Our pick of the best plants for window boxes

Now summer is upon us, we’ve written you the ultimate guide to the best plants for window boxes ahead. After all, pretty-planted windowsill displays are an easy way to give your home an instant uplift. We’ve recruited help from Modern Gardens Magazine contributor Louise Curley to help with choosing the best outdoor plants for your home, as well as the right containers to house them in.

Similar to hanging baskets, window boxes offer a splash of green, a splash of colour to an area that may have previously been dull. You could even add matching boxes to both upstairs and downstairs sills for more impact. As you all may know, flowers clean the air of harmful toxins and can improve our wellbeing. Not only will your picks look fresh, but they will freshen the air, also. All the more reason to hang a window basket outside your bedroom window – next to your house plants.

Best plants for window boxes at a glance:

• Neon-like coloured blooms: Nemesia 'Sunmesia Tropical'
• Star-shaped violet flowers: Campanula carpatica
• Best plants for summer window box: Flowers for a Summer Window Box Collection
• Unusual flower pick: Pelargonium 'Australian Mystery'
• Marirgold-esque saucers: Arctotis × hybrida hort. 'Orange Prince'

Finding the ideal plants for your window box project doesn't have to be a tricky task. First, the window box you should choose very much “depends on the type of windows and sills you have,” says Louise. When opening your window, you don’t want to damage your plants – and having easy access for watering and general maintenance is preferred. Before you buy, make sure to check if your windowsill is wide enough to take a hook or bracket to secure the window boxes.

Louise reminds us that compost will weigh the planters down, so invest in separate fixings for security. Another drawback of window boxes: “bear in mind that water draining from the box may discolour your sills or walls,” says Louise. So, consider using one with a drip tray underneath. This way, your beloved plants won't be causing any issues - and will look healthy and make a world of difference to your home.

Best plants for window boxes

For a delightful springtime or summer display, we have found the best plants for window boxes.

Vibrant hues

For colour from June to September, pack your window box with a selection of long-flowering plants.

Soft and floaty

If you’d prefer something a little wild looking, try this combination of Mexican fleabane, with its frothy haze of white and pink daisy flowers, and the soft pompom-like, vibrant green blooms of sweet William ‘Green trick’, says Louise.

Simply stylish

Pelargoniums thrive in a sunny spot, says Louise. "They will flower from May to the first frosts and need very little attention." Luckily, they come in a variety of colours to suit all tastes. These range from "pretty pastels to rich jewel-like colours, and some, such as Brunswick, have a heady, fruity scent". You can also choose from trailing ones that are referred to as ‘ivy-leaved’, such as the Double Trailing Black.

Pretty peach

Trailing black-eyed Susan will envelop any container, which is "perfect if you want to cover an inexpensive plastic window box", says Louise. It flowers from June right through until the first frost.

However, Arctotis ‘Flame’ provides height as it grows to about 40cm with "slender stems topped with flame-coloured exotic blooms" from May to October.

FAQs

What are the best window boxes?

When choosing a window box, Louise has some suggestions. This may seem obvious but is an essential step: Make sure to measure your windowsill so your box can fit. After all, you don’t want to have to fuss around with returns. We’ve included dimensions in our top picks. Not to worry.

Louise says to “always buy the largest and deepest planter possible that fits the space.” A larger planter won’t dry out as quickly. Also, “there’ll also be plenty of space for roots to grow making healthy plants and a more attractive display.” Sounds ideal, right?

We’ve avoided listing plants that are tall, bulky or top-heavy. “If you have windows that open outwards you may need to stick to low-growing plants,” says Louise. However, if you have windows that open upwards “you can experiment a bit more using slightly taller plants.”

How do I plant a window box?

Louise Curley has a step-by-step guide on how to plant a window box.

First, Create Drainage. By adding a layer of broken pots to the bottom of the planter, you can help with drainage. After all, window boxes need plenty of drainage holes as “waterlogged compost will cause your plant’s roots to rot.” So, Louise suggests checking when you shop or adding holes by drilling.

Next, Fill It. According to Louise, this should be about halfway with compost that has added plant food. For example, Miracle-Gro All Purpose Compost may serve you well. This way, plant food is “continuously released, keeping your plants fed… for up to three months.”

After this, Plant Up. Create your own design by carefully tipping “out the plants from their pots and position in the planter.” When you’re happy, fill the gaps around the plants with more compost “and firm it down with your own hands.” Avoid overspill by keeping the compost lower than the rim.

Lastly, Water It. This should be done thoroughly, says Louise, so that “water runs out of the base.” Remember: water boxes will dry out quickly. To avoid any issues, check the compost every couple of days, “more frequently in hot weather,” says Louise. If it feels dry, water it with half a watering can.

What to read next:

Best climbing plants to add height and colour

Best ornamental grasses for an elegant and stylish garden

Best plants for privacy to protect your garden retreat

Piper Huxley is a Homes, Garden and Wellness Product Writer for Modern Gardens Magazine, an all-rounder. When she’s not writing about houseplants, she’s tending to her own growing collection…