A number of ready-made window boxes are available, from simple plastic trays to ornate wood. Choose one that will blend in with your house wall – the more natural-looking the better. Before buying consider how the box will be fixed. Is the sill wide and strong enough?
If not it will need fitting. Window boxes can be fitted on walls facing any direction but south and west-facing will require more watering. North-facing boxes will need shade tolerant plants.
Setting up Your Window Box
Check your window box has drainage holes in the base or at the bottom of the sides. Some plastic containers may have to be drilled through, and a saucer placed beneath the box. Cover the holes with broken crocks or stones – make a layer about 5 – 7 cm deep.
Cut a piece of sacking, or J cloth to cover the crocks. This will filter water through but will stop your compost from being washed out.
Plain potting compost is fine for your window box. You can give a nutrient boost by adding a dose of slow release plant food and water-holding gel granules. Make sure that you soak these in water first to prevent them from exploding.
Mulch your window box to help prevent drying out in summer and to insulate in winter. Mulching involves adding a moisture retaining layer on top of the existing soil, for example damp compost, manure, bark chips or gravel.
Choosing What to Grow
- Open flowers produce more nectar than some of the modern cultivars and the nectar and pollen supply is within easy reach of bees and other insects.
- Poached egg flowers are easy to grow and will attract hoverflies to pollinate and lacewings to keep pests at bay.
- Plant bulbs. Early flowering species such as crocuses, snowdrops and grape hyacinth are good for any bees that wake early from hibernation.
- Bees love clover flowers, catmint and lavender amongst others.
- Grow ferns in a shady window box, or even winter-flowering heathers (although these may take over space from other plants).
- Rosemary and other small woody plants, or trailing species such as ivy, provide year round greenery to shelter insects such as ladybirds.
- Begonias, busy lizzies, pansies, fuchsias, hostas, ferns and many others all enjoy shade or semi-shade, but most plants like either sun or half-sun. Always wait until the possibility of frost has well and truly passed before planting up annuals.