Growing plants in window boxes

If you enjoy growing house plants you will soon have every available space indoors covered with them. Whether you live in a block of flats or a country cottage, you can extend the frontiers of your house plant collection by using window-boxes. You can also use boxes on balconies, patios and roofs, outside your front door and in basement areas, where they can transform their surroundings and create an oasis of colour and greenery all year round.

Although the aspect and conditions outside your home may not seem favourable, you can choose plants that will suit the prevailing conditions. South-facing sites will be warm and sunny, while north-facing ones will be cool and shaded. East-facing situations will get strong morning sun while those facing west will have less sun and more wind. Basement areas can be either sun-traps or shaded grottoes.Growing plants in window boxes

The brighter light outdoors allows you to grow a wider variety of flowering plants than is possible indoors. Remember that the plants you choose have an important role to play in brightening up large expanses of wall, so they need to be chosen for maximum impact. Look for colourful plants, and blend the colours in pleasing combinations.

Bedding plants

These are plants that are raised annually in greenhouses and sold in the spring ready for planting out. They can be used to great effect in window-boxes. Balsam, an outdoor version of Busy Lizzie, is low-growing and has pink, red, orange, white and purple flowers. Plants with a variety of these shades will make ideal candidates for your boxes. They flower profusely all through the summer and can tolerate shady conditions.

The small-flowered bedding begonias, hybrids of Begonia semperflorens, can also be grown in shade. The flowers can be red, pink or white, and the leaves are light green or wine-coloured. Worth considering too is a delightful double-flowered version in pink with tiny tight pink rosette-like flowers. Petunias come in a ravishing range of colours. They can be plain or striped, frilly petalled or double. Shocking pink, magenta and blue-purple are some of their stunning colours. They flower all summer and do best in full sun and warmth. Mix them with Tobacco Plants for perfumed scented air on summer evenings.

French and African Marigolds, Pot Marigolds, Scarlet Sage, Mimulus, Nemesia and Pansies are all excellent for window-boxes. They vary in height from a few centimetres to 60cm (2ft).

Climbing and trailing plants

Use small-leaved Ivies (especially attractive if they have yellow, grey or white variegations on their leaves) to cover and clothe bare wall space. The trailing Ivy-leaved Pelargoniums such as P. peltatum and the hybrid ‘L’Elegante’, with white flowers and white and pink edged, grey-green leaves, make a dazzling display.

Nasturtiums and blue Lobelias, and the small-leaved form of Periwinkle will also make frothy and dramatic clouds of colour. The evergreen climber Eccremocarpus scaber, the Chilean Glory Flower, and Sweet Peas on a trellis will cover walls with colour and interest.

Seasonal displays Window-boxes can be decorative all year round. After the summer display of bedding plants is over you can plan displays for autumn, winter and spring, using plants that will flower at the appropriate season.

Preparing and planting your window-box

Modern containers are varied and the choice is wide. No longer are you confined to a plain painted wooden box. You can use boxes made of expanded polystyrene or rigid polypropylene in a range of colours. Boxes are available in concrete, or mixtures of concrete and stone, or moulded fibreglass. Sculpted terracotta troughs, too, are very popular.

Whatever sort of box you choose make sure it is fixed firmly and has drainage holes in the base. If there is no outlet for excess water the roots can be swamped in heavy rain and the plants may die. If the box is sitting on an outside window ledge, you may be able to raise the box a little on flat stones or pieces of brick. Make sure it is level so that water can drain away freely. You could also put a plastic tray underneath to catch excess water.

Before you start filling the box with compost put a layer of broken brick or clay shards in the base to help drainage. Both peat-based and soil-based potting mixtures are suitable for window-boxes. If you are making a permanent planting choose a soil-based mixture. If you are worried about the weight of the box, use a peat-based mixture.

Fill the box to within 25mm (1in) of the rim. Make sure it is evenly firm at the corners and sides as well as in the centre. Check that the surface is level.

Before you begin to plant, plan your arrangement carefully. For an all-year-round trouble-free planting you might choose from Fuchsias, small Conifers like Juniperus communis ‘Compressa’, Hebes, miniature Roses and Heathers, mixed with trailing Ivies and Periwinkles. Water the plants well before planting.

Start planting at one end and work across the box, making each plant hole large and deep enough to take the root ball comfortably. The surface of the compost should just cover the root ball. Firm each plant in well.

Allow sufficient space between the plants to let them grow and fill the box. The space between them should be about a third of their final height. As you plant take off any yellowing leaves and damaged stems or flowers, and check for insects and fungal disease. Finally, give them a good watering.

During the growing season feed and water the plants regularly. In hot weather they may need water twice a day. Check the plants regularly and pick off any faded flowers, discoloured leaves and damaged stems to keep your window-box display healthy and attractive.

Window-box plantings of seasonal flowering plants, hardy perennial plants and trailing or climbing plants can soften and transform the outside of your house.

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