FLOWER POWER

WHO visits flower shows nowadays? They're youngish. They bring kids. They wear sweatshirts with pro-compost slogans. They point at perennials and say, "What's the Latin name for that?"

Here at the Philadelphia Flower Show, the greatest indoor display of blooming plants in the world, the annual symbol of mankind's triumph over sleet, labels that just say "daffodil" aren't good enough anymore. Baby boomers have discovered gardening, and they want specifics.

The 30- and 40-something couples that now throng flower show aisles are in search of hard knowledge to help their own landscape. They like denser flower displays. Lower-maintenance plants. Environmentally sensitive growing techniques. Historical associations.

The perfect baby-boomer plant: a 16th-century strain of delphinium that blooms nine months a year in the desert with no pesticides and crawls by itself to the compost heap every October.

"The 30-somethings just love compost," notes Lisa Stephano of the Pennsylvania Horticultural Society, the organization behind the Philadelphia show.

A small display here, tucked to the side of the entrance escalator, is evidence of the change that is coming to this sanctum sanctorum of horticulture.

Amid the garden clubs and nursery fantasies and bonsai collections is an exhibit distinguished by its many varieties of lettuce.

It's been put together by the Rodale Research Center Institute and its associated publication Organic Gardening magazine, who have been lured to the Philadelphia Flower Show for the first time. Pretty much everything in their display is edible.

"Lettuce is a very ancient vegetable," says Cheryl Long, research editor of Organic Gardening. "Caesar put up a statue to lettuce."

At this point, a reporter refrains from making an obvious pun involving salads. Ms. Long is cheerfully serious about her gardens, after all. Organic Gardening and the other parts of the Rodale empire have long been the great American proselytizers for agriculture without chemical fertilizers or pesticides. As environmentalism has gained popularity with the young they have become prophets inheriting a movement.

Where most exhibitors here use sawdust mulch for the "soil" of their gardens because it's light and easy to handle, Organic Gardening is using good black compost. Every day at 1:00 p.m. they release a swarm of aphid-eating ladybugs, to make a point about natural pest control.

Actually, aphids are somewhat scarce in the Philadelphia Civic Center interior. Thus to keep the ladybugs happy "we've put special food in little dishes among our plants," admits Long.

Except for their food pails, the ladybugs will likely find it hard to distinguish their environment from the outside world. This past week, a six-acre hall that normally hosts less colorful conventions has been graced with an artificial spring.

Blue ageratum nestles against creamy coreopsis under a weeping cherry; a giant Victorian urn looms ahead filled with lilies in all the range from pink to white; rhododendrons everywhere provide a violet-blue; foxgloves stand four feet or more with each spotted bell the size of a small saxophone.

Never mind that in nature these plants don't bloom at the same time; this is June as we would have it be.

With some 220,000 attendees expected, the Philadelphia Flower Show is easily the largest in the United States. The Chelsea Flower Show in London is bigger, with some 15 acres of displays. But it takes place partially outdoors, with many of the plants blooming naturally.

In Philadelphia, by contrast, thousands of flowers have to be tricked into blooming. This is a little harder than forcing an amaryllis bulb in a closet. Among other things, it involves a little artificial winter.

"Last August these went into the refrigerator," says Chuck Gale, of Gale Nurseries Inc., sweeping his hand at a riotous border garden. The Gales - Chuck and his father Charles - are masters of forcing. Their technique involves carbon dioxide emitters to match the changing atmosphere of spring, special lights, and different temperatures for soil and air, depending on the plant. You can't do it at home.

LONGTIME exhibitors, the Gales worked with the National Trust for Scotland to construct this year's Philadelphia Flower Show central feature. It's a kind of medley of famous Scottish gardens. In front, appearing before your eyes like a stage set as you descend the escalator, is the "Lion Parterre" of the Great Garden at Pitmedden. This is a lawn set with a geometric design etched by boxwood, marigolds, and dusty miller.

Behind the Parterre's flagstone wall is the Garden of Crathes Castle. This is a 50-foot border, much of it composed of sweet cottage plants.

The effect of the whole thing is something like that of reading several dozen of the fancy gardening catalogs (Smith & Hawken, White Flower Farm, etc.) that are aimed at baby boomers. One's heart is filled with longing for flowers one's head knows will fry like pork chops in the savannah that is your lawn.

Chuck Gale says he and his father began nurturing some of the shrubs in the 7,000 square-foot display two years ago. Most of the plants involved were grown just for the flower show. Sure, it's expensive. But you never know when a well-heeled 40-something will ask you to duplicate a display at his home in the Hamptons.

"This is business for us," says Gale.

During the week the flower show runs, June quickly segues into July. Flowering trees bloom and leaf in the heat created by lights and thousands of spectators. So how do displays look nearly as fresh the last day as the first?

The secret is the show offers a cash award to the best maintained exhibits. Some delicate flowers get replaced every night.

"Daffodils are the worst. They want to start flopping by the end of the day," says Daniel G. Kepich, a nursery owner whose vibrant patio garden looks as if it wouldn't dare wilt.

* The flower show closes this Sunday.