growing new roots at the cut site. The woody stem underneath will still be intact to move water up to the leaves.

 

[sfhellwig]

So the wood actually carries water upward? I guess this would be the part I have been missing. As long as the cambium is removed and the sphagnum is moist that should be the main concerns?

 

[garywood]

When you layer there is a problem if you don't go deep enough. The bridging between the cuts has pathways to repair the injury and on strong trees like Trident they will even bridge deep cuts if not wide enough. There is too much made of not cutting into the "wood" or sapwood. there is some water transport there but the majority is through capillary action between the cuts and medium. This why the medium should never dry out. In Al's thread, I'm not callus, I posted a shot of a Trident layer where knob cutters were used to really cut deep to prevent bridging because I knew this would be a multi year project. here is the post.

February 14th, 2010, 06:54 AM
garywood
Member Join Date: Dec 2008
Posts: 77

I really only wanted to follow the thread along but I might have something that would further our understatding of callus and physiology. This is an airlayer on a trident that was done in spring of 09. The intention is not to get roots the first year but roots the second year or even the third. The first year is for only building callus and you can see in the photo there is a difference.in size between the top and bottom cuts. I use knob cutters and make a deep cut into old wood. Draw your own conclusions if callus transports. Wood
Attached Thumbnails

PS I don't know how to LINK

 

[garywood]

I'll try the easy way

 

[sfhellwig]

So the transfer of water is by the sphagnum, not the "wood". That makes better sense. The damp sphagnum is essentially a temporary bridge so that the layer lives AND serves as an inviting place for the roots that will form. I think I get it now. I should have known that the "wood" had little to do with it. I just did a grafting workshop where we watched bark and three-flap grafting. Both of which are an extreme interruption/joining of heart wood. The success lies in rejoining the cambium. I guess I was missing that the damp moss on an air-layer is doing the "keeping alive" until roots form.

Thank you, garywood for the reference to the thread and the picture. The picture reinforces what I thought and I had actually been looking for that thread. I saw the pictures of top-working a while back and couldn't remember the name of the thread. I will not forget it again.

 

[jasonthurston]

OK, if the transfer of water is from the moist sphagnum, not the heartwood, then why bother air layering? Wouldn't it be easier to just cut the branch off and put the cut end into a container of moist sphagnum?

 

[Lorax7]

So the transfer of water is by the sphagnum, not the "wood".

No. The transfer of water from roots to the leaves occurs via the sapwood, not the sphagnum moss. Removing the cambium disrupts the transport of a hormone called auxin from the leaves downward. It accumulates in the area right above the girdle and this stimulates root production there.

Read this thread.

 

[Gaitano]

In the above picture you can see the light yellow color? That’s how deep you go. To the right was a thin layer that had to get removed. When you get it all off you get down to a shiny hardwood. That’s when you know you’ve gone deep enough.



Water is transported up from the roots through the vascular system in the xylem. During an air layer you remove the cambium and the phloem. The xylem is not disrupted nor is the water flow. The water can still reach all the branches and leaves above and below the cut site. This is where the sugars and starches travel downward to the roots. When we disrupt this flow of the sugars and starches because we removed the flow tubes, this photosynthetic “food” stops at the cut site and creates callous and then roots. The sphagnum keeps the area moist so the area doesn’t dry out and roots can develop.