Any reason to leave a deciduous airlayer overwinter?

I meant to ask @ryan in the last Q&A but I missed. I figured I’ll see what and if there is a consensus in the forum and then potentially ask in the next Q&A I can participate…

Is there any point on leaving a deciduous airlayer any longer than post leaf drop in the fall? My reasoning is that If a deciduous airlayer was successful, any new leafs next spring will come from the resources stored in the new roots and I guess there will be a balance with the amount of leafs produced that will be somewhat proportional to the amount of root mass so that additional water from the main tree is not really necessary. In other words, there is nothing else contributing to the creation of new roots after the leaves drop in the fall, If there are roots and a cambium “bridge” didn’t form across then the main tree cannot offer anything more than water, and that is no longer needed. Does it make sense? am I wrong?

The cambium transports sugars and starches down from the foliage to the roots, the xylem, the wood, transports water and nutrients as well as stored sugars and starches upward to the foliage. The formation of a cambium bridge doesn’t mean anything except your air layer failed. Leaving the air layer on over winter means that, as long as the host tree’s roots are still alive, they will provide continued support to the air layer in progress in the spring.

As far as I know, the xylem transports water and nutrients dissolved within it, not sugars stored in the roots.

Hi Mike,
My understanding is that xylem transports water and nutrients up, then becomes heart wood, phloem transports sugars and starches down, then becomes bark. Between the to is the cambium, which both grow from?
Rafi, I usually try to remove air layers as soon as they have enough root to survive, as (i believe) they will grow away faster. However, i took an air layer off an elm last year quite late, and nearly lost the the lower remaining tree (although it could have been unrelated). Just trying to think of a horticultural reason to leave it on.

If you can protect your new tree, especially the roots from frost, and keep the roots moist you should be ok.
The sort of theory there’s that the new tree is still used to or reliant on the parent tree. Removing the tree after the leaves drop leaving them to rely on their own juvenile roots can be risky because they don’t have foliage to generate more roots and nurse itself from the shock.
I wrap the airlayer with bubble wrap or insulation (the silver one with bubble wrap in it) over the winter and cut it off prior to bud push, around Feb to March here in Western WA.
You can remove the tree during early fall if you have roots around the ring already, keep it in a greenhouse and place it on a heat mat.

My bad @rafi for whatever reason I thought that the xylem would be responsible for sending stored starches up the tree when a tree comes out of dormancy, but after doing some plant biology research, I see that this is wrong. The phloem can transport sugars either down or up the tree. Glad I know that now…

dear rafi,
how do you know that an airlayer was succesfully? visible signs of roots? you remember the stream were the callus build a bridge and only inspecting the roots could disclose this. this coulb be done Mores safetly in spring.
an other aspect is the stability of the tree with new roots, if wind or other factors impare the physical stability the root could be impared, too
if all is not an issue, separating in autum is fine

@Balatus, my rationale is that no matter what, as soon as leafs fall, I can tease away substrate to see if there are enough roots and if it bridged. There are 4 possibilities:

  1. Enough roots/no bridge: Remove airlayer, plant tree to be able to protect during winter and in early spring.

  2. Enough roots/bridged: Remove airlayer, plant tree to be able to protect during winter and in early spring.

  3. Not enough roots/bridged: No point on redoing anything now, there’s a possibility to try again next spring. Action: undo airlayer.

  4. Not enough roots/unbridged: Probably a dead. Next spring, any leafs that come out, if any, will be from the locally stored resources. If there’s any spring frost they’ll be gone and it is game over. If no frost, maybe there’s a chance. Action: might as well redo the airlayer and leave it over winter.

Hi @Rafi,
I don’t think there is any advantage to separating the layer in the fall. All the things you mention could be better done in the spring and the layer potted when it’s going to start growing. Ryan has mentioned on a few occasions that whatever roots have formed on the layer will be super hardy for the winter because all the sugars and starches that the tree is sending down to the roots in fall will be in those layered roots. He has consistently recommended waiting until spring to separate layers.

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So I asked @ryan on a Q&A, you can find his answer here at 12:57’