David mentioned in another week that Russian comfrey pulls PA‘s down to the soil around it. Is that true for S.Officinale too? How to differentiate between S.Officinale and s.X uplandicum?

Symphytum uplandicum and S. officinale contain PAs (S. uplandicum has more), they do not pull PAs into he soil, when the leaves die they break down and the PAs which are fairly stable go into the surrounding soil. Other plants growing nearby (plants that do not normally contain any PAs) can then uptake those PAs. This can happen with either species. It also means you do not want to use Comfrey leaves as a green manure.

Comfrey is so often recommended for mulching under fruit trees and I have planted some under some young-ish apple trees. Do you think the PAs can travel up a tree?

Is there anything you can do to reverse the PA uptake? I have some S. uplandicum that is near some motherwort that have been growing together for one season. I want to remove the comfrey, replace the soil in that bed and perhaps replant the motherwort elsewhere. Any recommendations on how to "save" my motherwort? Is it worth it or should I just toss it? It is my first year growing Leonurus - it did not do well near the comfrey, but I did have two plants grow significantly in a bed near marigolds. Hoping for next year. I had always heard about "chop and drop" for comfrey (green manure) and had never considered the PAs. Is there any scenario where chop and drop is good if plants uptake the PAs? I guess this is an echo of the above question in regards to PAs and fruit trees.

Absolutely, the PAs are in the soil and anything growing in that soil can uptake the PA’s. So using it as a green manure is a truly bad idea. By the way , the studies showing this can occur are fairly recent and not widely known in the organic and biodynamic communities.

No, there is nothing you can do in the short term except plant herbs you want to use internally away from Comfrey and other PA containing plants. Over several years the PA’s eventually break down (around 3 years) and if no more are deposited in your soil, the soil would be fine.

Thank you this was very helpful. We dumped the dirt under a pyracantha and a sycamore tree. Any chance we can get a link to the article/study. I have some friends in the biodynamic community that need to hear this loud and clear.

If you have them available, I'd like to have a citation or two about the PA uptake. Was talking with an herbalist friend who also owns a native plant nursery and we both wanted to read more about it since we both have comfrey growing under fruit trees. A google search only showed me a study on uptake by animals. Thanks, Lindy

Transfer of pyrrolizidine alkaloids between living plants: A disregarded source of contaminations. Selmar D, Wittke C, Beck-von Wolffersdorff I, Klier B, Lewerenz L, Kleinwächter M, Nowak M. Environ Pollut. 2019 May;248:456-461. doi: 10.1016/j.envpol.2019.02.026. Epub 2019 Feb 15. Interspecific transfer of pyrrolizidine alkaloids: An unconsidered source of contaminations of phytopharmaceuticals and plant derived commodities. Nowak M, Wittke C, Lederer I, Klier B, Kleinwächter M, Selmar D. Food Chem. 2016 Dec 15;213:163-168. doi: 10.1016/j.foodchem.2016.06.069. Epub 2016 Jun 22. Phytomedicine . 2017 Oct 15;34:21-25. doi: 10.1016/j.phymed.2017.07.007. Epub 2017 Jul 11. Horizontal natural product transfer: A potential source of alkaloidal contaminants in phytopharmaceuticals Mahdi Yahyazadeh 1, Melanie Nowak 2, Heiko Kima 2, Dirk Selmar

Thanks for the citations!