Moss and Liverwort, the Garden’s Oldest Frenemies

Cool weather plus rain equals one final flush of late-season growth for our gardens. Primarily of the weed sort, trying to live out their short life spans in time to reproduce the next seven generations of intensive labor if we don’t keep up. Where some visitors more obviously don’t belong, there are also those unintentional additions who live in a sort of grey area, and for me, deciding their fate can be a bit of a conundrum.

The visitors I speak of are mosses and liverwort, which can be seen as an unsightly nuisance, indicating that something is “off ” in the garden ecosystem, or embraced as welcomed guests of the ancient variety equally worthy of cultivation as any other ornamental. With an increase in atmospheric moisture, after a summer hibernation, they bounce back to life, ready to stake claim on more garden space, and as they continue their conquest. And though they have their place, we must carefully consider how much success we want them to achieve.

Mosses and liverworts have a long history dating back to prehistoric times. Fossilized specimens indicate they were among the first plants to colonize land. These bryophytes are nonvascular plants and differ from most other garden plants as they have poor conductive tubing and cannot survive well in places where water is not always available. So, if you have areas of poor drainage and moderate shade in the garden, chances are moss and/or liverwort have made themselves right at home.

Depending on the variety and location, moss can have a soft, almost whimsical presence about it, and in many ways gives the garden an air of maturity. In contrast, the appearance of liverwort in a garden can be upsetting (at least it was to me) if you’re unfamiliar with it.

The name sounds like the poorly wrapped meat of last resort you find at the bottom of your freezer, and in the garden it can look like what you’d find growing inside a well-stocked freezer that’s experienced a few decades of neglect sitting abandoned in a field. The overlapping layers of frog-green thallus (the “leaf ”) form slimy-looking masses that give the impression of having sinister intentions, like growing along shady pathways in hopes you’ll slip and fall so it can eat you.

Even when you realize it’s not an escaped laboratory experiment, it still seems like something that shouldn’t be allowed around your other garden plants. While its occupation of an area indicates poor drainage to some degree, looking at the tight, sometimes crusty, compacted layers, you wonder if water can get through it at all. This can be especially concerning if you find it growing among potted plants, either in your own collection or at greenhouses and nurseries.

Alas, liverwort is in most ways harmless. Water easily penetrates it and, like moss, it can actually be an effective ground cover to help prevent soil erosion. Around mature plants, both potted and in-ground, it poses little threat. However, both moss and liverwort can hinder the growth of seedlings as they will compete for moisture and nutrients.

Personally, I think both moss and liverwort have their own unique charms and can add some depth to a garden. They look great around brick and rockeries, or as some added texture among native vegetation. I can also appreciate them in the nooks and crannies where other plants just can’t seem to thrive. Often in those areas, they foster a mini-ecosystem that brings in a menagerie of peculiar specimens, and it’s fun to watch what makes themselves at home.

On the other hand, the unmitigated growth of moss and liverwort can look chaotic and unsightly, especially in a newly established garden that needs more time for existing plants to mature and the empty spaces to be filled in with fresh nursery finds. Adding plants to a garden that is overrun by liverwort can be a bit of a headache because trying to dig into it is like chipping away at a corkboard.

There are some products out there that are said to help kill both moss and liverwort. I’ve seen iron sulfate and laundry detergent thrown around, but their effect is debatable. The best way to get rid of it is manually, and work to improve the conditions of the site so it’s less appealing for them to want to grow there. Luckily, removal is fairly easy and satisfying since each specimen sits on the surface of the soil and grows to form dense mats, so it’s similar to tearing up chunks of carpet.

While easy to remove, liverwort (as well as moss to a lesser degree) clings to the topsoil with what little root system it has and will be hard-pressed to give any up, which means it’ll take a bit of muscle to manage all the material you’ll be moving around, which makes this project perfect for cooler fall days.

Be sure to have a supply of new soil on hand to replace what is hauled away. I recommend using a combination of topsoil and chunky bark to improve the drainage of the areas most afflicted.

As with most weeds, there’s a good chance moss and liverwort will make their way back into the garden. Should you determine the battle futile, perhaps consider taking their cue and planting some ferns, hosta, foam flower, and epimedium to create a thriving damp and shady shrine. If not for your own sanity, then to honor their contribution to making gardens (and life in general) possible.