The Best Plants For a Window Box

Window boxes bring colour to your windowsills and windows, can enhance the curb appeal of your home and provide a great introduction to gardening. For green-fingered city dwellers, window boxes can create gardening space you might not have realised you had and you’ll be surprised at how much you can grow in them.

“Window boxes are extremely versatile,” says Everest ambassador, Chartered Horticulturalist and plant expert David Domoney. “It’s possible to grow a huge range of plants in one, whether you favour vibrant flowers, striking foliage plants, fresh herbs or even fruit.”

What To Consider Before Planting A Window Box

Before you can start your planting, there are a few things you should consider as these will determine what types of plants will thrive in your window box.

Location And Light Levels

Window boxes can be placed on deep ledges in front of your windows, hung from railings or balconies or fixed to wall brackets.

To choose the right plants for your windows, you’ll need to check your growing conditions. Is your window sheltered, or more exposed? Which way does it face? South-facing windows will receive strong, direct sunlight throughout the day, while north-facing windows have softer, lower-intensity light and are generally cooler. Exposed spots, on the other hand, can cause containers to dry out more quickly.

Weather And Seasonal Changes

Your growing conditions will change throughout the year. Summer brings more hours of sunlight and higher temperatures, while winters will be colder with more rain, wind and frost. Some plants, like hardy evergreens, are able to survive throughout the year, but others will need some help. During summer, for example, you should water your plants more frequently to prevent their soil from drying out, while lining your boxes with black plastic or bubble wrap during the winter can help your plants withstand colder conditions. Some plants will need to be moved to a warmer location during winter, or simply grown seasonally.

For a vibrant year-round display, planting a mix of perennial and annual species is your best bet.

Window Box Materials And Drainage

Exposed to the elements, window boxes tend to be larger and tougher than indoor pots, but come in different shapes, sizes and materials, including terracotta, plastic, metal and wood. These have different properties: terracotta is porous, for example, and may work better on warmer windowsills, while metal can become hot in the summer and cool in the winter. Almost any container can be upcycled as a window box, so it’s a good opportunity to get creative.

Whatever container you choose, the golden rule is that it must have drainage holes. These prevent plants from waterlogging and should be kept clear. Adding crocks (pieces of broken pots or stones) to your box before planting can also help with drainage.

Don't forget, if you install a window box, always make sure it is securely held in place and can't fall or injure anyone.

Best Flowering Plants For Window Boxes

Flowers bring a burst of colour to your window box and thankfully, there are varieties for all growing conditions.

Geraniums (Pelargonium)

“Geraniums are popular, some would even argue essential choices for a window box,” says Domoney. “They are easy to grow, eye-catching and come in hundreds of colours, patterns and varieties, so there is something for everyone.”

Zonal geraniums are one of the most common varieties, with rounded leaves and tight clusters of brightly coloured flowers on stalks. Regal geraniums, meanwhile, have larger, patterned blooms, while stellar geraniums have distinctive star-shaped flowers. Scented-leaf varieties can even smell like other plants.

One of the big benefits of geraniums is that they have a long flowering season. They flourish in warm, sheltered, sunny spots. Covering your geraniums or moving them indoors will help them to survive during cold winters.

Petunias

Petunias are guaranteed to brighten up a window box, with their showy, trumpet-shaped flowers that come in a range of colours, from pretty pastels to rich reds, oranges and fuchsias.

Trailing varieties, like Easy Waves or Surfinias, are a great choice for a window box, with their colourful flowers tumbling over the sides. They tend to be more weather-resistant than other cultivars, with long-lasting blooms.

Like geraniums, petunias will grow best in a sunny, sheltered spot, but will not tolerate extremes of temperature. They might need extra shade in summer, for example, and will need to be moved into a warm, frost-free location in the winter.

Fuchsias

If your windows are shadier or even north-facing, fuchsia is an excellent option. Hardy varieties will grow in almost any window box, provided that they are sheltered from cold winds.

Fuchsias have colourful, pendant-like flowers which hang suspended from their stems like tiny chandeliers. Some grow more upright, while trailing varieties work particularly well in window boxes.

Most fuchsias are low maintenance, requiring extra water during hot, dry periods and some deadheading to encourage new growth. Hardy cultivars can be kept outdoors over winter, but may need some protection during cold snaps, while tender varieties need to be moved to a warmer spot.

Best Herbs And Edibles For Window Boxes

A sunny window box is a wonderful place to grow fresh herbs, salad leaves or even fruits like strawberries. As well as complementing your cooking, many of these plants thrive on windowsills too at certain times of the year.

Basil, thyme and mint (Ocimum basilicum, Thymus vulgaris, Mentha)

“Basil is one of the best money-saving plants you can grow,” says Domoney. “Huge quantities of leaves can be harvested regularly from a single packet of seeds.” Basil plants need sunny, sheltered windowsills, and can only be grown outdoors during the summer months. Sweet basil, with fragrant green leaves, is the kind most commonly sold in supermarkets, but other varieties include Thai basil, lemon basil and even purple basil, with darker coloured leaves.

Thyme, with its tiny, glossy leaves, may taste best in spring and summer, but can be grown and harvested all year round. Mint, on the other hand, is perennial, meaning that it will re-sprout every spring. Both prefer warm, sunny spots.

Mint plants will produce spear-shaped white or purple blooms in summer, so can add colour to your window box too. In fact, it is best grown in containers, because it spreads quickly.

Lettuce and salad greens

Homegrown salad leaves are quick-growing, tasty and can often be picked repeatedly throughout the year. There are hundreds of varieties to choose from, so it’s best to go with your favourites.

Young, tender lettuce or salad varieties are particularly quick to grow, because they are harvested when the leaves are still young. As a result, they often have a milder flavour.

Popular varieties include the compact Little Gem, butter lettuce, spinach or rocket. These are best planted in spring.

To boost your supply over winter, opt for the likes of romaine, winter gem, chicory, chard or kale, all of which can be grown on a sunny windowsill.

Strawberries (Fragaria ananassa)

“Strawberries are one of my favourite plants,” says Domoney. “They taste even better when you’ve grown them yourself.”

Strawberries are compact, attractive plants with green, serrated-edged leaves, small white or pink flowers and delicious fruit, of course. They grow well in window boxes and, depending on the varieties you choose, can be grown for months.

Summer-fruiting strawberries are most popular but can only be harvested for a couple of weeks. Perpetual varieties bear smaller fruits but grow throughout the summer and autumn, while smaller alpine strawberries (Fragaria vesca) are extremely self-sufficient and have a longer growing season.

Strawberries should be planted during spring or autumn on warm, bright, sheltered windowsills. Keep them well-watered in hot weather.

Low Maintenance And Evergreen Options

Ivy or trailing vinca (Hedera or Vinca minor)

“Trailing plants, cascading over the edges of window boxes, can help to soften the edges of your display. They’ll add interest and look good all year round,” says Domoney. Ivy, with its glossy green leaves, and trailing vinca, which produces small violet flowers, will grow on any windowsill, whether it’s sunny, shady, sheltered or exposed. Both plants require very little care and, being evergreens, will maintain their colour throughout the year.

English ivy is most common, but also has yellow and white cultivars with intricately patterned leaves. Other varieties produce different shaped or coloured foliage. Boston ivy, for example, has a rich, autumnal colour, while Dentata (also known as Persian Ivy) has larger, heart-shaped leaves with grey-green and cream patterns.

Ivies are important for wildlife like birds and bees, but they can also benefit our homes. Research shows that ivy can keep buildings cool in summer, while reducing damp in the winter.

Both ivy and trailing vinca are vigorous, fast-growing plants, so it’s advisable to trim them back in spring.

Heathers and small shrubs (Calluna vulgaris)

Heather might remind you of rugged heathland or wild moors, but planting it in your window box can bring some of that drama to your home. This evergreen shrub produces lots of tiny, bell-shaped flowers which can bloom throughout the year in pinks, purples, reds and whites.

A hardy plant, heather requires very little care. It should be planted in ericaceous compost, either in full sun or partial shade. Choose the right mix of species, and you could have flowers throughout the year. Calluna varieties, for example, flower in summer and autumn, while Erica blooms in winter and spring.

Heathers can be planted alone, or work well with other small, evergreen shrubs. Pyramid-shaped dwarf conifers can provide contrast in height; juniper (Juniperus communis), with its aromatic, needle-like leaves, can bring different colour, texture and scents. Like heather, both will maintain their foliage year-round.

Succulents and sedum (Hylotelephium)

Succulents are plants with thick, fleshy leaves, which they use to store water. Sedums are a type of succulent, with colourful leaves held on upright stems. In the summer, they produce clusters of small, star-shaped flowers which bloom in whites, pinks and reds. Sedums and other succulents grow best in warm, sunny conditions. Succulents may need to be protected or brought inside over winter, but sedums are extremely hardy. They can tolerate winds, frosts, dry soils and even waterlogging – although they prefer well-drained soil.

The Mexican snowball (Echeveria elegans) is a popular succulent, with symmetrical, silvery-green rosettes and pink flowers which bloom from the top of long stalks in late winter and spring. Houseleek (Sempervivum) also grow in rosettes of wide-ranging colours, and is very easy to take care of, while lace aloe (Aristaloe aristata)’s spotted, lance-shaped leaves can bring height to your display.

Best Plants For Window Boxes All Year Round

The aim is to create a window box which brings life and greenery to your home all year round. There are two ways of achieving this: changing your display with the seasons, or opting exclusively for evergreens and hardy perennials.

Seasonal Planting Strategy

Many gardeners choose to combine a selection of evergreen plants with seasonal highlights. The evergreen species will flourish throughout the year, but this strategy means that you avoid a full plant rotation every season.

In the summer, you can take your pick of most flowering or foliage plants, whether it’s bright petunias or fragrant basil. Winter is the main challenge for plants kept outside, as they cannot withstand the cooler temperatures. Plants like fuchsias, petunias and tender geraniums will need to be moved inside or to a greenhouse. Some varieties are grown as annuals, meaning that you’ll need to plant new ones in spring.

“Rotating plants can be an opportunity to play around with seasonal colours,” says Domoney. “Try delicate, pastel-coloured blooms in spring, for example, and rich oranges and reds in autumn.”

Hardy Perennials For Year-Round Interest

“Don’t underestimate your hardy perennials. They too can be showstoppers and are arguably the most important element of your window box,” says Domoney.

Dwarf conifers make excellent plants for a window box. Small juniper, cypress or spruce plants, meanwhile, add colour and texture. Ivies or trailing vinca have the benefit of disguising older plant boxes and adding interest by spilling over the sides.

Despite their delicate looks, ferns are also hardy options that cope well on shady or north-facing windowsills. Similarly, look for ornamental grasses like the blue-grey Festuca, feathery Stipa tenuissima or Deschampsia cespitosa, which flowers in the autumn and changes from green to gold and brown throughout the year. Coral bells (Heuchera) come in a rainbow of striking colours, from greens to purples to oranges. They grow best in sun or partial shade.

Evergreens and perennials can also produce flowers. Some heather varieties, for example, flower late in winter, making it feel like spring has come early. Perennial cyclamen, hellebores and pansies will also bring bright blooms to dull winters.

Alternatively, thyme and rosemary are evergreen herbs that can be harvested year-round. Winter lettuces like chard, kale and chicory can keep your windowboxes full in the colder months.

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Tips For Caring For Your Window Box Plants

Watering And Feeding

Because of the limited size of a window box, your plants will need regular watering and feeding.

Window boxes can dry out easily, especially in sunny or windy locations. Ensure that their soil is kept moist with regular watering, particularly during the summer. Adding water-retaining granules, homemade compost, mulch or even biochar (a form of charcoal made from organic material) can boost your soil’s ability to hold moisture.

It’s also possible to buy self-watering window boxes. For a DIY option, you can poke small holes in the cap of a water bottle, flip it upside down and place it in your window box. This will provide a slow, steady water supply.

During the UK’s wet winters, it’s important to prevent waterlogging by keeping your box’s drainage holes clear. If it is perched on a ledge, you might want to raise it up on feet to allow water to escape. It may also be helpful to remove any trays underneath your box before winter to stop your plants from sitting in water.

Feeding your plants regularly will also help them to thrive. Adding a slow-release fertiliser to your compost boosts your plants’ nutrients, while using a liquid feed regularly during the spring and summer is also recommended.

Deadheading And Pruning

Once your flowers have bloomed, removing the faded heads or yellowing leaves (known as “deadheading”) will help to encourage regrowth. You can deadhead plants using your fingers, with scissors or secateurs. “Cut off the heads, but do not remove healthy leaves,” advises Domoney. “Your plants need these to photosynthesize.”

Pruning can help to keep more vigorous species like ivy or mint under control. Start by pruning from the top of your plant, cutting back dead or damaged branches to the nearest bud or branch. Not only is this good for your plants’ health, but with species like juniper, pruning can also shape the foliage and maintain the plant’s size.

Keep an eye on your plants’ roots too. Pruning will prevent quick-growing species from taking over, or absorbing more than their fair share of the soil’s nutrients. To do this, you’ll need to remove the plant from the box and trim back the old roots. Gently return the plant with some new potting soil, and fertilise after pruning. The best time to do this is during the winter or spring, before the new growing season starts.

Final Thoughts

If you wish you had more space to garden, window boxes might be the answer. They provide versatile, productive and easy-to-maintain growing spaces in any home, and will brighten up your view whenever you look out of your window.

Choose the right plants for your windowsills, and you can create a beautiful visual display whether you want to grow colourful flowers, greenery, fragrant plants, fresh herbs or fruit. If you’re willing to rotate some of your plants, you’ll have a window box that changes with the seasons and looks good all year round.

Windox boxes will also draw attention to your windows themselves. Everest offers a range of beautiful windows which will match your property, boost the energy efficiency of your home and provide the perfect backdrop to your window box display.