Gardens with Cool Summers

Cool summers are a joy for people and plants alike. Some of the advantages of gardening in northern latitudes or at higher elevations in mountainous regions include low humidity and delightfully cool summer days that seldom exceed 80° F (27° C). Additionally, many coastal areas benefit from cooling lake or ocean breezes.

In these locales, if you have a sunny garden site and you crave a sumptuous traditional flower garden, you're in luck. Color balance is a crucial factor of garden design, and many people quickly discover that they have favorite colors when it comes to foliage and flowers. In sunny sites bright, saturated colors usually show up best, whereas white and light pastels are easily lost in the sun's glare.

Towering mauve-flowered foxgloves, deep pink and red hollyhocks, and the huge, fragrant magenta or deep pink flowers of peonies are the pride of sunny gardens in early summer. High summer belongs to colorful annuals, combined with pink phlox, warm-hued daylilies, and lavender-blue catmint. Late-summer color is often even stronger, with the deep blue flowers of monkshood, the golden flowers of rudbeckia, and the vivid pink flowers of turtlehead blooming just ahead of those of bright yellow sneezeweed. In autumn, cool blue and purple asters bring the blue of the sky down to earth and unite it with warm-hued gold and burgundy chrysanthemums and trees ablaze in brilliant seasonal red and gold.

Maximizing Cool Summers

Though temperatures in the cool-summer areas of the country are perfect for summer gardening, because plants are less likely to wilt under the sun's glare and the soil is more likely to retain sufficient moisture for plant roots, the season often seems painfully short. Frosty nights may persist well into spring, delaying planting until summer is nearly under way. Invest in perennials, shrubs, and hardy bulbs. These plants, which are in the ground and ready and waiting for spring are a reassuring presence, making it easier to wait for warm planting weather before setting out summer annuals.

Fortunately, there are a number of cold-tolerant annuals that can be planted before the last frost has passed. Some of these are calendula, dusty miller, lobelia, pansy, snapdragon, and sweet alyssum. Yet because bedding plants are often grown in heated greenhouses, they fare best in the garden when they become accustomed to outdoor conditions gradually, over a period of 2 weeks. This process, called hardening off, initially involves setting potted plants outdoors in a sunny, protected spot for a few hours each day for a week. Then, the week prior to planting, allow them modest exposure to chilly winds and cool nights, but bring them indoors if hard freezes threaten. By this rime, their stems will have become sturdy and new leaves will be a bit thicker and more frost-tolerant. The move into cold soil and chilly air will only cause a modest shock to the plants' roots.

Raised Beds and Berms

Sometimes plants in cold-winter climates are ready to go into the garden in spring, but the soil remains too clammy and wet for planting. So gardeners face frustrating delays. Building raised beds or berms may give you a head start on the planting season, because they warm up and dry out faster than lower-lying garden areas. Raising the soil level even a few inches can offer the additional advantage of superior drainage for plant roots. Indeed, the combination of great drainage and cool-summer weather brings out the best in several stellar perennials, such as artemisia, catmint, and veronica, which require excellent drainage to reach their full care-free potential.

Coping with Winter Cold

Though cool summers are splendid, winters in northern latitudes and high altitudes are often long and cold, so plants grown there must have exceptional hardiness. Use the hardiness ratings for your locale as a guide when shopping for plants. Also look for protected areas in your yard, called microclimates. Microclimates exist in spaces protected from freezing winds by walls, fences, or dense evergreen planting, and also are places where a masonry wall or rock outcropping may absorb and hold the sun's heat, elevating the surrounding temperatures. You can use these warm spots to grow plants rated one or two Zones warmer than your area's Zone.

To help garden plants get through freezing winters, use mulches. The insulation provided by a generous layer of mulch placed over the root zones will protect perennials and shrubs from cycles of soil freezing and thawing, which can heave the plants out of the ground, leaving the roots exposed and vulnerable to freezing and dehydration. Mulching is especially helpful in mild-winter areas where there is no consistent snow cover. The best winter mulches are fluffy organic ones like leaves, hay, straw, and evergreen boughs. If you use leaves chop them with a shredder or lawn mower. The chopped leaves will offer good insulation and are less likely to blow around.