Window Boxes

Window-boxes are more popular than ever. With such a wide range of styles, shapes and prices, it’s easy to find the right boxes for your home, both indoors and out. Window-boxes enable you to create a colourful mini-garden, even in the most unpromising urban setting. Usually placed outside, they are also effective standing on a sill indoors and filled with house plants.


Before buying, consider cost, durability, maintenance and style. Fixing is also important, and unless you support a window-box on wall brackets beneath a window, it has to fit on the sill.

Always buy the largest window-box you have room for and can afford. Besides making a better show, the larger boxes are easier to keep watered. Depth is as important as length.

For outdoors, try to stick to one style for a unified effect. Many styles come in lengths to suit narrow and wide windows. Indoors, each room can have a different type, depending on your décor.

Some window-boxes have drainage holes, some don’t. It’s easier to look after the plants if there is good drainage, so you may want to cut or drill drainage holes if none are provided. You need a drip tray indoors, and also outdoors where water is likely to discolour the wall as with white-painted stucco.

Materials and styles

Plastic window-boxes are cheap, lightweight and widely available. Polypropylene moulded window-boxes come in white, brown, green, black and stone, with matching drip trays, and in plain or ribbed design. Some have built-in self-watering systems.

Ornate styles can look odd, since plastic is an obviously modern material, and giving it historical ‘airs’ doesn’t really work. Plastic, especially rigid polythene, gets brittle and discoloured with age.

Moulded fibreglass is used to make reproduction lead window-boxes. These 3 are expensive, but more convincing than plastic reproductions, and the swags and figures are especially decorative.


Wood is attractive, natural or painted. It’s a good insulator, protecting roots from temperature extremes, and the easiest material for building window-boxes, if you’re a DIY fan. Hardwood window-boxes – iroko, oak, teak, cedar and mahogany– are expensive, but long-lasting. Hardwood boxes have a natural appeal. If using softwood window-boxes, make sure the wood has been treated. Cheaper softwood window-boxes need treating with preservative before use, and painted wood needs regular re-painting. Manufactured styles include solid and slatted panelling. Rustic-style window-boxes may be made to order. A decoratively painted window-box needs a simple planting scheme to complement it. Here, grey, green and white leaves and flowers are combined.

Terracotta has an old-fashioned charm. Though expensive, terracotta window-boxes are long-lasting and maintenance free, provided you don’t drop them. Avoid glazed terracotta, which can crack

Small, simple containers can be used to show off bright blooms on a narrow sill indoors. If you live in an area with severe winter frosts, it’s best to choose another type of window-box altogether. Terracotta is not a good insulator.

Styles range from the simple to the ornate, with figures, swags, leaf patterns or French vertical fluting.

Reconstituted stone is similar to concrete, but with selected aggregate for a realistic stone-like look. Reconstituted stone window-boxes come in a variety of finishes: limestone, red or yellow sandstone and slate; and in natural or antiqued shades. Surfaces can be smooth or rough hewn.

Styles also vary from simple to ornate, with moulded figures, animals and decorative patterns on the surface. Some are authentic reproductions of Regency, Victorian, Georgian and even Renaissance designs.

Wrought iron ‘mini’ balconies have solid or slatted bases, with decorative ironwork guard rails. Fixed to sills or cantilevered from walls, they can hold window-boxes, or a collection of flower pots, for a similar effect. Some older houses have permanent, built-in iron bases and rails.

Supporting and fixing window-boxes

Even lightweight plastic window-boxes are heavy when filled with moist potting mixture and plants. It’s tempting to ‘make do’ by resting a window-box on a sill, but safer and more sensible to secure the box before filling and planting it up. This is usually more important outdoors than indoors – especially if the window-box is well above the ground.

Window-boxes under windows

If a window opens outwards, or there is no sill or only a very narrow one, fix the window-box under the window so that the box (and plants) do not obstruct the opening. Choose a box at least as wide as the window frame, and support it from below with a pair of strong steel angle brackets; those with upturned ends give extra security. Wrought-iron brackets are attractive, but must be sturdy. Check they have been treated against rust.

To fix the brackets, hold them in place and check that they are vertical with a spirit level. Using a pencil, mark the positions of all the screw holes. Use the slower speed of a two-speed masonry drill to make the holes, then tap in wall plugs. Make sure they fit tightly, then screw the brackets in place.

As a double safety measure, attach eye screws to the two lower frontcorner ends of the box. Run strong long-arm hooks, wire or chain from the eyes to hooks screwed into the wall on either side of the window frame, 25— 30cm (10-12 inches) above the bottom of the window.

Window-boxes on outdoor sills

If you have a usable sill, the job is easier. Many sills slope away from the house to throw off rainwater. If so, insert wedges, treated with preservative, under the window-box to make it level. Unless the window has a built-in iron guard rail, use hooks and side chains to secure the box to the wall, as above.

Self-watering window-boxes

Self-watering window-boxes contain built-in reservoirs under the planting section. The reservoir can hold several weeks’ worth of water– ideal if you’re going on holiday in the hot summer months. It is filled through an opening in the top or side of the window-box, and a fibre wick takes the water up into the potting mixture, as it is needed. Some have water level indicators, which let you know when reserves are running out. There are several styles of self-watering boxes to choose from.

Do’s and Don’ts


  • Place a layer of drainage material in the bottom of a window-box before adding the potting mixture.
  • Water indoor window-boxes carefully. Water can get trapped underneath and damage wooden sills.
  • Remember terracotta window-boxes need watering more frequently, as water from the compost evaporates through them.


  • Buy terracotta window-boxes without checking that they’re frostproof.
  • Rest wooden window-boxes directly on sills outdoors. Raising the container on wedges or blocks allows the air to circulate and prevents rot.
  • Forget that overhanging eaves and masonry can prevent rainwater reaching window-boxes. Water generously, as needed.

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