By Julia Lowndes

Despite what the name might imply, window boxes are anything but confining. They can be a great way to test the limits of a container garden and to experiment with new plants, while adorning your home with one-of-a-kind designs.

Ready to give your home and the environment a boost?

Set up your space

Every window is worthy of beautification, whether with a small box in the shade or a large display in full sun. Each location comes with different requirements to consider. According to Leah Blanton, PHS Public Landscapes Project Specialist, it’s essential to assess your box, climate, and soil before starting your design. “The box will depend on your window dimensions and aesthetic,” she says.

When it comes to location, not all boxes are created equal. A box’s material can be well suited to some climates or detrimental to its longevity in others. For example, a rainy area is better off with fiberglass or vinyl boxes than wood boxes, which are prone to rot. Gardeners in cold climates should avoid terracotta boxes and opt for more durable metal boxes. Not all boxes come with drainage holes, so drill them on the bottom to give excess water an exit route.

“I always put either gravel or broken clay pots in the bottom of the box to ensure proper drainage,” says Calvin Phun, (right) a Philadelphian whose distinctive window display won a blue ribbon in the 2018 PHS Gardening Contest. 

Once you’ve chosen the proper material, the next decision is size. Picking a box that’s a few inches smaller than the width of your window is the rule of thumb, but feel free to mix it up to your liking.

For the last step, reach for a bag of potting mix rather than potting soil. The organic materials in potting mix retain moisture better than soil, meaning your window boxes can handle a few days alone while you’re out of town. 

Choose a theme

You have your box and soil; now it’s time to pick a theme. It might seem intimidating, but it’s also an opportunity to explore your creativity. “There are endless combinations, but the way I begin is to come up with a style or theme,” says Leah. “That could be inspired by a style of gardening, color-driven, or texture and form-focused -- you can think about all of these in an arrangement.”

Leah recommends sticking to a color palette and adding surprising variations in textures and height for visually pleasing contrasts. Have you noticed how the round, cascading leaves of a Creeping Jenny highlight the sharp edges of a coleus?

Inspiration for themes is everywhere, from your neighbors’ front yard to the allure of untamed nature. “When traveling to Phoenix, I was inspired by the desert and all of the awesome beauty it holds. The cacti, succulents, flowers and other plant life that thrive in such difficult terrain was so inspirational,” says Calvin. “I brought back a lot of that and incorporated it into some of my latest creations.”

No matter where you find inspiration, Calvin believes that the best window boxes are nurtured by a passion for horticulture and design.

“Whatever [your theme] is, you have to be prepared to inspire both yourself and those who will see it as they pass by your home. Just be committed.”

Select your plants

As in any other garden, it’s crucial to choose plants that will receive proper sunlight. Blooming annuals thrive in boxes that receive direct sunlight, while foliage plants like hostas bring texture and depth to shady boxes. Try mixing impatiens and sweet potato vines at a shady window; the contrast is appealing and versatile.

“In a window box planting, I’d stick to plants that stay compact so you have more space,” says Leah. “For sun I’d recommend a mix of perennials and annuals, like perennial Allium 'Millenium,’ annual Agastache species like the ‘Kudos’ series, an annual Phormium for height, and a trailer like ivy or Tradescantia sillamontana.”

In shady areas, she recommends colorful coral bells, the wide leaves of Solomon’s seal, and lush Oxalis ‘Charmed Wine’.

When choosing his plants, Calvin seeks combinations that generate an emotional response. He likes to experiment with new plants that challenge him and beautify his surroundings. “When I walk outside my building, do I get a sense of pride from what I have contributed to my neighborhood? Does it give joy to people walking by? Introducing different types of plants always draws attention and a response,” he says.

For a fresh and practical twist to the classic box, bring some herbs into the mix. Besides being useful in the kitchen, herbs can elevate a window box.

“If you want to incorporate herbs, choose ones that offer something else to the planting. For example, purple basil, lavender for its texture and fragrance, and fennel or dill for the ornamental seed heads,” Leah says.

Make it sustainable

Window boxes are an easy way to show the earth some love without digging up your backyard. Pollinators are always looking for new gardens to visit, so Leah recommends incorporating native perennials into window boxes to attract these beneficial creatures. Some of her favorites include allium ‘Summer Beauty,’ butterfly weed, and agastache species. 

Try setting up a pit stop for birds, frogs and toads. A small feeder or bird house adds dimension to your window box while creating a habitat for animals that will eat pesky mosquitoes and other insects. Avoiding insecticides is a simple way to garden sustainably. 

Another beneficial trait of window boxes is their ability to house repurposed goods. Line plastic water bottles in the bottom of the box to create a light-weight drainage system. Repurposed goods also work as charming decorations to enhance your theme. Old watering cans, small shovels and knickknacks can brighten up your display while clearing out your garden shed.

A note from an award-winning gardener

Calvin got involved with window boxes for a reason. They have a significant impact on the community that is often overlooked.

“When you walk down any street and see a lot of homes with window boxes that are full of beautiful creations, you really do get a sense of a neighborhood, of community, of pride,” he says.