While we don't yet have complete data on the impacts of one invasive species on another (in this case, Garlic Mustard with Lesser Celandine), some are known to alter habitat in ways that make it more or less suitable for their colonization. (Whether they help or hinder themselves depends on the species. Recent research suggests Garlic Mustard, for instance, actually hinders its own persistence over time.) Overall, it's a complex issue, involving factors outside of plant-on-plant competition. Earthworm activity, soil microbes, allelochemicals (compounds produced by one plant to hamper the growth of another), and other changes in soil characteristics all impact how likely any given plant is to survive and thrive, native or otherwise. Climate change is also unfortunately adding another layer of complexity and unpredictability to the issue.
https://extension.umd.edu/resource/why-are-invasive-plants-problem

This phenomenon of self-limitation and other issues surrounding invasive plant control have recently come to light regarding efforts to eradicate them. Research strongly suggests that, with Garlic Mustard at least, actually leaving colonies alone results in much greater self-control of their numbers over time than interventions with removal. Negative side effects of removal efforts include unintentional trampling of soil in the process and therefore further degradation of the habitat one is trying to restore. Here is an interesting article about the Garlic Mustard research, even though the article title is a bit generalized and alarming as a result: https://www.northcountrypublicradio.org/news/story/43550/20210409/do-nothing-about-invasive-plants?fbclid=IwAR0qEtvU_32-cKmeHPQ734UWP_WmXrd_gcNPPxBRo5CZSyzUwsyHDthXGlk

This is not to suggest the same can be said for Lesser Celandine; more study is needed. It is likely that browsing pressure from deer, tied to the Garlic Mustard outbreaks (especially with the intervening damage done by the earthworms they introduce), is hampering Celandine control efforts as well. Deer will consume just about anything - distasteful and even poisonous plants - when starving, so if local herds did browse Garlic Mustard, they may have been under pressure. Rabbit browse is another possibility, and perhaps the plant isn't as objectionable to them. Lesser Celandine goes dormant so quickly that they have limited time to sample them, if they even can stomach their tissues.

The general take-home message so far about invasive plant control is to exclude deer or reduce their impacts whenever feasible and to replant with locally-sourced native species (appropriate to the habitat, of course). Physical removal of the invasives in the meantime may or may not be useful, as was shown in the study.

Miri

On 05/11/2021 12:40 PM Ask Extension <<personal data hidden>> wrote:

 

 

You're welcome.