Window box planters are an affordable outlet to experiment with your creativity. And although there's a lot of creative freedom with planting window boxes, there's also a right way to do it. This popular garden element is the perfect opportunity to show off the wide range of possibilities a few feet of soil can offer, so learn how to plant window boxes with this guide.

How to Plant Window Boxes

The first step in planting a flower box is choosing your box and where to hang it. Don't underestimate how heavy a window box can be—it's filled with soil and plants and gets even heavier when watered. We recommend buying a sturdy box made of hardwood like redwood or cedar rather than pine (which rots quickly) and securing the box with a window box bracket.

Always make sure your window box has drainage holes. To aid drainage, place 2 inches of nonbiodegradable packing peanuts or old wine corks in the bottom of the box, and then cover with landscape fabric to prevent soil from seeping out.

Next, fill the box halfway with potting soil, and add your plants. Make sure your plants are placed a few inches apart to give them room to fill out. If you want immediate impact, you can plant closer, but know that you will need to pinch or prune your plants to prevent overcrowding. Once your plants are in place, fill in the gaps with more soil and lightly pat down around the plants.

As with all container plantings, choose plants with similar water and light needs, and expect to water them more often than those in the ground. Water thoroughly once the soil has dried out.

What to Plant in Window Boxes

Most successful window boxes contain a mix of these three primary plant types. These are some of our favorites in each category.

Thrillers

These are your hero plants—the ones that command attention and drive the rest of the design.

• 'Katrina' African iris: Tropical flowers top long, spiked leaves.
• 'Sallyfun Deep Ocean' salvia: Fragrant and a butterfly magnet.
• 'Frydek' alocasia: Big, emerald green leaves anchor a tropical look.
• 'Kong Red' coleus: Massive, upright leaves; prefers shade.

Spillers

Trailing over the side of the container, these plants add softness and a little romance.

• 'Neon' pothos: Chartreuse leaves are like rays of sunshine.
• 'Blanket White' petunia: Fast grower with cottage charm.
• 'Angelina' sedum: Foolproof plant with fleshy yellow leaves.
• 'Ivy League Deep Pink' geranium: Flowers spring through summer.

Fillers

Midsize plants bridge the space between thrillers and spillers.

• 'Aaron' caladium: White-center leaves look bright and fresh.
• 'Pink Splash' polka dot plant: Foliage as impactful as any flower.
• 'Mango Tango' agastache: Peach-color flowers go with everything.
• 'Impreza Violet' impatiens: Tidy mounds of long-blooming flowers.

5 Window Box Design Tips

Keep in mind a few basic design principles, then unleash your creativity.

1. Use Repetition in Your Planting

Repetition is foolproof for how to plant window boxes with a cohesive look. This 15-foot-long box is planted with repeating groups of ivy ball topiary, chartreuse coleus, and white caladium for a sense of flow and order.

2. Choose a Focal Point

Choosing the centerpiece first means the rest of your plant picks will fall into place. This design started with a lemon cypress topiary. Coleus bridges the colors of the foliage and the brick, and creeping wire vine loosens the design.

3. Think About Texture

This arrangement achieves masses of texture by mixing wispy purple fountain grass, croton, and spilling sweet potato vine. The form differences ensure each plant stands out despite the tightly packed box.

4. Take Cues from the Landscape

For this garden door container, red-orange copperleaf and variegated sea hibiscus tie into the color of a nearby Japanese maple. It's filled it out with English ivy, which also grows in the backyard, plus Spanish moss.

5. Stay Consistent

Try choosing a single color palette for all plantings around your house. This window box planting uses green and white, with hints of yellow. If your window box hangs near an outdoor dining table, tuck in fragrant herbs like thyme, oregano, and mint as fillers.

How to Plant Window Boxes with Confidence

As long as you remember to include a thriller, spiller, and filler that all have the same light requirements, you can assemble a full, colorful window box. Keep garden design elements in mind on a smaller scale, and give your box plenty of water to keep the plants happy all summer long.