How dry it is! Understanding the summer climate west of the Cascades baffles lots of residents. The “emerald green” attitude extends to believing that summer months wrap themselves in rain and mist just as winter does. However, our “modified Mediterranean” climate makes water planning as important in Seattle as it is in Spokane.
Summer of 2002 brought only 4.6 inches of rain at Sea-Tac (May 1 through November 1). September and October, usually good planting months, totaled only 1.08 inches combined. Another way to get perspective on this summer rainfall total-just imagine you’ve planted hybrid rhododendrons in April. They require about an inch per week, ideally consuming about 24 inches from May through October. Since less than five inches fell, the rhododendron needs about 20 extra inches from irrigation. Summer often brings gray, rainless days that reduce moisture loss, but don’t add water. Often a shower may just wet the grass and dampen all the cushions on outdoor furniture. Soil under tree and shrub canopies-and deep into root areas-remains dry.
Gardens-and gardeners-need sensible plant choices that will manage summer dryness without needing much irrigation. With water costs going up and a growing population that just keeps demanding more, it’s comforting to grow plants suited to water realities. Local demonstrations, such as the Waterwise Garden at the Bellevue Botanical Garden, educate by showing what works best.
Grouping thirsty plants saves effort and water. Soaker hoses tucked around rhododendrons and roses dribble water to roots without wasting it. (A sprinkler system swishing water into the air may lose nearly 50 percent to evaporation.) Good soil preparation helps to retain applied water.
Champion plants for dry summers include a number of broadleaf evergreen shrubs not hardy in eastern Washington. One of the most beautiful is the “strawberry tree,” Arbutus unedo. This shrubby tree, growing very slowly to about 25 feet, is related to the native madrona and has the same beautiful russet bark color. Place it in a sunny area. Leaves are shiny deep green, and the fall flowers dangle in white pendants. The tree is named for its fruit, globes of strawberry red-edible, but not particularly tasty. The flowers and fruit occur at the same time, generally in November and December, giving the garden welcome late fall color.
If you like a feathery, open plant, consider Nandina domestica, called “heavenly bamboo,” though not related to the common bamboo. Nandina is available in several different cultivar sizes, from small, low growers that almost make a ground cover (Nandina domestica “Compacta”) to six-footers in the standard plant, Nandina domestica. Nandina is beautiful all year round, with pinkish spring growth that becomes green as it matures. Foliage looks bronze in winter. Legend says that in Oriental households, a nandina beside the front door served to listen to the worries of the head of the household. So if you don’t mind speaking to plants, this one might work! Nandina will grow in both sun and shade but has brighter leaf color in sun. Some cultivars may survive icy winters down to 10 degrees below zero, but it’s most often seen in mild Japanese-influenced gardens.
Another good small shrub is hebe, available in many different cultivars. I grow the standard Hebe buxifolia, a tidy three-foot shrub with tight-packed, deep-green leaves. Hebes are native to Australia and New Zealand but are perfectly adapted to the maritime Northwest. All hebes like sun. Some of the cultivars, such as “Patty’s Purple,” can expire in sudden winter freezes.
Of all the summer favorites, I appreciate hardy fuchsias the most for their glorious color. These are cousins, or perhaps brothers and sisters, of the basket fuchsias, but they do well all year outdoors planted as garden shrubs. Some like damp soils, but the common Fuchsia magellanica, with long, four-foot wands draped in dangling red and purple flowers, tolerates low summer water. These are beautiful this year after our mild winter, because long, graceful stems continue to persist through winter.
These agreeable plants contribute gracefully to the look and feel of the water-sensible summer garden west of the Cascades.