Sprucing up a facade is just the start of the window box's talents. Its potted plantings also bring garden scenes up close and invite flowery perfumes indoors. And because window boxes are so prominently placed—and generally on public view—they claim more attention than patio pots without requiring any additional effort or expense. They're amazingly versatile, especially if you push past a mere gathering of geraniums, as pretty as those can be, for a layered mix with nuance and dimension.
Like any garden planting, a window box comes with its own set of design considerations. Its close tie to the house is one. Study your home's exterior to see which windows need dressing up and what cues the architecture provides. Traditional houses, especially, welcome window-box plantings, which play up elements such as shutters and handsome trim.
But look from the inside out, too. Consider which rooms you use often enough to warrant flower-edged views, and give thought to plant size and placement, as these window plantings can also be a chance to add privacy. Dwarf conifers, for instance, can block unwanted views year-round, while grasses are perfect for light screening. For boxes below casement windows, tuck in low growers that won't mind being brushed over; for lofty second-story boxes, show off graceful spillers that cascade dramatically.
Shown: This box has it all. Wispy gaura improves the view indoors and out; golden creeping Jenny adds cascades of foliage; and salvia, 'Phantom' petunias, and 'Diamond Frost' euphorbia fill in the lush display.