Avoiding pot effects

[christophe-rd]

Yesterday April 6th, 2024, I finished repotting Acne and Bepa for which their roots both seem to be limited by the pot size (1-gallon).

Here's a quick thought that I would like to share: Since we are only at the beginning of the growing season, it's fair to assume that plants should not invest too much in their root systems. Therefore, the root system taking the shape of the pot probably comes from last year's growth (see attached pictures). Please feel free to share some readings. From what I read so far, root phenology seems to be poorly understood.

Acne and Bepa are now in 2-gal pots. @lizzieinvancouver, @DeirdreLoughnan, @wangxm-forest, @ngoj1, @FrederikBaumgarten, would you guys agree that we perhaps avoided a meaningful pot effect? Is there a way we could argue this or will it remain a mystery?

[ngoj1]

Hi Christophe,

This is unfortunately not the answer you are probably looking for, but I'm not too sold on the assumption that root systems don't expand much during the beginning of the growing season. I'm by no means an experienced gardener but it's common practice to repot plants in early spring before budburst or after they enter dormancy during the autumn for 2 reasons; 1) you avoid damaging the plant while it is actively growing both shoots and roots because the plant is dormant, and 2) you are performing your repotting before roots initiate growth. This webpage from the Royal Horticultural Society talks in some more detail.

Secondly, this journal article on red maple and sugar maple indicates that root growth initiated a month before budburst, then declined, then resumed again during shoot elongation. There's also this journal article that summarizes optimal transplant studies that discusses that the preference for spring/autumn transplanting differs between species. The staff at UBC Botanical Garden are still complaining about anything to do with Acer taxonomy so I'm hesitant to offer a "revised" phylogeny to assess how applicable this paper is to A. negundo, though this paper briefly touches on its apparent intra-annual variability.

Some quick skimming of other papers failed to give results on transplant optimization for B. papyrifera, but there's one on B. pendula that talks about how the after-effects of transplanting can be mitigated by adequate watering. I'm not sure how applicable this kind of finding would be to a different species, but here's a Betula phylogeny in case you're curious. Both are in subgenus Betula and also section Betula if that helps with generalizability of results.

[christophe-rd]

Hi @ngoj1 ! Thanks for your very detailed answer, I appreciate it.

It would have been ideal to repot the plants in autumn or early spring, however, it wasn't possible. Perhaps my point wasn't clear. Rather, I wanted to say that I wonder whether the fact that we've replanted the trees so late will have a significant impact their growth.

This article mostly talks about how smaller pots lead to smaller biomass increments. Therefore, do you think Acne and Bepa decreased their biomass increment because they lack the space to expand their root system? Thanks again for your research and knowledge on the subject! It's very valuable.

[lizzieinvancouver]

@christophe-rd I think we have to be worried about a pot effect from the photos, but there is nothing we can do now beyond make a note of it and remember it when we get to analysing data. I am more worried about pot effects next year as we try to grow the plants a second year to look for lag effects, so let's keep making sure we avoid pot effects going forward.

This is a good thing to document in a github issue, but we should be sure to also have it in the daily log -- and make sure we have the dates of all pot transfers in that log. I could not quickly find the daily log on this repo, can you point me to it? It should what is happening every day as well as any notes going backward about what happened since we ordered the plants to the best of your memory.

And my thanks also @ngoj1 for the thorough answer!

[christophe-rd]

Hi @lizzieinvancouver. Perfect, yes I keep the daily log updated (as you know I'll transfer soon to Latex).

Here are some pictures of the repotting of Pist yesterday:

[lizzieinvancouver]

@christophe-rd Thanks for keeping track of this! It seems good they're all getting repotted (and, it looks so sunny and nice!).