A small pond is the best thing you can add

If you have room for a shed, you have room for a pond. Even a modest one — say 1.5 metres by 1 metre — will do more for garden wildlife than a border of bee-friendly flowers twice the size. British gardens have lost a great many ponds over the past fifty years, so every new one matters. Frogs, toads, newts, dragonflies, damselflies, water beetles, bats and thirsty birds all find a small pond surprisingly quickly.

The key is to make the edges gently sloping rather than vertical. A pond with shallow water where birds can bathe and amphibians can climb in and out is worth far more than a deep, steep-sided one. Water quality also matters, so plan to fill your pond with rainwater collected from a butt or a downpipe.

Choosing the spot and getting the shape right

Pick a spot that gets sun for at least half the day. Warmth encourages the insects that dragonflies and bats feed on, and helps your plants grow away strongly. Avoid the drip line beneath large deciduous trees, which will fill your pond with leaves and roots, and keep away from the foot of a fence you might one day want to replace. Ground that is naturally boggy and low-lying is ideal.

Mark out a shape with a hose — a curved, irregular outline always looks more natural than a rectangle — then dig down in stages:

• A shallow ledge about 10cm deep and 25cm wide around part of the perimeter, for birds and hedgehogs to stand in.
• A marginal shelf 20–30cm deep, wide enough to hold two or three planting baskets.
• A central area 60–75cm deep, which stays frost-free at the bottom and gives amphibians somewhere to overwinter.

Vary the depth across the pond rather than digging a perfect bowl. Check the rim is level using a plank and a spirit level, and rake the sides so they slope gently rather than dropping away like cliffs.

Lining, filling and finishing the edges

Remove any sharp stones, then lay a 2–3cm bed of soft sand, followed by old carpet, underlay or a proper geotextile fleece. A butyl liner will last decades; a cheaper flexible liner will do for a first attempt. Unroll it loosely into the hole, weight the edges with bricks, and begin filling slowly with rainwater. As the water rises, the liner will settle into the contours, and you can pleat the corners neatly by hand.

Once full, trim the liner leaving a generous 30cm overlap, and tuck it under turf or hide it with flat stones, gravel and creeping plants. Leave the water level roughly 5–8cm below the rim so that frogs and hedgehogs do not find themselves trapped. For anything steeper than a gentle slope, build a small escape ramp from stones, a piece of weathered wood or a length of rough rope pegged into the bank.

Planting with natives, not ornamentals

Native plants support native insects, and most British pond wildlife evolved alongside them. Aim for roughly a third of the surface covered with floating or submerged foliage by midsummer — enough to shelter tadpoles, but not so much that the water stagnates.

• Oxygenators: hornwort, water starwort or curled pondweed, planted in baskets of loam.
• Marginals for the shelf: water forget-me-not, marsh marigold, lesser spearwort, water mint, ragged robin and soft rush.
• Edge and damp-ground plants: lady's smock, purple loosestrife and marsh woundwort, which pollinators adore.

Use loam or a low-nutrient aquatic compost, never garden soil or anything enriched, and top each basket with gravel so the compost stays put. Do not plant yellow flag iris or floating pennywort in a small pond — both will take over, and some invasive water plants are illegal to allow to spread into the wild. Skip fish entirely: they eat tadpoles, insect larvae and the small creatures that make a pond interesting.

Letting wildlife arrive on its own

The best approach is patience. Frogs and newts will find the pond themselves, usually within a season. Moving spawn or plants between ponds risks spreading disease and can be illegal, so please don't. Dragonflies often appear within weeks, and birds will find the shallow ledge almost immediately if you leave a few stones and a stick or two breaking the surface.

Pile a few logs and some leaf litter nearby, and leave a patch of longer grass at one end. That combination of pond, damp cover and undisturbed corners is what turns a puddle into a habitat.

Looking after it through the year

Ponds need less work than a lawn. In spring, top up with rainwater and thin out any blanketweed by hand — leave it on the bank for a day so anything caught in it can crawl back. In late summer, divide congested marginal baskets so plants do not crowd the water. In autumn, resist the urge to tidy up; seed heads feed birds, and the stems provide overwintering homes for insects. If leaves are a problem, stretch netting above the surface rather than letting it touch the water, and remove it once the trees are bare. Never use tap water, fertiliser or chemical treatments. A pond left mostly to itself will reward you for years.