CITY OF TREES The Complete Field Guide to the Trees of Washington, D.C. Text by Melanie Choukas-Bradley Illustrations by Polly Alexander Photographs by Melanie Choukas-Bradley and Polly Alexander The Johns Hopkins University Press. 354 pp. $12.95

By now we have all heard enough about the unpredictability of Washington weather -- this having to do with our geographical position, both north-south and east-west, and the influence of the mountains and sea. In the matter of trees there can be no doubt how fortunate we are: That same geography and transitional climate have given us a city of trees, a region of trees, without rival. Not only are we in the range of both the southern and northern trees, but the circumstances are also right for transplanting the handsomest varieties from Japan and Korea, China and Albania (natural habitat of the common horse chestnut).

With "City of Trees," Melanie Choukas-Bradley, who wrote the text, and Polly Alexander, who did the drawings, have created a splendid field guide -- practical, botanically sound and filled with good stories.

The book consists of a concise arboreal history of Washington since L'Enfant's time; a guide to tree-viewing locations; and a long botanical guide in which several hundred native and exotic trees found in the city are described and depicted in drawings of leaves and fruit. Several useful lists and a glossary are at the back of the book. There are also two dozen color photographs of flowering trees.

The best locations for tree viewing: From a historic standpoint, Mount Vernon, the grounds of the White House and the Capitol and Cedar Hill (the home of Frederick Douglass) are recommended. All have a fine variety of trees and shrubs. In fact the authors call the Capitol grounds "one of the world's finest arboretums." Of course the National Arboretum has everything, including peaceful drives and walks, and easy parking most of the year. Roosevelt Island (like the National Zoo, a natural woodland setting) is a perfect place to hike uncrowded trails and practice tree identification.

Choukas-Bradley's historical stories quite naturally emphasize the presidents and other political notables, but the two men most responsible for replanting the city (for most of the original forest was long gone) get their due recognition. Alexander Shepherd, second and last governor of the District, had thousands of trees planted in the early 1870s. During that same period and into the 1880s, Frederick Law Olmstead, America's greatest landscape designer, planned and directed the wonderful and enduring tree plantings on the grounds of the Capitol.

We learn that Alexander Hamilton's favorite tree was the sweet gum and Thomas Jefferson's the willow oak. But I think Choukas-Bradley's tribute to George Washington as a great lover of trees and an expert in their culture is especially appropriate. A number of his own plantings at Mount Vernon survive. These are tulip trees, American holly, ash and a buckeye, strikingly representative of his life and interests.

Books about trees have a long and honored tradition in this country. Some of the best are works of literature of high order (and scientifically excellent, too). But in the end we have to judge a field guide by its success in meeting its basic purpose, which is to give an accurate, useful description of the natural object. Choukas-Bradley and Alexander have done everything possible to help. Their descriptions are enthusiastic, and their identification keys actually work. And they won me over with their praise for the glories of the black locust. Look for it: fragrant white flowers in May; wondrous shade all summer. But better look it up first, as the foregoing description won't quite do: Page 248 in "City of Trees."

The reviewer, a former Air Force officer, frequently writes on historical and literary topics.