Photography by Ben-Schonewille / iStock / Getty Images Plus
Consider the Architecture
Although window boxes enhance the curb appeal of any home, they are particularly striking when used on small-scale cottages with shutters, half-timber, half-stone farmhouses, and traditional homes with a center front porch. “South-facing homes are ideally situated, because they provide six hours of full sun each day,” says Rhonda Shoemaker, owner of St. Louis–based Glorious Gardens, “but window boxes also work on southwest- and southeast-facing façades, which receive four hours of sunlight.”
Photography by Alise O'Brien
Cindy Cramer designs window boxes for her home with stunning results.
Choose the Right Container
Window boxes are sold in a range of materials, so what should homeowners consider when shopping for them? “There are a lot of great composite materials made of plastic that look like metal or terra cotta,” Shoemaker explains. “Just make sure they have drainage holes or that you’re able to drill holes in the bottom.” Shoemaker also suggests avoiding terra cotta, clay, and ceramic containers. When soil freezes, it contracts and expands and could cause containers to break during the thawing process. For those who prefer the look of wooden window boxes, just be sure to insert a metal liner to prevent wet soil from rotting the container. University City resident Cindy Cramer purchased copper boxes and had them sealed to keep them from taking on a patina. “After three years, they still have that beautiful bright copper color,” she reports.
Soil Does Matter
Using a good potting mix is key. Avoid heavy clay soil from the ground, says Shoemaker: “Water can’t drain through it, and your plants will drown.” Instead, choose a potting mix that’s already blended with slow-release fertilizer to decrease the amount of maintenance required. Soil-less peat-based planting mix is another option. “Use a liquid fertilizer about once a week to promote bloom and bud growth,” says Shoemaker.
Plant Palette
Choose flowers that repeat-bloom and create a strong floral presence, such as geraniums, pelargoniums, and lantana. For a “wispy effect like baby’s breath,” Shoemaker likes euphorbia Diamond Frost. “It’s like a little cloud sitting around your planter.” Cramer favors SunPatiens and begonias. “They tolerate the sun, are easy to grow,” she says. Don’t forget to include colorful, textural trailing plants such as coleus or dichondra, and plants that create height, like silvery, striking Persian shield. Fragrant heliotrope draws pollinators. “If you want to start with seeds, plant edibles such as herbs, vining cherries, or small ornamental peppers,” Shoemaker recommends.
Courtesy of Glorious Gardens
Design Planning
Determine what you want your window box to look like in advance, and consider a repeating pattern of flowers and colors to impart a unified look. Add soil up to 1 to 2 inches below the upper lip of the box. Follow the “thriller, filler, spiller” rule, which Shoemaker calls a great novice device: “The thriller is a strong vertical element, the horizontal filler is usually positioned in the middle of the box, and a cascading spiller leads your eye up to the box and softens the overall effect.” Tall items look best when they’re positioned in the middle back.
Don’t Forget Maintenance
Watering should be done about every other day. To simplify care, Cramer’s husband, Jeff Cramer, built a drip irrigation system with tubing that “snakes up the house and into each window box so that all we have to do is turn on the water in the morning for 2 or 3 minutes,” she says. Water the soil, not the foliage, because water droplets magnify the sun, resulting in burns to the leaves. Removing spent blooms is also important; this redirects energy for plants to create more blossoms. Pruning is necessary, though somewhat subjective. “Plants grow at different rates, so prune back those that tend to take over, giving other plants more sunlight and space,” says Shoemaker.
Final Words of Wisdom
At the end of the growing season, empty out the boxes and install winter décor such as evergreen boughs, berries, or river birch logs. Cramer sets pots of burgundy mums in her boxes until they’re spent: “I love extending the season.”
