Air layering vs cutting. Technically, what's the difference?

[HarleyD]

Hey Everyone,

First time poster here.

I'm currently trying to propagate some particular varieties of Japanese Maple (Hana Matoi, Goshiki Shidare) and I've heard that you can air-layer these, but cuttings don't root so well.

I'm pretty new to this so this might be a dumb question. The way I see it, air layering and cutting are essentially the same thing (assuming you use the ring-bark method of air-layering) that is, you're cutting off the flow of nutrients to the branch of a plant and in order to survive the branch now has to produce roots at the break. My question is, why does one method work while the other doesn't? What are the advantages of one method over the other?

Thanks in advance,
~Harley

[greg27]

Air layering involves cutting through the layer of the branch that transports the sugars/energy that the leaves generate through photosynthesis to the rest of the plant (phloem), but not the layer that transports water/nutrients from the roots to the leaves (xylem). So the part of the plant above the layer site is still fed by the roots. The energy generated by the leaves stops at the layer site and that's why you get roots forming.

This page has a good explanation, which I came across when looking up the names of the different layers: https://www.evergreengardenworks.com/airlayer.htm

[Bougy Fan]

Hi Harley and welcome. The simple answer is when you do an air layer it is still attached to the tree. When you do a cutting you cut it off the tree. Generally air layers will succeed while cuttings can dry out if not kept humid. Air layers are slower but you can do larger size material too.

[HarleyD]

Thanks a lot for the info.

I was under the impression that nutrients flowed both ways, up and down through the cambium and that the wood underneath was essentially structural only.

I've learnt something new today!

cheers,
-Harley

[dansai]

Hi Hayley and welcome to Ausbonsai

A little more info on the Xylem, Phloem and Cambium for you. The cambium is the green area that is can be seen when scratching the bark of thin barked trees or young shoots. This is where new cells are created. On the inside new xylem cells are created which become the wood of woody trees. The newer wood does the transport of water and nutrients from the roots to the leaves (also known as sapwood), and then as it ages it stops transporting water and lignifies to become stronger and becomes structural (heartwood).

On the outside of the cambium the new phloem cells are created which transport sugars and other nutrients downwards to support the growth of new cells and roots. As these age they become the bark of the tree and how they age and how the species deals with the older cells determines what the bark of the tree looks like.

So when you do an air layer you need to make sure you move the bark, phloem and cambium. If you leave any cambium the bark will regenerate and you won't get roots. You can safely go a little further than the cambium but you don't want to go too far into the xylem or you will reduce the ability of the tree to get water to the higher areas of the tree and you could kill the part above the layer.

Some trees strike easily from cuttings but don't necessarily air layer well. Some trees won't strike cuttings easily, or at all, but layer easily. Some do both and some are hard to get roots by either method. Japanese maples tend to fall into the category of not striking so well from cuttings but will layer quite easily. Some forms of Japanese maple don't grow well on their own roots and are grafted. These may air layer easily but may not do well after removal from the parent tree.

[austindrake]

Some forms of Japanese maple don't grow well on their own roots and are grafted. These may air layer easily but may not do well after removal from the parent tree.

This is something I've always struggled with conceptually - when a particular cultivar is discovered, surely it was grown from seed to an age where it's characteristics were able to be identified, and therefore survives well on it's own roots... So why do air-layers of these cultivars seem to struggle on their own roots? Or is it simply 'struggle' by comparison to a vigorous rootstock?

[shibui]

Some of my seedling JM struggle to stay alive because they have weak roots. I graft those at the earliest opportunity (4-5 months old) to keep them alive so I can assess the quality of that particular individual.
I believe there are also individuals in all plant species that are better able (genetic differences) to grow roots as cuttings. When we gather wild (natives) material for cuttings success rates are often quite low (partly due to plant health but also genetic differences) The ones that have a predisposition to rooting are the ones that grow. Cuttings taken from those have much better success rates - partly because thse plants are healthier but I believe also partly genetic.

It is likely that some JM varieties are also resistant to rooting as cuttings but that does not usually matter as most are grafted to propagate.

[TimS]

I experienced this while attempting to germinate the seed of weeping japanese maples. There is a thread here somewhere about it, but basically i put in 1200+ seeds, i think 400-500 germinated, and of all those i have a grand total of 1 that has survived on its own roots into year 2 and i have given it to my mum to enjoy for however many years it manages to survive before it inevitably carks it too!