Window box renaissance

Sunset, May, 1996 by Steven R. Lorton

When asked his opinion of window boxes, the late, great landscape architect Thomas Church reportedly offered this terse verdict: "Remove them." Though Church evidently considered window boxes declasse, these days many Western gardeners obviously disagree. In fact, a window-box renaissance is blooming. We've been watching this growing phenomenon, and for nearly a year we've ben collecting evidence submitted by home gardeners and professional horticulturists from around the West. Scores of Sunset readers - from Alaska to Arizona have shared their secrets of success and sent us photos of their boxes. On these pages, we're pleased to pass along some of their collective window-box wisdom.

THE BOX

Window boxes are simply containers, albeit longer and skinnier than most. Remember that the bigger the box, the heavier it is, but also the more room it provides for roots to spread.

Most garden and home supply stores stock ready-made boxes in a variety of shapes and sizes.

Good materials for building your own box include cedar, redwood, and pressure-treated lumber; painting or staining the wood will prolong its life. You can plant directly in the box or use plastic or metal liners. Plastic liners are sold commercially, and metal liners can be custom-fabricated inexpensively by many metal shops. All boxes (and liners) need drain holes: a 1/2- to 3/4-inch hole for each foot of box will suffice.

Window boxes should be supported from the bottom. Decorative wooden braces, sturdy metal shelf braces, large angle irons screwed into the wall, and custom-made steel or iron brackets all work well as supports.

The box should also be securely anchored to the wall behind it so that it won't lean forward and topple off the supports. But do not attach the box directly to a wooden wall or you'll encourage the siding to rot. Instead, cut a pressure-treated 2-by-2 or 2-by-4 into a piece slightly shorter than the length of the box, and bolt it horizontally to the wall. Then screw the back of the box to the horizontal runner. This allows plenty of clearance for drainage and air circulation between the box and the wall.

THE SOIL MIX

Commercial potting soil mixes work best. Most of these are lightweight but retain moisture well. Some gardeners like to mix well-aged manure into potting soil (a good recipe is 1 part manure to 3 parts potting mix, although it can be mixed 1 to 1).

To be sure plants get the nutrients they need, you can work a controlled-release fertilizer into the soil mix at planting time or make monthly applications of a complete liquid fertilizer (12-12-12, for example).

In most cases, soil needs to be replaced only once a year. If your box is empty in the winter, remove the soil and give the wood a chance to dry out. Many gardeners fill empty boxes with cut evergreens for winter display.

THE PLANTS

In May, nurseries and garden centers are well stocked with candidate plants in sixpacks and 4-inch pots. Begonias, fuchsias, geraniums, impatiens, lobelia, marigolds, petunias, and dusty miller are among the classic summer choices for window boxes.

A typical window-box planting consists of three parts: background (tall plants such as geraniums), foreground (low-growing plants like dwarf marigolds), and trailers to spill out of the box (verbena and various ivies).

If you live in one of the West's mild coastal climates, you may want to change plantings three times a year: annuals for summer; cyclamen, pansies, and ornamental cabbages and kales for winter; and primroses or bulbs for spring.

Since window boxes are often exposed to full sun, drying winds, and the reflected heat of the house, it's crucial to water at least daily, and perhaps even twice a day in the hottest weather (drip-irrigation tubing can save you a lot of effort). Pinching off faded blooms helps keep flowers coming.