Homages to trees, in form and metaphor, have appeared in art, music and poetry for millennia. “And this life of ours, free from public bustle, / Finds tongues in trees, books in the running streams, / Sermons in stones, and good in all,” wrote Shakespeare. Trees of knowledge and trees of life have deep taproots in human culture. And if trees really had tongues, they could tell the story told in the opening chapters of Smithsonian Trees of North America: of shrinking habitats, steep climate changes and even extinction.

The book is the work of a decade by W. John Kress, 1973, a distinguished scientist and curator emeritus of botany at the Smithsonian’s National Museum of Natural History. Now based in Vermont, he has spent most of his career studying tropical plants. But in the early 2000s, he began thinking about putting together a book on North American trees. He was already well underway on the project, crisscrossing the continent to photograph the last of the 326 native and introduced tree species featured in the book when COVID restricted travel. To survive the lockdown, he writes in the acknowledgments, he turned to botanical colleagues around the world, who sent him specimens by express mail that he could photograph in his home studio.

The result is stunning. Silhouetted against a rich, black background, the photographs elevate tree fruits and blossoms, buds and branches, leaves and seeds to an art form unmatched by any other. Along with the detailed descriptions of each species, they help identify trees common across the North American continent. Many of the images were originally compiled while the author was working on a free tree-identification app for smartphones called Leafsnap (no longer available; Kress instead recommends iNaturalist, a crowdsourced alternative for identifying plants, animals, insects and fungi). But this beautiful book is not intended to be a field guide—at least not in its 800-page physical form, which weighs a whopping 6 pounds (for portability, consider a second copy in one of the digital formats that will be available upon release). Instead, Kress hopes the book will inspire readers to with trees.

Each entry on the species, listed in order from oldest to most recent evolution, includes numerous photographs, Latin and common names, a distribution map, a physical description, a discussion of their use and value, their ecology, their vulnerability to climate change, and their conservation status. What sets Kress’ book apart from existing field guides is that the photographs were taken, selected, and presented with an eye for morphological differences—critical for distinguishing related species. Still, identifying trees can be complicated. Kress introduces readers to leaf shape, structure, and orientation, the appearance of bark and wood grain, and the variety of cones, flowers, and fruits. Leaves are the best first clue, but as he admits, one consequence of evolution is natural variation, which can sometimes be misleading. Fruits and seeds—”the glue that holds forest communities together”—also help with identification, but learning about their variation can be “overwhelming.” The Number of seeds For example, distinguishes between a drupe (one) and a berry (many), but what distinguishes a pome from a follicle, nut, winged fruit, or capsule? Kress helpfully compares these fruits by arranging photos of each shape side by side on a full page, as he does for cones, flowers, and inflorescences.

Cress, who received the 2021 Sargent Award from Harvard’s Arnold Arboretum to support his research for the book, wrote it for three reasons, as he explains in the foreword. First and foremost, he believes knowing the names of the trees they encounter will enrich people’s lives. Identifying the species is a first step.

His other goals perhaps reflect his training as an ecologist. First, he answers the question: What do trees do for people? He hopes to give “readers a sense of the value of trees” to them personally, and to highlight the role trees play in maintaining the health of forest communities, ecosystems, and the planet in general. In the foreword, conservation biologist Margaret D. Lowman enumerates their many benefits. In addition to hosting an estimated half of the planet’s terrestrial biodiversity, trees provide “medicine, food, wood, shade, climate change, soil protection, oxygen, energy production, and a spiritual heritage,” she writes, “for over two billion people on Earth who practice religions that seek refuge in forests.”

If recognizing the ecological benefits trees provide to humans is one facet of a mutualistic relationship, the other is human understanding of what trees need to survive. This, Kress says, was his final impetus for writing the book. With exceptional clarity and authority, he lays out the case for conservation and offers a basic introduction to tree morphology and ecology. The explicit subtext of the complex diversity of tree reproductive strategies (human sexual activity is mundane compared to tree sex and asexual reproduction) is that many tree species and the ecosystems they support are vulnerable to human environmental interference.

Kress briefly discusses the nature of this vulnerability. While there are an estimated three trillion trunks (individual trees) worldwide—half as many as before agriculture began 10,000 to 12,000 years ago—most trees are made up of a small number of species. In the Amazon, for example, 1.4 percent of species make up half of all trees. “It is astonishing that the other 98.6 percent of tree species in the Amazon are mostly rare,” he writes. “Many have not yet been discovered or described by botanists.” Astonishingly, an estimated 15 billion trees are lost each year, Kress reports. The main threats are habitat loss, commercial exploitation, pollution, urbanization, invasive species, and the spread of animal and plant diseases and pests.

While the scientific case for protecting forests is compelling—a natural forest, with its complex web of plant diversity, for example, stores up to 40 times as much carbon as a comparable area of ​​tree plantations (see “Plants on a Changing Planet,” May-June 2024, page 38)—nurturing a deeper human connection to trees requires more than just facts. And that’s exactly what Kress wants to achieve. with Smithsonian Trees of North America in photos and words. The introductory chapters are peppered with pop culture references—the song “Hickory Wind,” co-written by Gram Parsons ’67 (see “Sound as Ever,” July-August 2023, page 44); a poem about poplars by Gerard Manley Hopkins—and reflections on what it means to know a tree. Chapter five, on tree naming and identification, begins with a quote that aptly sums up one of the book’s main goals: “Knowing the name of a tree is the beginning of an acquaintance—not an end in itself,” writes Julia Ellen Rogers in The tree book. “You can spend the rest of your life with it. Friendships with several trees are something very precious.”