Yamadori collection timing

Hi everybody! Would be greatful for a clearification on best timing for collecting yamadori, in particular decidious.

When buds push or swells in spring seems to be the common best advice for collecting decidious material. Would it not be better to have the first growth harden off before collecting? Then you are in energy positive and the new foliage mass will help rebuild the roots post collection.

At bud push the tree still uses its built up energy to grow, so in my mind this is a bad time for tampering with the roots and stress the tree. Same reasoning goes for timing of repotting.
What am I missing here?

Thanks in advance!

I believe you have the pre bud push and autumn approaches. In between my take is, that yes, while energy positive you severely limit the available resources from cutting down the root system. So photosynthetic maas above can not sustain without the roots below.

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As @antelion said, there won’t be enough root mass to support that much foliage. That’s assuming you’re collecting a sizable piece of material and a relatively small root ball. I’ve “collected” small red maple from around my yard all year, but they’re basically sprouts. I was able to get almost all of their roots. I’ve also collected tiny elms and they super hated it. :cry:

It is also species specific. Some have found that collecting oak in the fall works better for that species. Where you live matters as well. There’s a Carolina Willow that I want to collect. I could probably do it now as there really isn’t that much of a winter here, but I’m still going to wait until late winter/early spring. It’s not like it’s going anywhere. :laughing:

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Thank you very much you guys! This makes sense. With this in mind, would it also make sense to reduce foliage mass in the case of collecting after hardening of the first flush?

@Geir_Norway you might try reading Zach Smith’s at Bonsai South blog. He collects many deciduous trees and talks about different timing based on species. I reached out to him for some advice American Hornbeam. He is really helpful and doesn’t mind giving advice. Best of luck on your collecting, I have a number of American hornbeam and beech tag on my property to collect this year.

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I would stick to collecting in spring or fall, not post-flush. Here’s my reasoning:

At bud break the tree is in an energy positive, if you collect it at that time it can regulate the amount of foliage produced to what the roots (that you’ve collected) can handle. Also temperatures are lower which lessens the amount of water needed for cooling (which is >95% of all water uptake). And it gives the tree more time to grow new roots before the growing season is over (from you nickname I take it that your from Norway which means you have a short growing season to start with so maximizing the amount of time for root growth is even more important). An added bonus is that you only mess with one part of the tree, the roots and you don’t have to touch the foliage.

If, on the other hand, you collect during the summer after the first flush has hardened you shock the tree more. The tree has already put out the amount of foliage that can be supported by the whole root mass and now all of a sudden a lot of it is cut off. On top of that it might be hot and the tree would need a lot of water for cooling and only has a compromised small root system to do that. If you reduce the foliage to reduce the water demand you’ve now disturbed not only the roots but the foliage as well.

Early fall is another good time to collect, especially some species, like spruce, as they experience rapid root growth during the vascular growth season (which is the latter part of the summer and fall). If you collect after the risk of heat spells the tree again needs less water for cooling and can concentrate all the energy it has accumulated during the summer to grow new roots before winter hits. This might result in less buds and a weaker push the following spring but that’s just the tree regulating its growth to what the root system can support.

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Interesting that your elms have hated collection “off season”, what species of elm do you have? Because I’ve had the opposite experience. For two years I have just cruelly yanked out any elm seedlings (Ulmus glabra) I find in my yard without even trying to get all the roots out and I’m still waiting for my first elm seedling to die. They seem to not even notice being planted in a pot, they just keep on growing like nothing’s happened.

Thank you for your extensive explanation. It is highly appreciated and it was really helpful and clarified a lot for me! However there is one thing from your reply I hope you can help me clarify a bit more.

In my understanding the switch from energy negative to energy positive occurs when the new growth has hardened off, as that’s the point the tree can start photosynthesis and reaccumulate energy. Up to that point I thought the tree uses its stored energy to create and push new growth all the way up to hardening.

It’s just a minor nuance but you mentioned that its in energy positive when the buds break. And it also makes sense that the new growth are able to photosynthesise as soon as it is exposed to sunlight. Is that a correct interpretation in your mind?

The tree is in an energy positive before the buds break as it has all the stored energy from last year for the spring growth push stored in its trunk and roots. Once the buds start to break the tree dumps all the stored energy to the new growth and at the beginning the new leaves take more energy than they produce, thus putting the tree in an energy negative. Once the new growth hardens it transpires less and starts producing more than it takes and the tree is again in an energy positive.

You’re correct that the leaves start photosynthesizing as soon as they emerge but as they’re still small the surface area is small and energy production is lower. Only once the leaves reach their full size they photosynthesize at full capacity.

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I think in this case it’s important to differentiate between energy state and water transport. If you dig in summer and reduce the root system, the tree will likely not be able to transport enough water to foliage to survive the higher heat. Remember, cooling is part of the equation as well as photosynthesis. If the tree can’t keep itself cool, it will start to sheds foliage to reduce it’s water needs. This can be a downward spiral for an already weakened plant.

I think there may be a few caveats to this such as oaks during summer dormancy, but they have a thicker cuticle on the leaf to reduce transpiration.

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