Even the most accomplished container gardeners are impressed when they encounter a full, lush, well-designed window box. Why? Because anyone who has planted and cared for one knows that a window box presents certain challenges. First, there's that odd shape to deal with. Usually long and narrow, window boxes seem to inhibit even the most daring designers, who inevitably fall back on a row of geraniums or a few cell packs of pansies. Maintenance is another issue: watering without spattering the house, the windows or passersby; deadheading and managing to keep the show going despite a small growing area. These are all hurdles, but surmountable ones.
Before buying any plants—or even the container—decide where your window box will be placed. Keep in mind that those sitting on a window ledge will obscure part of the view, more so as the plants fill out. This is desirable if you're trying to obliterate an offending view, but less so if you want to see beyond the box to the rest of your garden. A box mounted below a window is ideal, but requires non-gardening-related skills such as drilling and measuring (see “Mounting Window Boxes,” on next page). Select a location where watering will not damage nearby surfaces (e.g., not above a dining table or wicker chair).
Choose your container with care
Next, choose your container, keeping proportion in mind. A box sitting atop a window ledge should almost fill its length: too short and it will look skimpy. The same goes for a box hanging below a window. If space allows, it could even extend beyond the width of a window for a more generous look. Naturally, the deeper the container, the more space there is for roots to spread out and for water retention, but larger boxes are typically heavier, too. Before installing, determine how much weight your wall and the hanging brackets will tolerate when the soil is fully saturated. Check the packaging with the hanging brackets; sometimes a maximum weight load is provided. Fill one of the boxes with soil, water it well and lift it (or weigh it on a bathroom scale). Then, estimate if you need more than two brackets, or sturdier ones.
Look for practical materials that suit the style of your house. Those commonly used include plastic, metal and wood, and each has its merits and drawbacks.