Few garden features repay the effort as generously as a pond. A sunken half-barrel, an old washing-up bowl, or a two-metre hollow in an unloved corner can transform a patch of grass into a place where frogs hunt, dragonflies patrol and hedgehogs stop for a drink. In a small garden, every square metre matters — and a pond is the single most wildlife-rich square metre you can make.

Ponds work because they are rare. Britain has lost the majority of its ponds in the last century, so anything that holds water for most of the year becomes a magnet. You do not need a large garden, a pump or any chemical treatments. You need a suitable spot, the right depth and a handful of native plants.

Choosing the Spot and the Size

Position matters more than size. Aim for somewhere that gets sun for at least half the day, but is not scorched from dawn until dusk — a little shade from a fence or shrub in the afternoon helps keep water temperatures steady and limits algae. Full shade under a tree is the one place to avoid: you will spend years fishing out leaves, and the roots make digging miserable.

As for size, anything from 1 metre by 1.5 metres upward will thrive. A larger pond of 2 by 3 metres will support more species and is less prone to swinging between clear and green, but a small one is far better than none. Make sure at least one side is easy to reach for maintenance, and leave a wild strip nearby — long grass, a log pile, some leaf litter — so creatures have somewhere to shelter when they leave the water.

Getting the Depth Right

Depth is where most small ponds go wrong. Too shallow, and the water boils in summer and freezes solid in winter, killing anything overwintering in the mud.

A good profile for a British garden pond looks like this:

• A shallow beach: 5 centimetres deep or so, sloping gently, so hedgehogs, birds, bees and amphibians can walk in and out without drowning.
• Planting shelves: 20 to 30 centimetres deep, ideally in two tiers, for marginal plants and for frogs to sit and warm up.
• A central sump: 60 to 75 centimetres at the deepest point — enough to stay liquid beneath the ice and give frogs somewhere to spend the winter.

For the liner, butyl rubber is the most durable and forgiving if you want a flexible shape. A rigid preformed liner is simpler for a very small garden. Either way, line the hole with sand and an old piece of carpet or underlay before you lay it, and leave the edges overlapping so you can tuck them under turf or paving stones. Rainwater from a butt is ideal for filling; tap water will do, but let it stand for a few days before adding plants.

Planting for Wildlife, Not Just Looks

Native plants support far more insects than exotic ones, and insects feed everything else. Aim for a mix of three groups.

• Oxygenators, such as hornwort and water starwort, live below the surface and keep the water clear.
• Marginals for the shelves — marsh marigold, water mint, ragged robin, soft rush and purple loosestrife all earn their place, though yellow flag iris can be thuggish in a tiny pond.
• Floating and surface plants — a small water lily, frogbit or water soldier — shade the water and give damselflies somewhere to lay.

Never plant floating pennywort, New Zealand pigmyweed, parrot's feather or water fern. These are invasive non-native species, illegal to plant in the wild, and they will smother a small pond within a season. Ask at a reputable nursery for native stock, and don't take plants from a wild pond.

Safety, Escape Routes and Fish

If young children use the garden, a pond is a genuine hazard. Options include a raised pond with a firm, high edge; a sturdy rigid grid fixed just below the surface; or a fence with a lockable gate around the water. Always supervise small children near water, whatever is in place.

For wildlife, the priority is escape. Hedgehogs, voles and fledgling birds drown in steep-sided ponds, so build at least one gradual ramp — a plank wrapped in chicken wire, a stack of stones or a gently sloping end.

Resist the temptation to add fish. Goldfish and even small native fish eat tadpoles, dragonfly larvae and everything else you are trying to attract. A wildlife pond is better without them, and without a pump or filter too.

Looking After It Through the Year

Let the pond find its own balance for the first year. A green flush of algae is normal while plants establish. If blanketweed becomes a nuisance, twirl it out with a stick rather than reaching for chemicals, and leave it on the edge for a day so anything caught can crawl back.

In autumn, net out some falling leaves — but not all, and not every day. In winter, do not clear the pond. Frogs and newts hibernate in the mud, and insects shelter in hollow plant stems, so leave the dead growth standing until late spring. Top up with rainwater when levels drop, and resist the urge to introduce frogspawn from elsewhere; amphibians will find a well-made pond within a year or two, and moving spawn around spreads disease.

Leave the pond alone and it will do the rest. Sit quietly at dusk in May and you will hear the payoff: a chorus of croaks, the rustle of a hedgehog at the edge, and the first dragonfly of the year drying its wings on a warm stone.