Expert advice from 'Gardening Which?' by Rosemary Ward
If there's such a thing as a magic bullet for a wildlife garden, it's a wildlife pond. Almost from the instant it's created it will attract new creatures - and make an excellent spot for wildlife-watching. Ponds in gardens have become increasingly crucial as countryside ponds fall victim to intensive farming and development.
Many creatures live in ponds all year round, including diving beetles, water spiders, pond snails and small fish such as sticklebacks. Many species also spend part of their life cycle under water - not only tadpoles, but the larvae of insects including spectacular dragonflies.
Ponds also support midges and mosquitoes, which we may not enjoy, but which provide an important food source for bats, and for birds such as swallows and swifts. Other birds and mammals will also be attracted to the pond for drinking and bathing.
Creating a wildlife pond
* Choose a site that is level and sheltered, has sun for at least two-thirds of the day, is not under trees and does not get waterlogged.In schools, make sure the site will not get too much disturbance but is not too isolated and can be made safe - talk to your health and safety adviser.
* Your pond should, ideally, have an area of 10 square metres or more, have gently sloping sides and be at least 60cm deep in part to ensure it never freezes completely. Think about what you will do with the excavated soil.
* Butyl rubber, about pound;5 a square metre, is the best liner. You need to protect it by removing any visible stones from the hole and covering the soil with a 2cm layer of sand, old carpet, wet cardboard or newspaper.
* Choose local native wildflowers, which are easy to manage if you grow them in submerged plastic baskets (available from garden centres). You need a mix of floaters such as amphibious bistort and frogbit; submerged oxygenators such as water milfoil and water starwort; emergers which are half in and half out of the water, such as flag iris, flowering rush and water forget-me-not; and marginals for boggy edges such as marsh marigold, brooklime and water mint.
* Some aquatic plants are best avoided. A few imported varieties can be highly invasive and damaging to natural water courses. The worst offenders are New Zealand pigmy weed (also sold as Australian swamp stonecrop, Crassula helmsii, C. recurva), Parrot's feather (also sold as Myriophyllum aquaticum, M. brasiliense and M. proserpinacoides) and floating pennywort (Hydrocotyle ranunculoides). Also avoid other non-natives such as fairy fern (Azolla filiculoides), small-leaved duckweed (Lemna minuta), and Canadian pondweed (Elodea canadensis). Many native plants, such as white and yellow water lilies, greater reed mace or bulrush, common reed and greater spearwort, are also unsuitable for most ponds as they are too large and vigorous and can soon overwhelm them.
* A paved area next to the pond gives good year-round access for pond-watching, a gravel "beach" allows birds and adult amphibians to reach the water easily, and blundering hedgehogs to escape. Long grass provides shelter for young amphibians, while shrubs should be restricted to the north side, where they will provide shelter without shade. A bog garden, made by extending the liner over a water-retaining lip, gives more scope for attractive plants.
* Tap water is fine for filling your pond but clear, fresh rain water is better. When the pond is finished, add a bucket of water and sludge from an existing garden pond to help introduce insects and smaller creatures. Do not add ornamental fish as they eat a lot of tadpoles and insect larvae, and can make the water murky. It's also best not to introduce amphibians artificially - if the pond is suitable, they will find it.