A New Look at Mosses
It is that time of year when the garden is done, the birds are gone, and nature’s palette is fading to a gray wash. What’s a naturalist to do? Delve into the mosses! I will share with you what I have learned so far and point to a few resources that have been helpful guides in this new exploration. Evolutionarily, mosses are primitive plants that are a step beyond algae but that lack the more sophisticated seed and flower structures that most plants use for reproduction. People tend to like them, perhaps because of their diminutive size and soft feel, but they also sometimes confuse moss with molds, mildew, lichens, the closely related liverworts, and the distantly related clubmosses. So what do you look for when examining what appears to be a moss?
Take an up-close look and see that the growing colony is made of individual strands or stems, closely packed together. Your first step is to separate out one or more of these strands and to soak them for a few minutes to amplify their identifying features. Then evaluate whether the single piece’s growth form fits into one of three categories:
- Acrocarps have stems that typically stand straight up, with sparse forks if any. The stems are packed tightly together like tufts of carpet.
- Pleurocarps have stems that tend to trail along the ground, branching freely and at wider angles. The individual plants twine together to form mats.
- Peat mosses have stems that stand upright and have branches in clusters of three or more that are often crowded at the tips. They are said to resemble mop-heads.
Your next step is to examine the shape of the leaves on the single strand you are holding. This will likely require a hand-lens (10x) or microscope. You must use your relative judgement to decide whether the leaves are hair-like, lance, tongue, or sickle shaped, or ovate. It’s okay if you can’t decide – I couldn’t either at first, so I scrolled through more sections of the identification guide than needed. It gets easier with practice.
The third step in helping to nail down an identification is to note whether the leaf has a midrib running down its center. Again, this will require a sight aid for most of us. There are a limited number of species bearing each combination of growth form, leaf shape, and midrib, so these three steps should help you to narrow down your options to a handful of candidates. Don’t be too quick to call the identity of your specimen – mosses are challenging and much of the fun is in experiencing them and teasing out their ambiguities.
I found these five common species on a recent foray into the Eastwoods Preserve, where they should be visible all winter except when hidden under snowfall.
I also found a few plants that were not mosses at all, although their names imply otherwise. The two species are part of a group that is more closely related to ferns and would be found in identification guides to the ferns and their allies. The last two are lichens, which are a symbiotic combination of algae with two kinds of fungi. They are environmentally sensitive, like mosses, and are easily disturbed, so please tread lightly around these fascinating life forms.
Beyond identification is a an entire field of study on the functions of moss in the web of life and on our landscape. While these primitive and ancient life forms have evolved enough defenses to be basically inedible, they have a long history as soil builders and environmental modifiers that help to stabilize ecology and provide a foothold for other lifeforms to thrive in otherwise barren places. They also photosynthesize and store carbon (especially important in arctic regions), absorb rainfall and runoff lessening erosion, and serve as habitat refuges for small organisms. Anthropogenically, they have proved useful for their antibacterial, antiviral, and antifungal properties in human medicine. They are certainly worth a look!
Resources to recommend for beginning learners include:
Regional guidebook for identification: https://www.amazon.com/Common-Mosses-Northeast-Appalachians-Princeton/dp/0691156964
Facebook group on Lichens, Mosses, Ferns and Fungi, with members from around the world, helpful with identification of lichens and mosses mainly: https://www.facebook.com/groups/172285406121262/about/