April Can Be Just As Colorful For Window Box Gardeners – Plant These Flowers Now and They’ll Dazzle Until Fall

Small-space gardening doesn't have to mean limited planting. In fact, having a window box is sufficient space to create a vibrant display that lasts from spring to fall – especially when you choose the right flowers.

If you're feeling stumped for inspiration for spring window box ideas, then turn your attention to window box flowers to plant in April. Adding these blooms now will reward you with a bright display that offers color right through summer to fall. You don't need a huge window box either, as there are lots of compact flowers that will thrive in a vessel the size of this IKEA white window box planter.

From petunias to lantana, there are options to suit every clime. Here, gardening expert and landscape designer Brandon McCormick shares his top picks of window box blooms to plant now for a dazzling display that will last for months.

1. Petunias

'Petunias are one of the most reliable choices for long-lasting window box displays,' says Brandon. 'Modern varieties, especially trailing types, will continuously bloom and spill over the edges, creating a full, lush look that lasts for months.'

Petunias are hardy across USDA zones 2-8, and it's super easy to grow petunias in pots. They're a great spiller in thriller, spiller, filler container ideas, and also work well in a hanging basket (like this coco coir lined one from Amazon).

'Remember to deadhead lightly and feed every 2–3 weeks to keep petunias blooming into fall,' Brandon advises.

You can remove spent blooms with gardening snips, like these on Amazon.

These pink petunia starter plants from Walmart are a great size to pot up in your window box.

Brandon McCormick

Brandon McCormick is the landscape design and product development director at Carlsbad Manufacturing Corporation, where he plays a key role in guiding product innovation across its family of brands, including Stone Yard, Planters Unlimited, and Hooks and Lattice. With a lifelong foundation in horticulture, Brandon brings a unique depth of plant knowledge to the built environment. His combined experience in landscape maintenance, rare plant care, and design collaboration positions him as a trusted expert at the intersection of form, function, and green innovation.

2. Verbena

'Verbena is a heat-tolerant, trailing bloomer that thrives in containers and continues flowering well into late summer and early fall,' Brandon describes.

There are lots of types of verbena to grow, with the tallest varieties (such as 'Argentinian Vervain' at 5-7ft) making great back-of-border plants. For a window box or container, opt for a more compact, bedding plant variety, like the 'Quartz' verbena (seeds available on Amazon), which is hardy across USDA zones 7-11.

'Place it in full sun and deadhead verbena lightly mid-season to refresh growth and encourage a second flush of blooms,' Brandon advises.

You can grow verbena from seed (with these verbena seeds from Burpee), starting them early indoors between late winter and early spring.

Bonus: This is a great plant for pollinators, so you can expect bees and butterflies to flutter around your window box all spring and summer.

3. Lantana

'Lantana is an excellent choice for warmer climates, producing vibrant clusters of flowers that attract pollinators and persist through heat and drought conditions,' Brandon says.

You can grow lantana across USDA zones 8-11, and it thrives in pots, appreciating good drainage. It comes in a wide range of colors, including the two-tone pink and yellow lantana photographed above.

'Ensure excellent drainage and full sun,' says Brandon. 'Lantana performs best when slightly stressed rather than overwatered.'

Don't forget to prune lantana with clean and sharp pruning shears (like these Fiskars ones on Amazon) to keep it shapely and to remove dying and leggy stems.

Find a lantana plant at Burpee.

4. Pelargoniums

'This is another standout for sustained color,' says Brandon. 'Their upright growth adds structure, and they tolerate sun and heat exceptionally well, making them a dependable anchor plant in window boxes.'

You can grow pelargoniums across a wide range of climates, but they thrive best in USDA zones 9-11.

They come in a wide range of color combinations, from these red pelargoniums on Amazon to these white pelargoniums on Amazon. For an enticing fragrance every time you open the window, opt for scented pelargoniums (you can find a citronella plant at Walmart, for example).

'Always allow the soil to dry slightly between watering to avoid over-saturation and encourage stronger flowering,' Brandon advises.

You can use this soil moisture meter from Amazon to identify when your window box's soil has sufficiently dried out.

5. Million Bells

'Calibrachoa, or million bells, offers a smaller, petunia-like bloom but with even more prolific flowering,' says Brandon.

'It’s ideal for creating dense, cascading color that holds up through the entire season,' he describes.

Containers like window boxes are ideal for growing million bells because these blooms need lots of drainage.

'Use a well-draining potting mix (like this Miracle-Gro potting mix at Walmart) and avoid overwatering. These perform best when roots stay evenly moist, not soggy,' Brandon advises.

Million bells come in endless color options, including this yellow million bells plant on Amazon and this tangerine million bells plant at Walmart. They do best across USDA zones 9-11.

What to Shop

FAQs

How Often Should I Water My Window Box?

This all depends on the plants you have growing in your window box, but keep in mind the soil will dry out more quickly because it's elevated and has extra drainage. You can conduct a moisture test either with your finger or your soil moisture meter (from Amazon) to identify whether the soil has dried sufficiently for the specific plants you're growing in it.

If your window box isn't sitting on a sunny side of the house, our guide to planting a window box for shade has plenty of solutions. And don't forget to bring a sensory feel with fragrant herbs for a window box.

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