Finding the Right Spot Among the Trees

A small pond is the single most valuable thing you can add to a piece of woodland. It costs a weekend's digging and a length of liner, and within a season it will be pulling in frogs, dragonflies, bats and thirsty birds from far beyond your boundary. But digging in a wood is a different business from digging in a garden. The trees dictate light, leaf fall, root run and how much debris arrives every October.

Aim for a clearing, a ride edge or a gap on the south side of the stand, where the water gets at least four to six hours of direct sun. Site it five or six metres clear of mature trunks. Willow, poplar and sycamore push out water-hungry roots that will find a liner, and a pond under a full canopy fills with leaves that rot down and starve the water of oxygen. If you must work beneath trees, choose the shallowest hollow you can and plan to rake. Avoid the bottom of a slope, where run-off carries silt and leaf litter straight in.

Shape, Size and the Dig

Two metres by one and a half is plenty; bigger is better, but don't overreach on the first attempt. Mark the outline with string and canes, then cut and stack the turf grassy-side down. It makes excellent backfill and a nursery for invertebrates.

Dig a shallow shelf, about 30cm wide at 20–25cm deep, right around most of the perimeter, then drop to a basin of 60–75cm in the middle. Those shelves let you plant marginals and give amphibians and hedgehogs a safe way in and out. Slope one side gently rather than cutting a cliff, so anything that tumbles in can climb out. As you dig, pull out roots and sharp stones. If you meet a root thicker than your wrist, work around it; cutting through it can destabilise a mature tree. Check the waterline with a plank and a spirit level before you go any further.

Lining and Filling

One-millimetre butyl rubber is the standard for good reason: flexible, tough and long-lived. Allow roughly 3.5m by 3m for a two-metre pond, giving you 30cm of overhang all round. Buy underlay as well — geotextile or old jute-backed carpet with the foam stripped off — and cover the whole hole, especially where stones remain.

Drape the liner in loosely and let it settle as it fills; never stretch it. Rainwater from a butt is ideal. Tap water works at a pinch but carries chlorine, so let it stand for a few days first and top up slowly at low flow, playing the hose onto a stone so it doesn't disturb the silt. Once full, fold the overhang neatly and bury it under soil and turf, leaving one edge as a shallow beach of gravel for birds and amphibians.

Do not add fish. In a small woodland pond they will clear out the tadpoles, newt larvae and dragonfly nymphs you are trying to encourage.

Planting for Native Wildlife

Plants do the real work: oxygen, cover and egg-laying sites. Aim for around a third of the surface covered, keeping some open water in the middle.

• Marginals for the shelf: marsh marigold, water forget-me-not, brooklime, ragged robin, lesser spearwort and yellow flag iris, which is best kept in a basket as it spreads readily.
• Oxygenators: hornwort, water starwort and curled pondweed, dropped in as lead-weighted bunches.
• Floating: frogbit, or a compact water lily if you have the depth.
• Bankside: foxglove, red campion and wood anemone planted into the spoil in dappled shade.

Use peat-free aquatic compost, and avoid invasive non-natives such as parrot's feather, water fern and New Zealand pigmyweed. They are a nightmare to remove once established. Never take plants from the wild.

Welcoming Frogs, Dragonflies and Birds

Frogs usually arrive within a season, often before the plants have settled in. Newts and dragonflies take longer, but they come. Dragonflies and damselflies need sun to emerge, so keep part of the water open and leave vertical stems around the edge — iris and rush are used as emergence posts, and the empty nymph cases you find there are proof the pond is working. Bats will drink on the wing at dusk.

Stack a few logs and stones at the margin, half in and half out of the water, and leave tussocky grass uncut along one bank. That rough edge is where amphibians shelter over winter.

Looking After It Through the Year

Autumn is the busy season. Stretch a net over part of the pond during leaf fall, or rake twice a week and stack the weed on the bank for a day so anything living can crawl back. Thin excess weed in late summer rather than spring.

Never clean the pond out in spring, when tadpoles and larvae are at their most vulnerable. If it silts up badly, clear half in September and the other half the following year. All amphibians are protected from sale in the UK, and great crested newts are fully protected — if you find one, stop work and take advice from the statutory conservation body for your part of the country.

Don't panic if the water turns green in the first few weeks. It settles once the plants and invertebrates find their balance. Dig it, plant it, then leave it largely alone, and the wood will do the rest.