Why a small pond is the best thing you can add

If you do only one thing for wildlife this year, make it a pond. Even a modest one — a metre across, tucked into a corner of a courtyard or beside a patio — becomes a magnet for creatures that cannot use the rest of your garden. Frogs and newts need water to breed. Dragonflies and damselflies spend the first year or two of their lives underwater as larvae, then hunt over the surface as adults. Birds visit to drink and bathe, hedgehogs stop for a drink on a dry night, and bats will sweep in at dusk for the insects gathering above the water. A pond is not an ornament; it is a habitat, and you can build one in a weekend.

Choosing the right spot

Position matters more than size, so take a few minutes to think before you dig.

• Sunlight: aim for four to six hours a day. Warm shallows mean more insect life, which means more food for everything else.
• Keep clear of trees and hedges: fallen leaves rot and feed algae, and roots can puncture a liner. You will also spend less time fishing leaves out.
• Level ground: a liner pond needs a level rim all the way round, or you will end up with a very visible sloping tideline.
• Near the house: you will enjoy it more, and it is safer if there are small children about.
• Close to a source of rainwater: siting it within reach of a water butt or downpipe makes topping up with rainwater far easier. Tap water contains nutrients that encourage algae.

Building it: size, depth and edges

For a small garden, a pond of about 1.5 metres by 1 metre is plenty. Make it deeper than you might expect — 60–75cm at the centre, which gives frogs and newts somewhere to shelter through winter and stops the pond freezing solid in a cold snap. Include at least one shallow shelf, some 20–30cm deep, for planting and for birds to stand in while they bathe.

A butyl or EPDM liner is the most flexible option and will last decades. Line the hole with old carpet, cardboard or purpose-made underlay first, then smooth the liner carefully into place and tuck the edges under turf or paving. Preformed rigid ponds are quicker, but choose one with gently sloping sides rather than steep walls. Whichever you use, allow wildlife to get in and out: a gently sloping edge, a few large stones half-submerged, or a rough plank resting in the water gives hedgehogs, frogs and beetles a way out. Hedgehogs can swim but cannot climb steep sides, and they drown in tidy ponds.

Fill the pond with rainwater if you possibly can, then leave it to settle for two to four weeks before planting. It will look alarmingly green at first — this is normal. Resist the urge to empty it. Avoid fish entirely: goldfish and koi eat frogspawn, tadpoles and dragonfly larvae, and their waste feeds algae.

Planting it with British natives

A good pond has a mix of plants at different depths, and roughly a third to a half of the surface shaded by floating leaves — enough to keep the water cool and give dragonflies somewhere to perch, while leaving open water for birds.

• Oxygenators, grown submerged in baskets: hornwort, spiked water-milfoil and water starwort.
• Marginals, on the shallow shelf: marsh marigold, water forget-me-not, water mint, purple loosestrife and, if you have room, yellow flag iris.
• Floating plants: native frogbit is ideal for a small pond. A water lily will need a large pond, so choose a pygmy variety if you long for one.

Plant into aquatic baskets using low-nutrient aquatic compost, topped with gravel or hessian. Ordinary garden soil or potting compost will leach nutrients and turn the water green. Never plant invasive non-natives such as New Zealand pygmyweed, floating pennywort, water fern or parrot's feather. They are illegal to plant in the wild and will smother a small pond within a season.

What will turn up — and how to help it

Frogs usually arrive first, spawning in February or March. Smooth and palmate newts may follow, along with damselflies and dragonflies whose larvae will spend one or two years in the water before emerging up a plant stem. Leave rough grass, a stone pile and a small log stack near the pond for amphibians and hedgehogs to shelter in.

Do not be tempted to move frogspawn or adults in from elsewhere. Amphibians carry diseases, including ranavirus and chytrid fungus, and introduced spawn can devastate a local population. If your pond is right, wildlife will find it. Keep slug pellets and other garden chemicals away from the area entirely — they are lethal to the creatures you are trying to attract.

Looking after it through the year

Maintenance should be light and gentle. In spring, clear a little blanketweed by hand, twisting it onto a stick, and cut back any dead stems — leave them on the pond edge for a day so that small creatures can crawl back into the water. Through summer, top up with rainwater in dry spells and thin duckweed if it spreads, but never strip a pond bare.

In autumn, net out fallen leaves before they sink, though leave a few for overwintering insects. Most importantly, do not tidy the pond in winter. Frogs and newts overwinter in the silt at the bottom and in leaf litter around the margins. If silt builds up over several years, remove only a bucketful in early spring, and leave it beside the pond for a few days so that anything living can return. Do it gently, and your tiny pond will reward you for years.