10 steps to the perfect window box display

Window boxes are a pretty easy way of bringing colour to your outdoor space, however small. With space at a premium and a growing population of savvy urban gardeners, planting a window box is a novel way to create instant impact.

It's no surprise that city dwellers in the capital are on average three times more likely to feature window boxes at the front of their home compared to residents in other areas of the country. While window boxes are traditionally placed on a window ledge (fitted with brackets), you could also hang your window box planter on a fence or balcony.

You can really experiment with what you plant too, from specially selected smaller ranges of climbers, shrubs, roses, vegetables and herbs.

window boxes
Pelargonium Europe

How to plant a window box

When planting a window box, all you need is a container or trough, compost, mulch and, for quick results, ready-planted pots. Ann-Marie Powell, award-winning garden designer, TV gardening presenter, journalist and author, takes us through all the steps on how to plant up a window box.

1. First make sure your window box is clean. By giving it a good scrub you’ll help to keep pests and diseases at bay.

2. Drainage holes prevent waterlogging. Cover them with old crocks – this will stop the earth becoming impacted around the hole and allow water to drain away.

3. If you have a terracotta window box, line it with a plastic bag to reduce the need for watering. Be sure to cut several holes in the bag, particularly over the drainage holes.

4. Provide a drainage reservoir by adding a layer of gravel to the bottom of the pot to roughly a tenth of its depth.

5. Fill the pot with good quality compost to two inches from the top. Never use garden soil as this won’t contain the right nutrients.

6. Add pre-soaked water-retaining granules into your compost to keep it wet for longer. They increase dramatically in size when watered, then release water back into the soil when your plants need it most.

7. Mix in a slow- or continuous-release fertiliser with your compost.

8. Add your plants, firming the compost around them to ensure that they’re well grounded and to knock out any air pockets from the compost.

9. Finally, add some mulch (gravel, glass chippings, cobbles) to the surface of the compost, leaving at least half an inch from the top so that when you’re watering, it doesn’t simply spill out over the edge. Mulch will provide a polished finish, keep compost in position, help prevent water evaporation and stop weeds from seeding so easily.

10. Once it’s planted, ensure the window box is well secured and well watered – containers, particularly if they’re terracotta, can dry out quickly in the sun and wind. If you’ve provided good drainage, it’s difficult to overwater a containerised plant; most will need watering at least once a day through the summer, but the results will be worth it.

window boxes
Don White - Getty Images

What planters to use?

There are no strict rules but a container, trough (terracotta, iron or galvanised steel) or balcony hanging planter is your best bet here. Or, you may prefer a window basket, where you can put a series of small pots inside, like this wire design from Crocus. You can also upcycle crates and old containers, just ensure there are drainage holes. Importantly, for safety (and to prevent theft), secure your window box to the wall with metal brackets.

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