Window boxes add something very special to the exterior of a property. They are ideal for those who live in apartments as this may be the only way they can enjoy a hobby of gardening. They add color and interest to windowsills, walls and balconies. Seasonal plants and bulbs as well as herbs and vegetables can all be grown in a window box. Window boxes are an important part of container gardening, but to ensure success and safety there are a few rules you need to follow.
The first step is to decide on the type of window box you want to use, the color and material that will suite the place your window box is going to be positioned in. Window boxes can be bought in a variety of materials, such as , plastic, terracotta, metal, concrete or wooden. Wooden is probably the most popular material and can either be painted or stained, but it must be weather treated with plant safe wood preservative.
Types of Window Boxes
There are 3 main types of window boxes: Unlined, lined or self-watering.
Unlined Window Box
In an unlined window box the compost is placed directly into the container. These types of window boxes can sometimes be difficult to attach, so it is best to buy the best quality you can.
Lined Window Box
Lined boxes will have one or two liners to hold the compost in. These should be include with the box. This is a useful feature if you want your box to look at it’s best for longer.
Self-watering Window Box
A self-watering window box has a built in water reservoir. These can be very beneficial if daily watering or very hot conditions make it difficult to maintain sufficient watering. They are also very useful if away on holiday. They are usually made from plastic or fibreglass.
Size is also an important consideration when deciding to make a window box. A minimum depth and width of 8in (20cm) is needed. If less than this your plants will dry out too quickly. Ideally your box should be just a little shorter than the windowsill you are going to site it.
Secure fixings are essential, especially if it is going to be attached to an upstairs sill. Frequent watering will also add to the weight. Depending on the plants you are to grow, the box will have to be positioned either in a sunny spot or for some plants in a shady spot. So check the growing instructions before you plant.
Watering a window box is often more difficult than a container as they receive less rain water. Make sure you place your window box where you will be able to water it easily. Always attach the empty window box to the wall before planting as moving and attaching a filled box is not only very heavy it can be very dangerous.
Fixing your window box on a sill will depend on how the window opens and the type of sill you have. For wide sills and windows which do not open outwards, wooden wedges are used to level the box on the sloping sill. This also allows water to drain away. Angle brackets are then used to secure the box to the wall.
For narrow sills or no sills and windows which may open outwards, wall fixing is required. Strong steel brackets are needed to support the container. The screws and wall fixings should be strong enough to support the weight of the window box, allowing extra weight for; compost, plants and water. The back of the box should also be screwed to the wall.
Once having fixed your window box to the sill you are ready to start planting. The first step is to add a drainage layer. Cover the holes with crocks or a fine mesh. A 1in (2.5 cm) layer of gravel can be added to help with drainage, but if weight is a problem leave this out.
Next add your compost layer. Soilless compost is best for this as it is light weight. Press gently down with your hands. Plant your chosen plants, leaving a 1in (2.5cm) watering space.
As with all containers the compost must not be allowed to dry out. Watering everyday may be necessary. You should start to feed your window box with a liquid fertilizer after about 8 weeks from planting.