The 17 Best Flowers That Will Thrive In Window Boxes

Window boxes are containers that are usually oblong in shape and attached below windows on the outside. They're often made of wood but can be made of many different materials. I have clients who use oblong wire baskets with coir liners as window boxes, which is an easy option. I also have clients with older wooden window boxes, and they usually line the planters with plastic to protect the wood, with holes poked in for drainage. These versatile planters can be used anywhere but are especially charming in a window — usually attached using hardware or wire frames. We've gathered up some ideas for the best low-maintenance flowers that will thrive in them.

One tricky part of caring for window boxes is access. Some of them may be located too high for easy reach for planting and watering, but if they're on a second floor or higher, you will usually access them from inside. Some flowers will increase in size, so don't crowd them in too tightly. Use well-draining potting mix in your window boxes in case a rainstorm comes around. Planting flowers that have a trailing habit and that bloom continually are the best fit for these planters, and that includes many lovely annuals. With regular watering and some occasional deadheading, the flowering plants in window boxes can bloom for many weeks in summer and into fall. The simple "thriller, filler, spiller" design formula (using flowers that fill in space and vary in height) works great for window boxes, but they also look wonderful with an assortment of trailing flowers or even just one variety of flower.

Petunias are an excellent choice for window boxes because most varieties of petunia have a semi-trailing habit, allowing the flowers to drape over the sides of the box as well as bloom upright. With so many gorgeous color choices available, you can't go wrong with these long-blooming flowers. Personally, I like mixing different color combos — like pink and lavender or magenta and purple — for a vibrant color show. Deadhead the spent flowers and keep them well-watered to help them thrive all season.

Annual geraniums (Pelargonium) are a classic choice for window boxes. The colorful flowers stay upright while the scalloped leaves fill up the box with lush foliage. Just keep the spent flowers trimmed to keep the new buds coming, and these will flower well into autumn. There are many colors and types available; I love the two-tone flowers of the Martha Washington geraniums, which come in many rich colors, and some trailing geraniums, like ivy geraniums, look great in window boxes with their cascading growth habit. There are also some heat-tolerant geranium varieties for sunny locations.

These colorful edible flowers (try them in salads!) look lovely in window boxes and bloom throughout the summer. You can grow nasturtiums (Tropaeolum) easily from seed right in your window box: just sow seeds directly after the last frost date in spring. The trailing foliage drapes nicely over the side of the window box, but in intense summer heat, sometimes the leaves can get a bit crispy. Keep the plants watered and trim off any dead leaves to keep them looking fresh. I like to mix these with marigolds for a bright, colorful arrangement.

This has become one of my favorite summer annuals for containers. The compact size and glowing colors of verbena are perfect for window boxes. Once the flowers are done, the little clump will start to dry out: just snip it off neatly, and more buds will be on the way, providing lively blooms all season. Annual verbenas come in gorgeous colors, including an array of luscious pinks, reds, and purples.

These sun-loving annuals are also drought-tolerant, so they're perfect for planters that get lots of sun. They do sometimes need a bit of deadheading to clear up any dried flower buds, but otherwise, portulacas are very low maintenance. They grow easily from seed, or you can get young plants to transplant at nurseries. They come in many vibrant color mixes, like 'Sundial' in brights and pastels, or try 'Happy Hour' and 'Happy Hour Pink Passion' if you want an assortment of vivid pinks. I find that in sunny containers, these will often reseed themselves the following season.

If you want a bit of fragrance for your window boxes, I recommend stock flowers (Matthiola incana). The delicate, clove-like scent is lovely and not too overpowering. Stock flowers are an old-fashioned cottage garden favorite and come in an array of cool-toned colors from white to dark purple and many shades of pink, which accent the grey-green leaves nicely. Once the first flower spikes are done, trim the stem, and you'll get more buds for a second round of flowers. These bloom well in partial shade to full sun.

Lobelia works as a wonderful "spiller" or "filler" for window boxes. The delicate flowers form a soft cloud of color that looks great with other annuals. These bloom well in partial shade, too. I love the different blue shades, but they also come in white, lavender, pink, and purple. Once the first round of flowers starts to fade, just gently shear the stems back a few inches, and you'll get fresh buds in no time. Try sky blue lobelia flowers with hot pink petunias, or lavender lobelia with pale yellow and purple calibrachoa for a vibrant display.

These spiky, fuzzy flowers make a statement in the window box and are very sun-tolerant. The vivid colors really glow on a sunny day. Keep them deadheaded so the flowers and leaves stay fresh-looking. These come in a few different forms, including the curvy "cockscomb" shapes and the plumed, feathery varieties, all of which create dramatic textures in window box displays. Try them with contrasting shapes like verbena or petunias, and combine bright colors for an eye-catching look.

Snapdragons (Antirrhinum) make great annuals for window boxes because the flowers keep blooming for weeks or even months. There are shorter snapdragons that make great "fillers," and tall ones, like 'Rocket' or 'Chantilly,' that produce a center spike for "thrillers." The taller varieties also grow side stems that later form more buds and create a trailing shape for, yes, you guessed it, "spillers"! These colorful flowers are very versatile in containers; just remember to snip off spent flowers, and they'll keep going through the first frost and beyond.

The many varieties of trailing sedum — some of which have gorgeous flowers — make a great choice for a sunny window box display. They're resilient, drought-tolerant plants that aren't fussy about soil and tuck happily in among other flowers or will fill a box on their own. Snip spent flowers to encourage a second round of blooms. Some also have colorful foliage, like the 'Sunsparkler' series, which includes vivid berry-colored 'Wildfire' or 'Dream Dazzler,' with pink-edged, blue-green leaves.

Dianthus comes in a few different forms, but the ones that work best for window boxes are the small clumping plants sold as annuals (though they do come back for three or four years) known as 'China pinks' (Dianthus chinensis). They come in a wide array of solid and bi-colors in hues of white, pink, purple, and red. Shear off the first round of spent blooms, and a second round of buds will arrive quickly. They thrive in partial or full sun with regular watering.

Marigolds are often seen in vegetable gardens for their usefulness as an insect repellent planted near tomatoes, but they're a handsome addition to container gardens, too. These easy-care annuals have a long blooming season, and they come in a variety of shapes, sizes, and colors. French marigolds and African marigolds are the most popular. With colors ranging from creamy white to deep red and many shades of yellow and orange in between, they add an easy pop of color to window boxes and need only occasional deadheading to keep them vibrant.

Impatiens are colorful, shade-loving annuals that offer long-lasting beauty through the summer months. They're a great addition to window boxes because the plants tend to act as "spillers" and fill in bare spots readily. There are sun-loving impatiens, too, with glossy leaves and bigger flowers. These summer favorites come in a huge range of colors and just need regular watering and a bit of deadheading to bloom all season long.

Wax begonias are another shade-loving annual that performs very well in window boxes. The pink, white, or red flowers keep coming all season, as long as you do a bit of light deadheading every few days. The thick, glossy leaves stay fresh, and they come in shades of light or dark green or deep bronze to accent the delicate but bright flowers.

These tiny flowers are sturdier than they look, and the root systems are strong, letting sweet alyssum (Lobularia maritima) hold its own, draped over the edges of a window box for the entire season. Shearing off the first round of spent blooms will encourage new buds and flowers. These fragrant dainties also attract pollinators. The white ones are popular, but sweet alyssum also comes in shades of pink, lavender, magenta, and dark purple.

These colorful flowers somewhat resemble petunias, but with rounded petal edges and contrasting colors in their centers. Calibrachoas, also known as "million bells", has a growth habit similar to petunias and will fill in your window boxes nicely as a filler and spiller flower. They come in a huge array of colors, with some intriguing bi-color varieties, and a great range of juicy orange shades like 'Tangerine Punch' and 'Coral Sun'.