Once I got the last of the garden leeks harvested, I started paying attention to some tiny plants that we have on our property but have mostly ignored until now. Those plants are small and require no work.

My new attention on lichens and mosses was sparked by books.

When I read a review coupled with an author interview about “Urban Lichens: A Field Guide for Northeastern North America” by Jessica L. Allen and James C. Lendemer, I was intrigued and ordered the book, which is published by Yale University Press.

My knowledge of lichens before I read the book was minimal. I’ve recognized lichens since childhood, seeing them at my various homes, in cities and forests. I didn’t know there were different kinds of lichens and, not knowing that, couldn’t tell one species from another.

From a tour of Denali that my wife and I took in 2018, we learned that lichens are plentiful in that part of Alaska, and in winter provide a major part of the diet of caribou, moose and deer. The book confirms this and says caribou disappeared from the Selkirk Mountains – where Idaho, Washington state and British Columbia meet – after intense logging eliminated most of the lichens.

In addition, some birds, including hummingbirds, and flying squirrels make nests from lichens and, when nesting season is over, eat the nest.

Though small, lichens are complex.

Lichens are “an intensive cooperation between a fungus and an alga or a cyanobacterium, and sometimes all three symbionts are required to form a lichen.”

Don’t worry, I had to look up some of those words. Alga is singular of algae, a simple non-flowering plant. Symbiont means participant, roughly, coming from the Greek symbiosis. Cyanobacterium is a bacteria that can perform photosynthesis, using the sun to create food the way green plants do.

That’s just the basic structure. Inside that skeleton are “bacteria, non-lichen fungi, microscopic worms, and water bears.” I had to look up water bears, too. Their scientific name is Tardigrads, and they are eight-legged, segmented micro-animals, which I translate as tiny bugs, but that could be wrong, technically.

Lichens as far back as 1807 – or 1791 if you count a poem by Erasmus Darwin, Charles Darwin’s uncle, in addition to technical writing – have been known to be sensitive to pollution. Botanist William Borrer wrote in 1807 that the air in London was so bad that lichens died.

Sulfur dioxide is the pollutant most dangerous to lichens, and scientists even now use lichens as one of the least expensive ways to “to determine both the type and severity of air pollution,” the book says.

It also notes that almost all of the lichens in New York City disappeared during the years of the worst pollution but are now making a comeback.

Most of the fun facts in the 158-page “Urban Lichens” come in the 20-page introduction, with the rest of the book providing descriptions of specific lichens and how to identify them.

Taking the book outside, I’m pretty sure I was able to identify three different lichens on our property: Mortar Rim, with the scientific name Myriolecus dispersa; Rock Whitewash, or Phlyctis petraea; and Common Greenshield, or Flavoparmelia caperata.

I will take the book out again when the weather gets warmer, and I might find more.

Because I had so much fun with “Urban Lichens,” I pulled out “Moss: Discover, Gather, Grow” by Ulrica Nordstrom, which was published and arrived in 2019, but I never got around to reading it.

Mosses aren’t quite as complicated as lichens, but they are different from other plants in that they have no real roots. They do have rhizoids, which anchor the moss to the soil, rock or wood where it grows. Without roots, moss gets its moisture and nutrition through pores in the plant’s leaves and stems.

As in the lichen book, “Moss” describes different species of moss, and will help you identify the mosses you see in your yard and travels. I had less success identifying the mosses on our property.

The book also explains how to transplant moss from places you find it – with permission, of course – to your own home and grow it. It includes many projects you can make with moss, including but not limited to moss terrariums.

Nordstrom devotes much of the book to describing moss gardens around the world, including some in the Northwestern United States. The author is Swedish, and much of the text involves mosses in Great Britain, which has different climate from Maine.

I’m going to keep both books handy when garden season resumes in the spring, to see if I can identify and maybe even cultivate more lichens and mosses.

Tom Atwell is a freelance writer gardening in Cape Elizabeth. He can be contacted at: tomatwell@me.com.