marcotting vs rooting question

[brian]

I had never attempted air-layering / marcotting before, but I have done cleft grafting and rooting many times.  I was reading about marcotting and watching some videos and it seems odd to me that the leaves on the selected branch are left on.  I always remove all or nearly all leaves when rooting of grafting to keep them from drying out. 

After the bark (w/ phloem) is removed, isn't marcotting functionally the same as rooting?  Or is the wood (xylem) still transporting water into the branch and is this the reason marcotting is superior to cutting the limb off entirely and rooting it? 

I just attempted this on my ice cream bean tree and I must admit I feel like the girdled branch is going to just wilt completely by tomorrow because these things are so thirsty.  I can't imagine it is uptaking any significant amount of moisture from the peat bag/wrapping.

Sorry if this seems like such a basic question but I found a million guides on grafting but none went into any detail about *why* it is done this way.

[Rauf]

It's interesting for me too. It seems wood still is transporting  the water.

[Galatians522]

The girdling does several things as I understand it. For one thing, girdling stresses the branch and helps to induce changes in plant hormones that contribute to the formation of root primordia. As you mentioned, the xylem is still bringing water to the leaves. This keeps the branch hydrated. However, with the cambium gone the sugars from the leaves are not able to get down to the roots. Those extra sugars provide energy for the branch to make roots. More leaves means more sugars and better rooting. As a result, you actually want maximum leaf levels and sun exposure. Do not remove any leaves or shade the air layer. In my experience, most things that propagate from cuttings will also air layer, but I believe there are exceptions to this.

[elouicious]

The girdling does several things as I understand it. For one thing, girdling stresses the branch and helps to induce changes in plant hormones that contribute to the formation of root primordia. As you mentioned, the xylem is still bringing water to the leaves. This keeps the branch hydrated. However, with the cambium gone the sugars from the leaves are not able to get down to the roots. Those extra sugars provide energy for the branch to make roots. More leaves means more sugars and better rooting. As a result, you actually want maximum leaf levels and sun exposure. Do not remove any leaves or shade the air layer. In my experience, most things that propagate from cuttings will also air layer, but I believe there are exceptions to this.

excellent answer

[Finca La Isla]

That is a very good answer except for the last point. Any cutting that can be rooted can be air layered. But not necessarily the other way around.
We commercially layer rambutan, for example. We must get 90% or better. We’d never get that with cuttings if any at all.
Peter

[Galatians522]

That is a very good answer except for the last point. Any cutting that can be rooted can be air layered. But not necessarily the other way around.
We commercially layer rambutan, for example. We must get 90% or better. We’d never get that with cuttings if any at all.
Peter

I say that because of Macadamia. I have air layered lychee on a commercial level. When we tried macadamia on a small scale we got callus formation but no roots until we cut them off and treated them like cuttings. Was it a fluke??? I don't know. Also, Atemoya can be rooted from cuttings according to Australian literature. I have never gotten it to air layer successfully because it has weak wood and the layers have always gotten snapped off by wind. In theory it works, but in practice its not practical. That is why I add the caveat.

[Finca La Isla]

That’s interesting. Rooting cuttings and marcotting have a lot in common. Since the whole thing is alive and supported by a root system it makes sense that marcotting should be more forgiving. But I guess, then in agriculture, there’s always an exception.
Thanks, Peter

[brian]

Thank you for the responses.  When I did the marcott on my inga I wasn't thinking about the stripped wood still being alive and useful, so I wasn't paying attention to how well the peat bag was covering it, only focusing on the child side of the girdled patch.  I am now thinking it is imperative that the whole stripped wood area is covered by the peat bag to keep it from drying out and cutting off the flow of water up from the parent tree to the child.  I went to check on my work and it looks like I do have the wood completely covered, and the branch has not wilted. 

this is what I was worried about:


I also found an article segment specifically about air-layer versus cuttings for Inga.  It says 100% success with airlayer, 55% success with cuttings *that still have all their leaves*, and 0% success with cuttings that had their leaves removed.  Very interesting.  Also, it mentions rooting hormone is beneficial here, something I had also included in my effort.


New Forests1   5:37–51, 1998
Vegetative propagation of Inga feuillei from shootcuttings and air layering
...
Compound leaves were either reduced in area or removed entirely before auxin pretreatmentwith 0, 0.3, or 0.8% indolebutyric acid (IBA) followed by sticking under mist or in a poly-ethylene enclosure.
Leafless cuttings did not root regardless of moisture management system  or auxin pretreatment, whereas 55% rooting of leafy cuttings was observed.
Leafy cuttings rooted significantly better under mist than in a polyethylene enclosure.
Auxin treatment at thehigher level increased rooting percentage approximately two fold for larger diameter cuttings(8.1 to 20 mm), but  had no effect on the smaller  cuttings  (2 to 8 mm), and resulted in anapproximately three fold increase in the number of roots/rooted cutting for both stem diameterclasses.
Auxin treatment did not affect rooting percentage of leafy softwood cuttings underfog, however it did increase the number of roots per rooted cutting.
One hundred percent of airlayered shoots rooted within 5 weeks with or without auxin pretreatment, and all rooted layerssurvived transplanting to soil.
Possible implications of this research on agroforestry, selection,genetic improvement, and conservation are discussed.

[drymifolia]

It says 100% success with airlayer, 55% success with cuttings *that still have all their leaves*, and 0% success with cuttings that had their leaves removed

That's similar to Mexican avocados, which root at pretty high rates (for the patient) but only when leaves are left intact. You need to root them under intermittent mist or humidity domes, because it takes many months to root and they will dry out otherwise.

The theory put forth in the old research papers about avocado rooting was that root formation is triggered by a buildup of carbohydrates in the lower stem, which can only occur when you have ongoing photosynthesis in the cutting. I'm guessing it's similar for other species that only root easily with leaves left on.

[brian]

It has been nearly two months since I started the airlayer on my inga.  The branch is still very healthy but I have yet to see roots appear on the soil bag.  The article I posted mentioned 100% success with rooting after five weeks.  Should I cut the branch and assume it has roots they just haven't reached the edge of the bag yet to become visible?

I would just wait until they appear but colder weather (~38F) is coming and I have to haul most of my trees back into the greenhouse.  The inga is too big to move now that I up-potted it into a 35gal container knowing that it will be trashed when winter comes.  I am guessing that near freezing weather could harm the airlayer, but I might be worrying about nothing.  I expect the parent tree will be fine.

Should I cut the airlayer now and put it in the heated greenhouse?  Or leave it as-is until it shows roots?

[brian]

oh, I guess I got my answer, the roots just appeared today!  I am going to cut it off

[Seanny]

Wait for more roots

[NateTheGreat]

That is a very good answer except for the last point. Any cutting that can be rooted can be air layered. But not necessarily the other way around.
We commercially layer rambutan, for example. We must get 90% or better. We’d never get that with cuttings if any at all.
Peter

I say that because of Macadamia. I have air layered lychee on a commercial level. When we tried macadamia on a small scale we got callus formation but no roots until we cut them off and treated them like cuttings. Was it a fluke??? I don't know. Also, Atemoya can be rooted from cuttings according to Australian literature. I have never gotten it to air layer successfully because it has weak wood and the layers have always gotten snapped off by wind. In theory it works, but in practice its not practical. That is why I add the caveat.

https://tropicalfruitforum.com/index.php?topic=47077.0 Macadamia can be air layered

[Finca La Isla]

So we wrap layers in foil and it’s easy to unroll a bit to check the progress. If weather were no consideration I would want to see the medium full of roots. What I can’t see from the photo is how many roots there actually are. In any case the layer is successful so, congratulations. When to cut it is something to figure out but at least you know it works for you. After you cut the layer away you might then cut foliage back depending on how much rooting is present. Seek a balance.
Peter

[ScottR]

Nice job Brian, now to keep it alive in transition from layer to potted plant best o f luck