DECATUR, Tenn.— PETER THEVENOT, nurseryman and arborphile, calls himself ''a gnarly-bark guy.'' On a Saturday morning last October, he steered his pickup truck toward a lichen-covered river birch near the bank of Big Sewee Creek, which joins the Tennessee River on the edge of his 340-acre farm here. The birch's peeling bark was reddish-brown, tan and white, with the texture of parchment. ''Isn't that cool?'' Mr. Thevenot asked.
Most people admire trees for their leaves or blossoms. Mr. Thevenot says he loves them for their hides. ''Flower color is just so fleeting that if that's all you're buying a tree for, I think you're really in for a huge disappointment,'' he said.
Mr. Thevenot resembles Ralph Waite during his days playing John the elder on ''The Waltons,'' and his voice discloses his Cajun roots in southern Louisiana. ''The interesting thing about bark,'' he added, ''is that you're usually dealing with a plant that you're going to have to stay with for a long time before it begins to show you all its little secrets.''
The trees at Mr. Thevenot's nursery, River Road Farms, confide in their keeper in unusual ways. He is one of a handful of growers in the country who specialize in espalier, the ancient and all but forgotten art of training fruit and ornamental trees to grow flat against a wall or fence, sometimes forming extravagant architectural shapes. In this rarefied form of horticulture, the trunks and limbs of trees are the only lines the artist has to work with, so the bark that covers them gives the final work its character.
Mr. Thevenot, 58, is making it his life's mission, he said, to bring espalier back to the public eye. In rows across one big flat field, he keeps some 1,300 trees trained up against miles of high tension hog-wire grids -- a material normally used to fence in swine. With his guidance, the plants grow flat, in two dimensions rather than three, to resemble crosses, candelabras, tuning forks or palmette fans. One apple tree is taking the shape of a heart. On part of his proving ground, Mr. Thevenot is training two parallel rows of trees along a wire frame to form an arcure, or arched enclosure, about eight feet high.
Up the hill, outside the stately, two-story stone house where he lives, Mr. Thevenot has a Belgian fence of trees he marshaled into a woven-basket pattern, 7 feet high and 40 feet across. He's growing Golden Delicious, Red Delicious, and Arkansas Black apples. He grows pears, too: Bartletts, Shinko Asians, Kieffers and nonbearing Bradfords. And there are the Prairie Fire crab apples, with their maroon shoots and clusters of crimson fruit. ''They make the most beautiful wood and colors, but they are so slow to trunk up,'' he said.
Because espalier takes years to mature into its fullest glory, it can -- as it has for Mr. Thevenot -- turn into a lifetime pursuit for the devoted, whose numbers, based on anecdotal evidence, appear to have increased over the last several years. The espalier revival is on.
''Espalier is hot,'' said Dean Norton, the horticulturist at Mount Vernon, George Washington's estate on the Potomac near Alexandria, Va. ''It's great fun, and what's really nice about it is that it takes a watchful eye.''
Wendy Proud, product manager for Monrovia, a wholesale nursery in Azusa, Calif., said that though espalier largely fell out of popularity in the 20th century, it has been staging a comeback as gardeners look for new -- if old -- ideas, especially for tight spaces.
In 1988, Mr. Thevenot sold his occupational-training business in Baton Rouge, La. He and his wife, Beth, bought this farm near Decatur, the seat of Meigs County, which nestles in the softly rolling hills of the Tennessee River Valley about midway between Knoxville and Chattanooga. He left behind the expense-account life and ''28 pounds of neckties'' for fresh meals, good wine and a snort of bourbon now and then.
Four years later, Mr. Thevenot planted his first young fruit trees and began selling the best ones four years after that, once he had whipped them into espaliered shapes. Since then, Mr. Thevenot's business has grown handsomely. In 1996, he gave away samples of his first available batch. The next year, he sold 35 trees. This year, he sold about 350, mostly to professional gardeners and landscape designers, but also to individual gardeners. The trees generally cost $225 to $375 each -- and more for the most complicated types.
Espalier came as a revelation to Mr. Thevenot. He had been trying to run an all-purpose nursery for several seasons by growing oaks, crape myrtles and magnolias. But on a trip to Mount Vernon in the early 1990's, he discovered several robust pear and apple cordons, a subtype of espalier trained as a living fence. They lined the beds of the estate's sunny kitchen garden, which are carpeted with a gravel of crushed Chesapeake Bay oyster shells, just as they were when Washington lived there.
Still other espaliered trees were climbing the garden's walls. The Mount Vernon Ladies' Association, the nonprofit group that owns and maintains the house and grounds, had its oldest cordons installed in 1937.
