Although gardening has many aspects, and gardeners have special interests, the single incontrovertible fact is that everything begins with plants. Whether you are a new gardener or a longtime expert, whether you collect books and articles on your favorite subject or want a single volume that you can refer to today and twenty years from now, you need an encyclopedia of plants. In many ways this book is the culmination of the series of Taylor’s Guides that began in the 1980s, inspired by horticulturist Norman Taylor, whose classic garden encyclopedia was first published by Houghton Mifflin in 1936 and last revised in 1956.
As with all of the Taylor’s Guides, the aim in this book is to be thorough, accurate, dependable, and useful to North American gardeners. As we have shown in the plant guides, as well as in the other Taylor’s books, it is quite possible to make a practical reference book attractive and pleasurable to use. The text is readable, and the pictures and layout are beautiful. Like gardening itself, this book will give you immediate joy as well as long-term rewards.
HOW THE PLANTS ARE ARRANGED
To make this book useful to both experienced and novice gardeners, as well as professionals, the plants are organized alphabetically by genus name. A genus is a group of plants that share a certain number of characteristics. Within the genus are species, and the species name refers to only one plant. A genus may have a single species or it may include hundreds. The genus Cornus, for example, has a number of trees: flowering dogwood, Cornus florida; Pacific dogwood, Cornus nuttallii; pagoda dogwood, Cornus alternifolia; and several others. It also has shrubs, such as red osier dogwood, Cornus stolonifera, and the elegant little ground cover Cornus canadensis, or bunchberry.
This system of terminology is easier to use than it sounds; to find any of these plants in the encyclopedia, all you need to know is its common name. The index of common names (page 431) will lead you to the botanical name of the genus that the plant belongs to, which you can find listed alphabetically. “Dogwood” or “bunchberry” will lead you to Cornus, and there you will find entries for all of the Cornus species covered in the book.
Why not arrange the encyclopedia by common names in the first place? The reason is that although common names are often charming and descriptive (and none of us is likely to call a marigold a Tagetes), only the botanical name identifies the exact, specific plant. In this book there are at least ten very different plants whose name begins with the word “false,” such as false indigo and false Solomon’s seal, and five that begin with “glory.” “Ironweed” could be Ostrya, a tree, or Vernonia, a wildflower. Is the plant you admired in a friend’s garden love-in-a mist, love-in-apuff, or love- lies-bleeding? Or might it be bleeding heart? Harry Lauder’s walking stick (named for an early-twentieth-century British comic entertainer) is both descriptive of this corkscrew shrub and easier to remember than Corylus avellana ‘Contorta’. Poached-egg plant is certainly a more colorful name than Limnanthes douglasii. And I’d hate to see names like lion’s ear and tidy tips and blue-eyed grass disappear from the gardener’s vocabulary. But when you are looking for accurate information, you need to know what plant you are talking about. Is your prince’s feather an Amaranthus or a Persicaria?
Look up any of these names in the index of common names, and you’ll be referred to the genus to which the plant belongs. In the entry you’ll find a description of the species and an illustration to help you identify the plant in your friend’s garden. Should you want to grow it yourself, you’ll learn whether it will survive in your climate, how to plant it, and what further information you need to know to succeed with that plant. You’ll also find the names of hybrids and cultivars that may be improvements over the species. (In the glossary on page 424, you’ll find definitions of the terms hybrid and cultivar and of many other botanical terms used in this book.)
HOW WE DECIDED WHICH PLANTS TO INCLUDE
In an encyclopedia like this, more is not necessarily better. We have included at least one thousand species of desirable plants for American gardens; to list all available species would require a volume as large and unwieldy as a Manhattan phone book. We have obviously had to make choices, based on the knowledge and experience of the Taylor’s Guide editors. For example, you’ll find here the dawn redwood, Metasequoia — once thought to be extinct but now available as a desirable garden tree — but not the Sequoia, the tallest tree in the world, or the massive giaant sequoia, Sequoiadendron, both of which are recommended mainly for public parks and large estates.
Some plants are not recommended for hhhhhome gardens because they are invasive, but deciding which ones to eliminate turned out to be a rather complicated issue. A handsome perennial like purple loosestrife (Lythrum) does not appear in this book because the plants are such rampant invaders of wetlands that some states actually ban them; even the supposedly sterile cultivars have been found to set seeds. Some popular genera include species that are invasive and species that are not, as well as some that are problematic in one part of the country but not in others. Some common plants that fall into these good/bad categories are privet (Ligustrum), bittersweet (Celastrus), burning bush (Euonymus), barberry (Berberis), and honeysuckle (Lonicera). Before you decide on a plant for your own property, be sure to read the entry for that species. Readers who are concerned about this subject should consult the handbook Invasive Plants, published by the Brooklyn Botanic Garden.
Will the plant you are considering grow where you live? For gardeners, this is the question that matters most. If you do not know the plant zone of your geographic area, look at the U.S. Department of Agriculture Plant Hardiness Zone Map on pages 446–47. The zones range from Zone 1, the coldest, to Zone 11, the hottest. (In a new map, scheduled to be published in 2003, the major changes are the addition of the tropical zones, 12 through 15.) No zones are given for annual plants, which live for one growing season only, no matter what the climate. You’ll also find some plants listed as tender perennials. Although these will live and rebloom in succeeding seasons in warm or tropical zones, in most parts of the country they are grown as annuals.
Except for annuals and tender perennials, the plant descriptions give a range of zones. The first number in the range indicates the northern limit of hardiness, while the second is a guideline to how much heat the plant can handle. For example, peach-leaved bellflower (Campanula persicifolia), hardy from Zone 3 to Zone 7, is fairly cold-tolerant: it withstands Zone 3 winters, with average annual minimum temperatures of -30° to-40°F. But it is not particularly tolerant of heat and doesn’t grow well in the hot summers characteristic of areas south of Zone 7.
The northern limits of the zone ranges are based on average minimum temperatures taken from 6,700 weather stations and do not include any of the other variables that can affect a plant’s hardiness, such as a freak ice storm, an unusually warm winter, a year of drought, or being planted next to a south-facing brick wall. A good predictor of a plant’s success in your garden is finding it in other gardens in your area. But the USDA Zone Map is a useful place to start, especially if you are considering a tree or other valuable plant. The second number in the zone range, the southern heat limit, is based on the experience of professional growers and gardeners. If your own garden has a cold microclimate, you may be able to succeed with that Zone 3 to 7 bellflower even if you live in Zone 8.
At the very least, gardening is an enjoyable pastime; at the most, it is a passion. To all who use this book, we hope it will fulfill your needs and increase your pleasure.
— Frances Tenenbaum
Copyright © 2003 by Houghton Mifﬂin Company. Reprinted by permission of Houghton Mifflin Company.