Window Box Gardening: A Complete Guide to Charming Displays

Nothing says quaint charm like a window box brimming with flowers. I loved them for years but hesitated—intimidated by installation and afraid of mistakes. But for any homeowner with basic DIY skills, it’s a great weekend project; for others, a carpenter can install boxes in a snap, leaving the fun part—planting—to you.

Materials

Window boxes come in wood, metal, ironwork, or plastic—ready-made or custom—to match or contrast your window trim. Some plastic boxes can be painted any color, giving a wooden look with plastic durability.

Find them at nurseries, garden centers, home improvement stores, hardware stores, and online custom builders. Hiring a carpenter for custom boxes removes DIY anxiety.

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Murphy & Co. Design

Location

Obviously under windows—but not every window. View your house from the street. Choose feature windows: flanking the entry, or a row by the living room. Second-story boxes are dramatic but ensure the window opens for watering and maintenance access.

Elaine M. Johnson

Drainage

Most boxes have drainage holes with trays. Openwork iron or metal boxes often use cocoa liners that drain too freely, leaving plants thirsty. Fix this by lining cocoa liners with perforated plastic (trash bags cut to fit with holes poked in them).

Wooden boxes can be painted inside with waterproof roofing cement to slow rot. Still drill drainage holes, but this extends box life.

Chris Kauffman

Plant Selection

Many small flowering plants suit window boxes. Exploit the elevation with trailers—ivies, petunias, lobelias, impatiens, sweet potato vines—but balance with vertical elements: geraniums, marigolds, tiny evergreen topiaries, low ornamental grasses, even miniature roses. Keep plants under one-third the window height to avoid an overgrown look.

Iron Accents

Installation

Many boxes use L-brackets attached to wood studs under the sill. For brick or stucco, use a masonry drill bit. Once brackets are secure, set the box and fasten with deck screws.

Center ready-made boxes beneath the window. Width should match the window plus trim, or window plus 4–6 inches if shutters exist. Undersized boxes look out of proportion. Standard depth is about 8 inches; custom depths should stay proportional.

Planting Tips

Install boxes before planting—they’re too heavy to move once filled. Use quality potting soil or bagged garden soil, plus slow-release fertilizer. For cacti or succulents, use a specialized fast-draining mix.

Pack plants densely, especially annuals—they only last one season. Six-packs, 4-inch pots, or 1-gallon containers work best; larger sizes overwhelm the box.

Michelle Jacoby, Changing Spaces

Watering and Fertilizing

Watering frequency depends on plants (thirsty impatiens need daily; succulents less) and sun exposure. More sun = faster drying. Most window boxes need water several times a week. Use a hose-end sprinkler for low boxes, watering cans for upper stories, drip irrigation for any level. Self-watering boxes store water for up to two weeks—great for busy gardeners or vacations.

Fertilize according to plant needs; water-soluble fertilizer once or twice a month is a good general rule for lush growth and bloom.

The Windowbox Gardener

Style

Window boxes suit cottage style naturally, but material and plant choices can create elegant, formal, sleek, or contemporary looks. Painted wood with colorful annuals reads casual; black ironwork with evergreens and white flowers feels formal. Neutral wood with identical low grasses or small cacti reads contemporary. Let your home’s style guide your choices.

Next: See how to make a basic window box