by David Allen Sibley
Alfred A. Knopf, 2009
Who knew? David Allan Sibley’s natural history interests do not end with birds. Nearly a decade after the appearance of the landmark Sibley Guide to Birds, we now have a bookend volume - same layout, same pliable cover, nearly identical dimensions - devoted to North American trees. And given the typographical dominance of the author’s name in the title, it looks as if the publisher hopes that Sibley will reprise for Knopf in this century the role Roger Tory Peterson played for Houghton Mifflin in the last: namely, that of a cash cow that – hold for the mixed metaphor – lays golden egg after golden egg.
Peterson and Sibley approach the art of field-guide illustration with distinctly different assumptions. Peterson, who essentially founded the field-guide genre, believed in paring to essentials; the guides he illustrated (or edited) rely on flat, schematic drawings. George Petrides’s leaf illustrations in the Peterson tree guide are two-dimensional, monochromatic outlines. Sibley’s leaves, aiming to be naturalistic, add topography, texture, and color. To be fair, the Petrides illustrations, augmented by text, will enable one to do the work of identification as well as Sibley’s; but you won’t lose much money betting that most people will prefer a guide that works at being visually pleasing as well as useful.
Every tree-guide author begins with a definition problem. Everybody knows what a bird is or what constitutes a snake, but what is a tree? Peterson/Petrides avoided the issue by adopting the big-tent approach: any woody plant would do. And so that guide treats shrubs and vines as well as trees. Sibley limits his subject to “any plant species that is commonly over 30 feet tall with a trunk at least one foot thick,” which means that a cactus (the stately saguaro) qualifies while smaller woody plants do not.
Shrub lovers will be dismayed at the short shrift given the dogwoods and viburnums, but tree-watchers who pursue their hobby in parks, on college campuses, and along residential streets will be delighted at the generous selection of exotics, whether naturalized or not, treated here. (Most tree guides, whether on principle or in response to space constraints, largely or entirely ignore introduced species.) Northerners can use this book to identify not only ginkgo and Scotch pine and Russian olive but also downy birch and shantung maple, and even an obscure member of the rue family called the beebee tree. Indeed, Sibley’s inclusiveness for most tree families is remarkable for a one-volume work; while Peterson/Petrides treat 27 oaks and the Brockman/Merrilees Golden guide includes 40, Sibley features 77 species, including Quercus carmenensis, known in this country from a single specimen discovered in the Chisos Mountains of west Texas. With a few exceptions – a suite of native species unique to south Florida is omitted, and a large, tangled complex of hawthorn species is generalized and sampled – the user of this guide can expect to find any native tree found in North America north of Mexico.
In addition to the handsome leaves, flowers, fruits, barks, and a sprinkling of full-tree silhouettes, Sibley writes useful introductions for each tree family, gives us tips for discriminating similar species (are those hitherto generic trees growing along your riverbank white ash, green ash, or black ash?), and adds an occasional note introducing tree problems and bird/tree associations. In addition to the usual tree-guide helps – a general subject introduction, an index, hardiness-zone and eco-region maps – this volume features a full species checklist and a time-saving, back-of-the book, one-page quick index.
Finally, a couple of caveats. The book jacket’s claim that the Sibley guide is “small enough to take into the field” is rather a stretch. At four times the weight of most field guides, this book is unlikely to be schlepped far afield. It will probably serve most users as a home- and car-based reference guide. And the Pennsylvania outfit responsible for the book’s color separations needs to explain why, all too often, tree parts correctly described as yellow in accompanying text appear on the page a bold, unapologetic orange.