HORTICULTURE IS HOT.(market, survey data on gardening)(Brief Article)(Statistical Data Included)

Byline: Peter Francese

With Martha Stewart's launch of her own branded gardening collection, there can be little doubt: the plant business is flourishing. Gardening has become the second most popular leisure activity in the country - second to walking - according to New York-based Scarborough Research. In fact, the National Gardening Association (NGA) reports that most American households (80 percent) tended to plants last year, up from 64 percent in 1996.

The purchase of indoor and outdoor plants represents a thriving market - one that is poised to grow eve