Types of Hardy Perennials

• Herbaceous perennials die back each year, returning each spring from their roots. These perennials generally do better than woody perennials because they store energy in their roots during the growing season so they can send up fresh shoots in spring. Spring and summer bulbs also store energy for the following year and require a prolonged chill time in winter. If a plant is known to be a difficult grower in the South, it should be well suited for the extreme North.
  
  

Herbaceous Perennials

• For spring color, look for cornflower (Centaurea montana), pinks (Dianthus spp.) and Virginia bluebells. Primroses, growing in poor, rocky soil, can actually poke through retreating snow. Summer perennials include hardy geraniums, bellflower (Campanula spp.), bleeding heart and Artemisia. Zone 3 gardeners can grow showy Delphiniums and lupines that will make southern gardeners drool. Late summer and early fall bloomers include the white, pink or purple monkshood, Culver's root (Veronicastrum spp.) and Phlox paniculata.
  
  

Bulbs

• Most spring and summer bulbs requiring a winter chill are good candidates for the cold garden. Most tulips and hyacinths, infamous for being temperamental in the South, do well way up North. Daffodils, perhaps the most versatile spring bulb, are a great choice, as is crocus, which pushes its way through the snow in early spring. Peony is also reliable. It thrives with the winter chill and mild summer temperatures. For summer bulbs, try the spiky-flowered gayfeather (Liatrus) and classy Asiatic lilies.
  
  

Tips

• To fill in color gaps left by fading perennials, plant cool-season annuals. Try stock, bachelor's button, lobelia and impatiens. Pansies and Johnny-jump-ups can fill spaces throughout the season in a cold climate. A mulch of shredded leaves or evergreen boughs provides winter cover when snow is scarce. If a predicted early freeze threatens tender blooms, polyester row covers or flannel sheets protect them through the night. Remove the covers the next morning.