How can you control liverwort organically?

March 23, 2022 Ask the Expert, Garden Design and Maintenance

Question:

For the first time last summer I identified many liverworts growing in my vegetable garden. I did some research and found out the cause and best practices to prevent them. However, some solutions for eradicating them were chemical. Since all my gardens are organic I would like your best organic solution for eradicating the weed. Since they are in my vegetable garden at quite a high level, some of the solutions I found on-line were acids which will change my pH. I’m wondering if covering the liverworts with a few inches of loam and straw kill them? If that would be a good solution, when the straw decomposes, will the liverworts reestablish?

Answer:

Abi Griffith, Horticulture Community Education Assistant

As you probably already know, liverworts grow vigorously in conditions with high humidity, high nutrient levels (especially nitrogen and phosphorus), and high soil moisture and spread by spores.

Unfortunately they are tricky to manage once you have them, but in general, you want to take away these favorable conditions as much as possible.

I’m including an excerpt from a factsheet about liverwort from Oregon State University, outlining cultural practices to control liverwort in a greenhouse setting (where it seems to be a problem), but principles would be applicable in other settings:

Cultural practices that can assist with discouraging liverwort proliferation include:

• Consider ways to modify your irrigation practices to limit overwatering. Liverworts (and pearlwort) thrive in wet conditions, and any practice that limits the amount of water will decrease liverwort vigor.

• Incorporating or dibbling fertilizers rather than topdressing.

• Increase air flow throughout your crop. Anything that increases airflow and decreases humidity should help reduce liverwort vigor.

Keeping all this in mind, anything you can do to keep things less congested and more dry will help. If you want to mulch, I would consider avoiding straw, which retains water, and consider coarser materials that drain well such as coarse bark, cocoa hulls or even rice hulls. This article explores rice hull use. You could try planting into holes in landscape fabric for longer-season, heat loving vegetables, to control and smother any weeds. Also, if timing allows, cover whole sections of liverwort infested areas of your garden with a weighted tarp to solarize what is there and then follow the cultural controls after. It may be a bit of a process! Curious whether the site you selected for your garden is overly wet/humid as well?

Here is another article for further reference.