AS JIM SUTTON guided a visitor through Longwood Garden's Christmas exhibit, he paused at a display of 12 poinsettias in a back corner of the main conservatory.

"This is a voluptuous one," he said, stopping to finger the leaves of a plant called "Vintage Red."

Sutton, Longwood's display designer, oversees events such as January's Orchid Extravaganza and the Chrysanthemum Festival in fall. But his biggest job by far is A Longwood Christmas, the annual explosion of lights, trees and poinsettias that jams traffic in sleepy Kennett Square every December.

This year's theme is "A Gingerbread Fantasy," so visitors will see trees decorated with cookies in the conservatory's Exhibition Hall. An artificial gingerbread scent is pumped into the Music Room, which features trees made of gingerbread shingles, a train painted gingerbread brown and gingerbread re-creations of the conservatory and the du Pont home - the ultimate gingerbread house. Even the Tropical Terrace gets into the act, with an exhibit of plants that produce gingerbread ingredients: ginger, sugar, cinnamon, allspice, and cloves.

Themes allow the designers to tweak the traditional holiday tropes of trees and lights. But it's in the artistry of the poinsettias, 2,000 of them this year, that A Longwood Christmas really distinguishes itself.

For Sutton, poinsettias are his design medium. Although a poinsettia does have flowers, they're small yellow nubs. The iconic red and white of the plants are actually modified leaves called bracts.

He admired the rich red leaves of the "Vintage Red," one of the dozen plants being grown at Longwood as possibilities for future Christmas displays.

As display designer, Sutton gets his pick of the poinsettia litter. Every year, he studies the new varieties offered by growers and brings some to Longwood. He grows three plants of each variety to evaluate their color, density and predictability. Not all poinsettias, he said, will develop their promised colors. "Christmas Feelings Dark Salmon," for example, had lush red leaves, but also crisp white leaves, and some graphic leaves that were half red and half white. It would be hard to predict how that one would look in a display.

Of the varieties in this year's trial, the most promising member is the stunning if unfortunately named "Luv U Pink." The bracts of "Luv" are so vibrantly pink that they appear almost neon. The plant did not have the standard bush shape of most poinsettias, but instead undulated like a Japanese maple. Visitors stopped to take pictures of this show-stopper with their cellphones.

"I think you'll definitely see this one next year," Sutton said.

In the beginning

Unlike the Christmas tree, the poinsettia has no religious connection to the holiday. Its status as a seasonal symbol is purely a commercial affair. Poinsettias, whose scientific name is Euphorbia pulcherrima, are native to Mexico and the plant was brought to the United States by the country's first ambassador to Mexico, Joel Roberts Poinsett, in 1828. The next year, it was displayed to the public for the first time at the Pennsylvania Horticultural Society's inaugural Flower Show.

The ubiquity of the poinsettia is attributed to the Ecke family of California, growers who relentlessly marketed the plant through magazine spreads and TV programs such as "The Tonight Show" and Bob Hope's Christmas specials. Today the plant is the most popular potted plant in the country, according to the U.S. Department of Agriculture.

Longwood Gardens has been growing them since the 1920s. According to the encyclopedic "A Longwood Gardens Christmas," by Colvin Randall, founder Pierre du Point and wife Alice started hosting lavish Christmas parties for employees in 1921. After du Pont died in 1954, the Gardens became an exclusively public site, and Christmas at Longwood began a tradition that would eventually transform from a slow-season draw into the garden's most popular attraction.

While visitors memories of the show endure, not so the poinsettias.

Unlike other popular potted plants like African violets or orchids, the poinsettia is not built to last. According to the University of Illinois' Poinsettia Pages website, "With care, poinsettias should retain their beauty for weeks and some varieties will stay attractive for months."

That's "with care." Inevitably, the plant meets its fate in the trash can, about the same time the holiday tree comes down. The poinsettia is the plastic of the horticultural world.

That Longwood can do interesting work with the poinsettia is a bigger testament to the Christmas show's artistry than the number of gingerbread cookies on display (8,000), the work-hours behind the gingerbread houses (350), or the size of the outdoor light display (500,000 bulbs). The successful display of poinsettias reaffirms Longwood's status as one of the world's pre-eminent gardens. More importantly, it reinforces the function of the botanical garden itself: This is not a passive repository of plants, but a site where plants are actively deployed for aesthetic purposes.

In the process, visitors are able to see poinsettia forms and colors and patterns they would never otherwise encounter, not because they're exotic, but because they don't generate revenue for the industry. In fact, Longwood maintains a stock of poinsettias so that it doesn't lose varieties it likes - for example, varieties that look good in both natural and artificial light - when they are taken out of commercial cultivation.

One might think that Longwood's endorsement of a poinsettia variety would have value in the industry, but Sutton said the commercial growers aren't interested in what works for Longwood. Looking out across the Main Conservatory, he pointed to the rows of "Visions of Grandeur," which climbed toward the high glass ceiling. Sutton needs some poinsettias to grow tall; short plants won't work alongside the room's tall columns. And growers don't want tall plants.

The reason speaks as much to Longwood's unique place as it does to the intersection of nature, holidays, and capitalism: A tall poinsettia, Sutton said, "won't ship, and that's not going to work for Walmart."

Art Attack is a partnership with Drexel University and is supported by a grant from the Knight/NEA Community Arts Journalism Challenge, administered by the Greater Philadelphia Cultural Alliance. "