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How to Build—and Maintain—the Perfect Window Box

Expert tips and tricks for making the most of your garden, no matter how small.

Photograph by Jeff Elkins

Ample garden space can be as hard to come by in DC and its close-in suburbs as a free parking spot. An alternative? Window flower boxes, which can be seasonally adjusted or planted with hardy perennials for year-round verdure. Tom Hammond of Ginkgo Gardens on Capitol Hill walked us through a step-by-step guide to building and maintaining them.

1. “You can really use anything for a flower box,” says Hammond, but it’s “crucial there are holes in the bottom” for drainage. Otherwise, you’ll have a swamp.

2. Cover the drainage holes with coffee filters. This keeps the water flowing but stops soil from falling out. Contrary to common belief, gravel isn’t necessary.

3. Use potting soil, not top or garden soil. “And definitely don’t dig up dirt from your yard.” You don’t need to replace the soil each year—a bit of compost will re-enrich it.

4. If you didn’t use a slow-release fertilizer, invest in some Miracle-Gro Bloom Booster. Simply mix the powder with water and sprinkle it over the soil.

5. Evaluate the sunlight/shade situation for the windows where you’ll be hanging boxes. “Your plant choices depend entirely on how much light reaches them throughout the day,” Hammond says.

6. Hammond uses the thriller/filler/spiller method for choosing plants, meaning he picks one tall, eye-catching plant; another that provides good cover over the soil; and a third that overflows down the sides of the box.

7. “Ignore the advice on the tags about spacing the plants,” he says. You’ll want them to fit in tightly, “and that’s perfectly okay.”

8. Place the plants in the flower box and then use a cup to sprinkle more soil around the base of each. “A layer of mulch on top will keep out weeds and retain moisture,” but leave about an inch of room around the lip of the box for rainwater.

9. To keep plants happy, “stick your finger about an inch into the soil—it should be damp.” If not, mimic a light rainfall with your hose’s “shower” setting.

This article appears in our June 2016 issue of Washingtonian.

Design & Style Editor

Hillary writes about interiors, real estate, arts, and culture. She is the former digital media editor of The New Republic, and her work has also been published in Glamour, The New York Times Book Review, and The Washington Post, among others. You can follow her on Instagram @hillarylouisekelly or on Pinterest @hlkelly.