A window box filled with flowers or colorful foliage connects a garden to the house. It adds character and enhances the views from indoors and out. When I see window boxes, my first impression is that the house must be really cozy inside. This article looks at how to choose and plant window boxes to dress up your home’s curb appeal throughout the year. In other words, Window boxes that wow!

Our house features a 9-foot-long cedar window box outside our kitchen. The box faces north and gets limited sunlight until the afternoon. That doesn’t stop me from creating a four-season shuffle of good-looking plants that we enjoy seeing from our kitchen table and from the front sidewalk.

In the spring, there’s colorful red and green leaf lettuce and spinach, which I sow from seed and harvest through early June. Once these shade-loving, cool-season greens start to flower, I replace them with begonias, caladiums, asparagus fern, oxalis, vines and fuchsia, which attracts hummingbirds. In fall, my window box wears an assortment of ornamental peppers, kale, cabbage, asters and miniature pumpkins. And in winter, it’s filled with spruce branches, dried hydrangea flowers, red-twig dogwood stems and pinecones. The best part?  There’s no bending over or kneeling when it comes time to plant.

Photo by Nina Koziol

Up and Away

Window boxes are like any other containers. They need drainage holes, lightweight soil-less potting mix, fertilizer and consistent moisture. Garden soil is far too heavy for most containers, especially those that are attached to a building. And, when you water them, consider that one gallon weighs a little more than eight pounds. Add in the plants, and that’s why lightweight soil-less mixes are a good idea.

A Window to the Past

Gardeners have enjoyed window boxes since the Victorian era. Ready-to-build kit houses, such as those sold by Sears, often featured the window boxes already attached to the exterior walls when the kits arrived. In the 1920s, popular architectural plans for Cape Cod-style houses, Tudors, Dutch Colonials, bungalows, Arts and Crafts-style houses and many others featured window boxes overflowing with flowers. It was a clever marketing tool to attract buyers who saw the homes as charming and inviting.

More than a century ago, architect Gustav Stickley wrote about one of his bungalow designs, stating, “These flower-boxes at the sunroom windows bring the garden and house into such intimate companionship that one hardly knows where one leaves off and the other begins.”

Many of Chicago’s brick bungalows, built in the 1920’s, had brackets and window boxes made of concrete to match the windowsills. The concrete boxes had decorative scrolls, but many are long gone having cracked and crumbled in the last century.

Photo by Nina Koziol

Window Box Materials

You can buy window boxes made from wood (rot-resistant cedar), vinyl, plastic, stone, and metal. Some window boxes have built-in water reservoirs. The choice, style and color of the box should be in keeping with the architectural style of your house. If resources allow, buy well-constructed window boxes that will be long-lasting and won’t chip or split where winter temperatures are extreme.

Unlike metal, wood and other materials stay cooler, a consideration if the box faces south or west. Wood will require staining or painting every few years. In cold climates, thin plastic window boxes may crack.

Choose sturdy brackets that can be anchored to the house.To prevent the box from falling off the brackets, you may need to secure the box directly to the house as well. If you plan to paint the box, look at the color of your house, the front door, window sash and trim for ideas. Or, pick an accent color. Paint suppliers, such as Rustoleum, offer paints for wood, metal and plastic in a wide range of colors. Some artistic gardeners stencil designs on the front and sides of the box.

Size Matters

As a general rule, the box should be about the same width as the window. Deeper boxes are better than inexpensive shallow types. Not only will a shallow window box need watering more often, it may look rather puny.

Before you buy, take a large piece of cardboard or poster board and cut out a few sizes and tape them under your windows. Step back to the front walk or side yard and see how they look.

Window-box liners made from plastic or metal can protect the exterior box. They’re available at garden centers, big-box stores and online. Liners protect wood from wet potting mix, which can cause wood to deteriorate over time.

When you attach the box, leave a little space between it and the exterior wall so that water may drain away from the house. You don’t want to drain water onto the wall below or trap moisture behind the box. In our window box, we drilled holes under the front-facing panel of the box so that the water drains a foot away from the exterior wall.

Photo by Nina Koziol

Choosing Plants

Which way does your window face?  If it faces east, the box will typically receive morning light. North-facing boxes get little light until the afternoon, if the sun is not blocked by trees or buildings. In these situations, I like to use shade-loving annuals with good-looking foliage. Caladium, coleus, sweet potato vines, and some tropical house plants do well in this limited light. Canary Wing begonia with its chartreuse leaves and orange flowers does very well in our north-facing window box and adds a ton of color in the shade.

South and western exposures mean bright sunlight (and probably more watering, especially during hot summer weather). For these situations, I use flowering annuals like petunias, compact zinnias, ageratum, angelonia, lantana, salvia, sedum, calibrachoa and sun-loving coleus. Herbs are another choice for a window box in sun. Basil, fennel, cilantro, parsley, rosemary, thyme and oregano add color, texture, and fragrance when you brush the leaves.

Before you plant, fill the box about half-way with moistened potting mix. Take the individual plants out of their pots and set them on the mix. I like to place plants a few inches apart for an instant impact. Add more moistened mix around the roots but leave some space at the top of the box so the potting mix won’t spill over the edge when you water.

Maintenance

Caring for your window box plantings is like taking care of plants in the ground. The plants need water, especially if rain doesn’t reach the potting mix. About every week, I use a water-soluble fertilizer to keep the flowers coming. If needed, I’ll pinch off the spent flowers to encourage more blooms.

When it comes time to change the plants for fall, I remove the old ones, rootball and all, and compost them. I add some granular fertilizer and mix it in with more soil-less potting mix. Next, I set the plants on top and add more potting mix around them. Freshening that window box scheme allows me to celebrate the changing seasons.

A Window Box for Every Garden

Window boxes can definitely dress most, but not all homes. For example, a ranch or a mid-century modern house may have walls of windows that call for more contemporary containers around a doorway rather than a window. Don’t have the right windows for a box?  No problem. You can plant and place a long window box on a patio, by a walkway, along a driveway, on top of a retaining wall, or on the floor or rails of a deck or porch. Then sit back and enjoy the compliments from passersby.

Photo by Nina Koziol