Why a pond is the best wildlife investment on a smallholding

Of all the things you can do for wildlife on a smallholding, a pond gives the biggest return for the least ground. A pool two metres across will pull in common frogs, smooth newts, diving beetles, water boatmen and pond skaters within a single season, and by the second summer you can reasonably expect damselflies and the first dragonflies. Birds use ponds constantly — blackbirds and sparrows bathing, swallows gathering mud for nests, bats hunting the midges that rise off the surface at dusk. There is a practical dividend too: frogs and toads work the kitchen garden all summer, taking slugs, beetles and leatherjackets by the barrowload. And a pond gives you somewhere to stand with a mug of tea at the end of a long day, which is worth more than most of us admit.

Siting the pond: light, land and common sense

Aim for at least half a day of direct sun; a pond in deep shade stays cold, grows little and supports far less. Avoid overhanging trees, partly for the leaf fall that feeds algae, but mainly because roots can puncture a liner years down the line. Keep away from cultivated ground that receives slurry, fertiliser or weedkiller — nutrient-rich run-off means blanketweed all summer and no clarity. Choose ground that is reasonably level, and put the pond where you can see it from a window or a path, so you notice problems early and actually watch the wildlife. If children visit, plan a shallow edge rather than a cliff.

Digging and lining: shallow shelves beat steep drops

• Mark an irregular, curvy outline — it looks natural and gives far more edge habitat per square metre.
• Dig a marginal shelf 20–30 cm deep and 30–45 cm wide around at least part of the perimeter.
• Include one gently sloping beach, roughly a 1 in 4 gradient, so hedgehogs, frogs and birds can walk in and climb out. A few flat stones help.
• Take the centre down to 60–75 cm. In the UK that is deep enough to stay unfrozen below most frosts and gives amphibians somewhere to overwinter. Deeper is unnecessary and awkward to manage.
• Line with butyl rubber of 1 mm or thicker, over a polyester fleece underlay and a couple of centimetres of soft sand. Allow 30 cm of overlap all round and bury the edge under turf or stone.

Dig in spring or early autumn, when the soil is workable and amphibians are not mid-breeding. If you are near known ponds where great crested newts may be present, check before you lift a spade — they are strictly protected, and it is far easier to move a plan than to undo a problem.

Filling and establishing without a green soup

Fill with rainwater from a butt or a downpipe where you possibly can. Tap water will do at a pinch, but it carries chlorine and often phosphates and nitrates that feed algae. Expect the water to look like pea soup in the first spring and summer, then clear as plants and microscopic life find their balance. Do not empty it and do not reach for chemicals. A net of barley straw or a bundle of oxygenating weed helps in the meantime. Keep fish out: goldfish and koi eat tadpoles and newt larvae, and they foul the water badly.

Planting natives for shelter, cover and clean water

Plant British natives in aquatic baskets of heavy loam — never potting compost or fertiliser, which leaches and fuels algae. Aim to cover roughly a third to a half of the surface with floating leaves: enough shade to keep algae in check, with open water left for drinking and bathing.

• Marginals: marsh marigold, water mint, ragged robin, lesser spearwort, bogbean and purple loosestrife for the damp edge.
• Emergents: yellow flag iris is lovely but thuggish — keep it in a basket and divide hard.
• Oxygenators: hornwort, curled pondweed and water starwort, submerged workhorses that shelter tadpoles.
• Floating: frogbit, plus a native water lily if you have the room, basketed with a metre to spread.
• Avoid: floating pennywort, parrot's feather, New Zealand pigmyweed, water fern and water soldier. These are invasive and never belong in a garden pond — and never tip out an aquarium.

Leave one bank of grass long, plant knapweed and field scabious along the rim, and stack a few logs nearby. Dense cover around the edge is what persuades amphibians to stay.

Managing the pond through the year

Ponds need less work than people think. Clear some autumn leaves but leave a few in the bottom, and in late summer thin oxygenators and marginals with a rake — never more than a third at a time — stacking the debris on the bank for a day so anything living can crawl back.

• Never use fertiliser, herbicide or insecticide near the edge; even a small drift knocks back the invertebrates that feed everything else.
• In winter, float a ball or stand a pan of hot water on the surface to keep a patch open. Never smash the ice — the shock can kill hibernating frogs and newts.
• Top up with rainwater in dry spells, and leave stones and cover at the margins if herons visit.
• Resist tidying. A slightly scruffy pond, with leaf litter below and long grass around, holds far more life than a manicured one.

Then be patient. In a country garden the frogs usually find you first, often within weeks of filling. Newts and dragonflies take longer, sometimes two or three seasons, but they come. Sit quietly at the edge on a warm June evening and you will hear the whole thing working.