Like a root-bound plant suddenly transplanted to a larger pot, the Philadelphia Flower Show opened this week in new and bigger quarters. The week-long event - the world's largest indoor exposition for the flower trade - runs through March 3 here at the city's new convention hall.
''We really needed the room to spread,'' says Lisa Stephano, spokeswoman for the Pennsylvania Horticultural Society, which sponsors the annual event. After 30 years displaying flowers and plants in an aging hall on the edge of the city, the show's exhibitors this year have been able to take advantage of the new location's higher ceilings, better lighting, and expanded space.
''The location's much better,'' says Michael Petrie, flower-show designer for J. Franklin Styer Nurseries in Concordville, Pa. The nursery has displayed its artistry here since 1893, the oldest exhibitor in the show this year. This year, Styer has created an imaginary garden that is pure whimsy. Palm trees compete with annuals, four new award-winning roses share space with Florida air plants, which are set around huge sand sculptures of a dragon, a fairy-tale castle, and a huge face.
''Here, you can do anything you want - no holds barred,'' Mr. Petrie says. There are no clients to please, no budgets. ''It's our biggest advertising expenditure of the year.''
The 59 nurseries and other major exhibitors at the show hope to attract the eye - and eventually the business - of the more than 200,000 visitors who file through the event each year. The show is displaying new flowers commercially available for the first time this year, including a pink hybrid known as the ''Cadillac'' rose, another pink variety known as the ''Royal Bonica,'' and the wine-colored ''Woodstock'' hyacinth.
The Altar Guild of the Washington National Cathedral has re-created the structure in miniature surrounded by a garden. The Zoological Society of Philadelphia is displaying some of the more than 200 species of trees in the nation's oldest zoo. A collective of 36 local gardens and arboreta have re-created a Palladian temple that stands in a local arboretum and a river view of the farm- house and garden owned by John Bartram, an 18th-century botanist who lived in Darby, Pa.
Because the show is now located downtown, instead of on the edge of the city, the rest of Philadelphia is getting into the act too.
The local Foundation for Architecture is sponsoring daily walking tours that will emphasize flowered motifs on the city's historical buildings.
The Philadelphia Museum of Art has opened an exhibit highlighting the artistic portrayal of flowers around the world. A downtown proprietors' group is sponsoring a floral window-decorating contest.
* The flower show is open to the public through Sunday. Tickets are $14.50 each (half price for children under 12).