A pond is the best value wildlife feature you can add

Even a pond no bigger than a dining table will pull in more species than a garden twice the size planted entirely with wildflowers. Water is scarce in the British landscape, and anything that holds it for more than a few weeks becomes a magnet. In a small urban garden, a pond turns a patch of grass into a genuine oasis: frogs in February, damselflies in June, sparrows splashing at dawn, hedgehogs drinking quietly after dark.

You do not need a big garden, a liner, or any particular skill. You need a watertight container, some rainwater, a handful of native plants, and the patience to leave it alone.

Choosing the spot

Aim for half sun, half shade. A pond in full sun all day will be green with algae by June; one in deep shade beneath a tree will be cold, lifeless, and clogged with fallen leaves. Four to six hours of sun a day, with dappled shade in the afternoon, suits most pond life well.

Keep it away from overhanging trees and away from the lowest point of the garden if that corner floods. Above all, put it where you can see it from a window or from the kitchen door. You will learn far more about the wildlife in your garden from a pond you glance at ten times a day than from one you visit once a week.

An irregular shape with gently sloping sides beats a neat circle. For depth, 45–60cm in the centre is enough for frogs to overwinter in the silt; 75cm if you can manage it means the pond is far less likely to freeze solid.

Building it: liner, barrel or buried tub

• A butyl liner gives you the most freedom of shape. Dig the hole with a shallow 20cm shelf around the edge for marginal plants, then a deeper centre. Line it with old carpet, sand, or damp newspaper to protect the rubber.
• A half barrel or large tub is ideal for a courtyard or balcony. Choose one at least 60cm across; anything smaller warms up and dries out too quickly to be stable.
• An old sink, a glazed pot, or a large trug will all work if it holds water. Place it on a level, firm base so it does not tip.

Fill it with rainwater from a butt where you can. Tap water is fine if you leave it to stand for a few days so the chlorine dissipates, but rainwater is better and free.

Then make a way out. A piece of weathered wood, a pile of stones, or a gently sloping edge lets frogs, hedgehogs and beetles climb out. Steep-sided containers are death traps for anything that falls in.

Planting it up

Wait a fortnight before planting so the water settles and warms. Use native plants, and buy them from a reputable aquatic nursery. Do not import plants, water or frogspawn from a wild pond or a friend's — that is exactly how invasive species and amphibian diseases spread.

• Oxygenators: hornwort and water starwort, dropped in loose rather than potted.
• Marginals: water forget-me-not, marsh marigold, water mint, lesser spearwort, ragged robin. Yellow flag iris is handsome but vigorous, so it needs a big pond.
• Floating: frogbit, or one small water lily. Keep floating leaves to about a third of the surface and no more, or the water goes stale.

Plant in baskets of loam-based compost topped with gravel. Avoid ordinary garden soil — it is too rich and will feed a blanket of algae. Never plant New Zealand pygmyweed, water fern, floating pennywort or parrot's feather; all four are banned in the UK for good reason.

What to expect, and when

The first spring is always the most surprising. Water boatmen, pond skaters and daphnia appear as if from nowhere, because they fly in. Algae will bloom. Leave it: by midsummer, as the plants establish, the water generally clears on its own.

• February to March: frogs arrive and spawn. Never move spawn between ponds.
• Spring: tadpoles hatch. Newts may find you, though sometimes it takes years.
• May to August: damselflies and dragonflies. Their larvae live underwater for a year or two before emerging.
• All year: birds bathe and drink — blackbirds, sparrows, starlings — and hedgehogs visit at dusk.

Resist fish. Even two goldfish will clear out tadpoles and dragonfly larvae within weeks.

Looking after it through the year

Little and often is the rule. Top up in dry spells with rainwater. Thin oxygenators in late summer with a rake, but leave the pile on the pond edge overnight so anything caught up can crawl back.

A proper clean-out should happen every five to seven years at most, in September or early October — never in spring, when amphibians and insects are overwintering in the silt. Keep a bucket of pondwater to hold creatures while you work.

Never use chemicals, fertiliser or weedkiller anywhere near the pond, and leave dead stems standing over winter rather than cutting everything back. If the surface freezes, float a ball to keep a small hole open for gas exchange, and never smash the ice — the shock can kill what is below.

Mostly, though, the answer is to do nothing. Ponds that are left slightly untidy, with a bit of leaf litter and a few stones at the edge, are the ones that teem.