There are gardeners, and then there are plantspeople. The former include, to judge from the statistics, most of us--folks who've jumped on a national outdoor-hobby bandwagon in the past decade or so. We're the planters of marigolds, the clippers of spirea, the nurturers of Colorado blue spruce; we might experiment with a variegated maple, a tufted hairgrass, but that's about as good as it gets. Plantspeople, on the other hand, study catalogs. And Web sites. And coffee-table books on English castles and Japanese temples. They drool over "Hakuro Nishiki" willow, its clouds of pink-and-white leaves evoking a cherry tree in bloom; over fir "Horstmanns Silberlocke," its white-bellied needles curled upward to suggest a frosting of snow in July. And when they can't stand it anymore, they call Green Value owner Richard Swanson; he travels the nation to locate suppliers, check cold-hardiness, and arrange shipping to a ten-acre lot off I-35 where--here's the best part--he sells the aristocratic flora at entirely proletarian prices. Thus do gardeners become plantspeople.