A retired English schoolteacher with a minor reputation as a photographer was once approached by an advertising agency executive to take some photos of a new strain of hybrid cabbage.
The former teacher, Harry Smith by name, turned up at the trial grounds with a simple roll-film camera, a close-up lens, and a tripod.
The color transparencies that resulted were so strikingly beautiful that they reshaped the ad executive's future. If Mr. Smith could turn the common cabbage into a thing of beauty with such simple equipment, then perhaps he, the executive, could do similar things with a camera.
Mr. Smith went on to become one of the world's foremost plant photographers and was commissioned to shoot the illustrations for the book ''The Rothschild Rhododendrons,'' a copy of which resides in the White House library.
Derek Fell, the journalist-turned-advertising executive in question, has since become an author with several book titles to his credit and a plant photographer with a growing reputation. His pictures appear regularly in gardening publications around the United States and in Architectural Digest. Next year the Digest is publishing a book of selected gardens featured in the magazine, and 16 of those chosen are the work of Mr. Fell.
One of Fell's recent books, ''How to Photograph Flowers, Plants & Landscapes'' (HP Books, 1981), is about to go into its third printing. To my regret I have had this book on my library shelves for the better part of 18 months without ever opening it. I didn't have the time, or so I thought, until last week. I should have made the time, for my own beginnings in plant photography last summer would have been much the better for it.
That early lesson in the fields of an English seed company has stayed with Mr. Fell over the years: Keep it simple, is the theme running throughout the book. This applies particularly to equipment. Up to a point, the less you carry around, the better.
For instance, Fell seldom uses a tripod, although he admits to its necessity on occasions. Fully 99 percent of all his published pictures were taken without such an aid. The point he makes is that cumbersome equipment limits your ability to shoot efficiently.
On one occasion, Fell climbed the slopes of the Koko crater, in the Hawaiian Islands. His goal: a magnificent clump of variegated century plants. It was arduous going, complicated by loose pebbles constantly slipping away from under foot. He climbed with the light roll-film camera strapped to his side. If he'd had more than that, he doubts whether he would have persisted.
As it happened, he returned triumphantly with the picture that appears on Page 4 of his book: Argave americana variegata, with the crater rim in the background.
The point Fell makes is that good picture composition is in the eye and mind of the photographer and that no amount of complicated equipment will change that. Hints on photo composition, frequently with examples, abound throughout the book.
This book is aimed primarily at the amateur photographer but it will help the professional, too, because it explains the type of picture that gardening editors and seed catalog producers are looking for.
''How to Photograph Flowers, Plants &Landscapes'' is found in bookstores under the photographic section or on the bookshelves of camera stores. Otherwise , write to HP Books, Box 5367, Tucson, Ariz. 85703 ($7.95, plus $1 for handling and postage).