Mosses and lichens, though unobtrusive, are all around us—in the cracks of sidewalks and driveways, creating miniature gardens in mall and gas station blacktop, and greening our roofs. Gardeners have likely observed mosses in their garden beds and lichens on their garden furniture, and both on stones and trees. Some may see earth-dwelling mosses as nuisance intruders and lichens as odd scraps of indeterminant heritage. They are, however, sophisticated organisms working on behalf of the planet wherever they are, fixing carbon through photosynthesis, preventing erosion, and building soil. They are both flowerless, a state of affairs that caused Linnaeus consternation because he based his taxonomic system on the reproductive parts of the flower—the numbers of petals, stamens, and pistils. Indeed, it took several hundred years of close observation to figure out how the cryptogams, Linnaeus’ name for mosses and lichens, reproduce (cryptogam comes from the Greek word for “hidden marriage”). However, mosses, members of the plant kingdom, do have egg cells and sperm and reproduce sexually, while lichens, which are not members of the plant kingdom, proliferate in various ways, most of them asexual. Lichens are best defined as complex ecosystems—a symbiotic collection of a green alga, a dominant fungus (after which the lichen is named), sometimes a cyanobacterium, sometimes yeast fungi, and various other microscopic organisms. Fragments of moss and lichen circulate in the atmosphere finding niches in some of the most inhospitable places on Earth where higher plants cannot survive.
For this reason, they are often termed “cosmopolitan extremophiles.” Endowed with a superpower called desiccation tolerance, they can withstand extreme cold, at the poles, and extreme heat, in deserts worldwide, and long periods of drought. Facing poor conditions, they quickly shut off metabolism, entering a state of suspended animation. Just as importantly, they are able to almost immediately turn on the metabolic machinery of life in order to optimize capacity for growth when there is a change in conditions. How they redeploy enzymatic machinery so quickly is under study.
Identification of mosses and lichens is an art. The details of their ecological preferences and of their shapes, forms, and color, which are so appealing to our eyes, have taxonomic significance. It is advisable to carry a 10x hand lens, around the neck or in a pocket, when going on a moss-and-lichen walk. The hand lens will reveal the kinds of details of the leaf tip, the leaf edge, the midrib, etc. that distinguish different species. But even without a hand lens the three main groups of mosses can be distinguished—the upright, clump-forming types (acrocarps), the feathery, carpet-forming types (pleurocarps), and the water-loving sphagnum mosses. Lichens fall into a number of groups that vary considerably—the mint-green dust lichens that cover shady embankments, the crustose lichens that form barely perceptible mosaics on rocks and boulders, the foliose lichens that have leafy lobes, the fruticose lichens that are like little shrubs, and others.
Identification of mosses and lichens to species level requires dedication and persistence, and often higher magnifications only possible with dissecting and compound microscopes. Reading guides give one a sense of all the details that need to be considered for species identification. For mosses I suggest starting with Jerry Jenkins’s Mosses of the Northern Forest: A Photographic Guide, Sue Alix Williams’s Ecological Guide to the Mosses and Common Liverworts of the Northeast, and Karl B. McKnight et al.’s Common Mosses of the Northeast and Appalachians. Also, Robin Wall Kimmerer’s A Natural History of Mosses: A Natural and Cultural History of Mosses, while not precisely an identification guide, gives readers a feeling for how and where they live. For lichens, I suggest Jessica Allen and James Lendemer’s Urban Lichens: A Field Guide for Northeastern North America and Troy McMullin and Frances Anderson’s Common Lichens of the Northeastern North America.
Gardeners can encourage their presence in the garden by simply allowing them to remain where they have settled, and supplying rocks that have cracks and crevices to act as magnets. The great temple moss gardens of Japan are thought to have been serendipitous. During several centuries of neglect as temples fell into disrepair, mosses moved in and flourished. Deliberately planting moss while expecting a magnificent outcome is problematical as species have very specific preferences for soil, light, and moisture. Also, both mosses and lichens grow slowly, lichens sometimes only a millimetre a year. The Magical World of Moss Gardening by Annie Martin (aka Mossin’ Annie) and Moss Gardening: including Lichens, Liverworts and Other Miniatures by George Schenk will inspire those who want to use mosses and lichens in their gardens. Lichens cannot be grown in the horticultural sense. If they appear in your garden, do no harm and maintain their current conditions. Gardeners are perfectly positioned to be guardians of these valuable organisms.
Elizabeth Lawson is the author of Primrose (Reaktion Books 2019) and Moss and Lichen (Reaktion Books, 2025). Learn more about Lawson and her work at elizabethwinpennylawson.com.
This article originally appeared in the March/April 2025 issue of Upstate Gardeners’ Journal.
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