The Arctic-style winters of the northern United States (Hardiness Zones 3-5) need not be a reason to deny yourself a beautiful garden. Many favorite perennials have the wonderful ability to hunker down and hibernate during a long, sub-zero winter, then awake for an intense season of growth and bloom. In fact, many plants actually require this cold dormancy as part of their growing cycle. One of the virtues of northern gardening is the almost-assured blanket of snow that acts as a protective mulch against destructive freeze/thaw fluctuations. However, it's best to first put down a thick layer of organic mulch (dry straw or chopped leaves) over dormant perennial beds after the ground has frozen. This assures undisturbed cold storage of plant roots during the winter. Make sure that perennials are not exposed to standing pockets of water and ice; this can kill plants as surely as anything. In summer, high humidity can be a problem in the northern regions; try to provide good air circulation in the garden to discourage mildew and other diseases. The design offered here will give you a lush, colorful garden that maximizes the all-too-brief summer season; some are varieties your southern conterparts can't grow. So there is some justice after all!