Air layer oak aftercare help?

Hi there!

I live in Los Angeles.

I air-layered a cork oak. Layered March 2017, checked for good roots in Oct and again in January.

Finally split March 1, 2018 with some good roots in a small-fist-sized ball of sphagnum.

I planted the top in a new pot with well draining but not super-airy bonsai soil. I did not trim anything from the top.

After 3 weeks it is March 22nd, and the leaves are going yellow. It has been rainy most of March and the pot has never dried out fully.

And so, my questions:

  1. Is it normal for the tree to drop all its leaves during this time? So, nothing to worry about?
  2. Should I have cut back the top leaves to reduce transpiration (but as I said, it has been humid and rainy).
    2a. Should I cut the top back now?
  3. Should I have potted it in something with more oxygen, more porous and root-stimulating, like pumice?
    3a. Should I take it out and do that now?
    3b. The reason I ask is that maybe it has been too moist and the roots are rotting?

Thanks in advance for any advice! See attached pics of the top (yellowed leaves) and the bottom (leaves look good).



I’m no expert on oaks at all, but it seems like you have a pretty good theory already. Since it’s been so wet, with few roots, I think you should really hold back on watering and see if that helps. Also did you tease open the sphagnum and rootball a bit before potting?

I would not take it out an repot it, disturbing the roots again right now could be detrimental. Just keep it quite dry for a bit and see if that helps stabilize it.

For me that looks like that much leafs do not get enough water!
In the pics it loos like only the inner leaves get yellow.
Plants usually do that to protect the growing tips.
Mauro Stemberger toled me they put transparent plastic bags over new collected oaks with not that much roots to protect them from transpiration.

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Sure, but maintaining humidity around the tree in a bag isn’t the same as overwatering a not very aerated soil. I think the aeration in the soil or lack thereof may be a key factor in this specific case that changes how we approach this Oak. I am familiar with this plastic bag method, it’s similar to a horticultural process called “sweating” that I’ve used on many collected deciduous trees. I’m not totally convinced it will help at this point given that the tree is already in full leaf and this issue may lie in the soil :thinking:.

You’ve said nothing about feeding. I’d use some Miracle-Gro Quick Start transplanting solution.

I just checked out iron deficiencies, but that’s where the veins are green and the the gaps are yellow. Yours are the opposite.

For yellow veins and green in the gaps along with those brown spots, it could be a potassium deficiency. Miracle Gro Quick Start has an NPK of 4-12-4 which is good for roots, but you’ll want to add some potash to get the potassium (K, in NPK) a little higher.

Good luck!

Hmmm, the thing that would be number one on my list of things NOT to do to this tree is fertilize it in any way shape or form.

It’s been separated from it’s parent tree for only 3 weeks, it most definitely does not have any nutrient deficiencies yet, and fertilizing a tree in distress is a great way to kill it faster.

Like Ryan always says, restablish a balance of water an oxygen, see how it responds and then take it from there. If you think an emergency repot really is in order, do it in a way that you basically don’t touch the roots at all, don’t try to poke all the old soil out. But again I would reccomend letting it dry out a bit before even trying that.


Thanks everyone for chiming in! I talked to an oak guy, a couple local experts and Ted Matson (curator at the Huntington Gardens collection), and the consensus seems to be pretty much exactly the advice of “Mike_Hennigan”:

Yes, I should have tried to gently remove some of the sphagnum to open up the ball to the air and potted it in airier soil. But that’s water under the bridge. Now leave it alone, don’t water it too much, and see what happens. So that’s what I’ll do. Thanks so much for all the responses!

I’ll try to remember to report back…

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I agree, not to fertilize yet.

Update! As you can read above, the top of my air layer was on the high speed train to Deadtown, USA, but…

In March, a single oxalis weed grew with 4 leaves–a lucky sign? I figured, what the heck, let’s try one more thing…

Ryan’s broken-record “balance of water and oxygen” kept ringing in my brain, and I had learned on the streams that pumice is the best for root generation and you should not overpot. So…

I potted it into a small container with 100% pumice. When I took it out to repot, there were no roots–none, zero–just a heck of a lot of callous. Perhaps we hadn’t seen roots when we thought we did earlier.

Then I just left it alone.

Low and behold… June 3rd, more than 2 months later–a bud sprouted! A miracle!

By June 18th I had a full branch of buds. Now it’s July 6th and still only two branches have a few leaves, and the rest of the tree still seems very dead. But we’ll just keep waiting!

Never give up! Balance of water and oxygen! Nature finds a way!



When I see a person with its head under water, I would not spent much time discussing sport or healthy food. Bring him out of water!
Shelter your tree from any additional rain and water it only if the soil dry out, do this 50 times and your tree will be recovered.

Hello Keegan,
What you are seeing is typical with oaks in my experience in Northern California here. After digging out of the ground or a major repotting it is normal for all the leaves to drop. I have even had trees that dry out for a few days suddenly drop all their leaves only to regrow within a few weeks, much like a defoliation. It seems to be a reaction to stress and a preservation reaction.

As Ryan suggests the strength of these trees seems to be in their vascular system, trunk, branches and roots. I would recommend not cutting off leaves when this happens as some of the nutrients in the leaves may be reabsorbed into the trunk much like winter dormancy. With time and continued good conditions (balance of water and oxygen) these things want to live.

Your repot into pumice was a good plan also. Straight pumice seems to have the best balance to begin root growth. Never give up on an oak! 4 to 6 months are sometimes needed to get a big resurrection on these trees. Watch the small buds closely. If they remain solid and don’t shrink or dry out you have a chance they will come back strong.

Good Luck with this one.