Grass and its relatives are among the most important plants in the world – Maine included.

Grasses minimize erosion, store floodwaters and are “important for a diversity of animals providing food, cover, nesting materials, perches, and reproductive sites, among other things,” said Don Cameron, one of four authors of the just-published “Grasses and Rushes of Maine.” His co-authors are Glen Mittelhauser, Matt Arsenault and Eric Doucette.

The new field guide is a companion to “Sedges of Maine,” published in 2013, and with the two books most people should be able to identify any graminoid (the scientific term for grass-like plant) in Maine.

Grasses are everywhere, or more precisely as Cameron said, they are only “uncommon in acidic bogs, highly shading forests (i.e., under hemlock), and are absent from water deeper than about 3 feet.”

Among the most important grasses, Cameron believes, are one, the spartina species that make up a large part of the salt marshes that protect the shoreline from stormy seas, and two, the Canada bluejoint grass, Calamagrostis canadensis, which is widespread and does similar work in freshwater.

The book uses dichotomous keys – a series of either/or choices – to help readers determine the identity of a plant. The first key is to decide if the plant is a grass, a rush or a sedge – and the book goes well beyond the common mnemonic “sedges have edges, rushes are round and grasses are jointed all the way to the ground.”

If it’s a sedge, the key refers readers to the earlier book. If it is a rush or a grass, it will be in this book.

Mittelhauser, who works at the nonprofit Maine Natural History Observatory that holds the copyright for the two books, admits that the plants covered can be tricky to identify.

“The way the keys are set up, it gives farmers or people who just like the outdoors a lot of ways identify an unknown grass,” he said. The farmers would want to know what grasses make up the hay they are harvesting, he explained.

I’ve had trouble using dichotomous keys in the past, but this guide includes high-definition, color pictures to show what bracts, florets, outer tepals or other features of the plants look like. The entire book is on high-quality, glossy paper so the plant parts show up clearly.

Despite the authors’ best efforts, it is still easy to go astray, Mittelhauser said. That is why when you have come to the point where you, the user, decides which genus of grass you think it is, the book provides pictures of similar genera, so you can compare the plant in the hand to two or more in the book.

By sheer numbers, grasses (botanically Poaceae) outnumber rushes (Juncaceae). Two genera of rush exist (Junca and Luzula) while there are 63 grass genera. Worldwide, 408 rush species exist, with 34 in Maine, compared to about 11,000 grass species worldwide with 215 in Maine; another 40 used to be here but probably aren’t now.

While there are other grass and rush identification guides around the country, no equivalent exists to this publication for any other single state, Mittelhauser said. And while this volume would be useful to people who live nearby – a list of New England states and nearby Canadian provinces where each species is also found is included in the distribution and habitat section for each species – it will be much less valuable for people who don’t live nearby.

The comments section on each species includes whether a species is considered endangered or threatened. I asked Mittelhauser if people should be worried that the state has only a few examples of the Northern wood rush, which is listed as endangered, and the spiked wood rush, which is listed as threatened. The book says the only places these two species have ever been found in Maine is on Katahdin, and I figured that’s because they don’t belong anyplace else. Mittelhauser replied the designation is mostly there so people will keep an eye on the plants.

Mittelhauser said it was fairly easy to decide what each of the four authors would cover in researching “Grass and Rushes of Maine” because each has different areas of expertise. Cameron works as a botanist for Maine Natural Areas Program, an agency within the Department Agriculture, Conservation and Forestry; Arsenault works as an environmental associate at Stantec, a global design consulting company with an office in Scarborough; and Doucette earned his doctorate at the University of Maine and is now an assistant professor of biology at the Massachusetts College of Liberal Arts in the Berkshires. The book was under peer review for about a year before it was published, which involved others educated in botany using the guide in the field to try to identify grasses and rushes they found. Mittelhauser also praised the University of Maine Press for its work. The press printed 1,500 copies in the first run, he said, and the book is now in its second printing.

Mittelhauser is looking forward to hearing from people who use “Grass and Rushes of Maine” this summer. Their feedback, he said, may help drive clarifications and corrections in future editions.

He has already found some corrections of his own he’d like to make.

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

tomatwell@me.com