The Garden: Under Glass

THE GARDEN

For the millions of mulchers, seeders, weeders, pruners and preeners of U.S. Suburbia and Exurbia, spring arrives in a blaze of nursery catalogues and dreams of floral glory. This month gardening buffs have been streaming through the nation's flower shows, green thumbs twitching. All winter, in fact, a surprising number of them had potting soil under their fingernails. For greenhouses are getting to be almost common-or-garden.

Rich men have had them for centuries; Tiberius Caesar raised cucumbers in a mica-covered "forcing house" when his doctor advised him to eat warm-weather vegetables the year round. But today more and more families...