Creating a garden pond for amphibians

Why a garden pond is one of the best things you can build for wildlife

Few garden projects repay you as richly as a pond. In a country where roughly half of our ponds were lost during the twentieth century, the modest puddle at the end of your lawn has become genuinely important habitat. Common frogs, common toads, smooth and palmate newts will all find it, often within a season or two of it filling. Add dragonflies and damselflies, water beetles, pond skaters and a cast of birds coming down to bathe, and you have a patch of water that is busier than most nature reserves.

The good news is that amphibians are not fussy about style. They do not care whether your pond is a butyl-lined rectangle or a sculpted wildlife pool. They care about depth, shelter, clean water and somewhere to climb out. Get those four things right and the rest is decoration.

Choosing the site

Aim for somewhere that gets sun for at least half the day. Warm water means more insect life, and dragonflies in particular will not bother with a pond in deep shade. Complete shade also slows plant growth and keeps the water cold and lifeless.

Keep it away from large deciduous trees. Falling leaves rot down and feed algae, and roots can puncture a liner from below. If you have no choice, a pond net in autumn saves a lot of grief later. Avoid the lowest point of the garden if the ground is heavy clay, unless you actually want a bog. And think about access: you will be standing at the edge with a rake and a bucket more often than you expect.

Getting the shape and depth right

The single most common mistake is making a pond too shallow. A puddle that dries out in July will not raise a generation of tadpoles.

• Overall size: 2 metres by 2 metres is a sensible minimum. Bigger is easier to keep balanced, not harder.
• Depth: 60 centimetres at the deepest point as an absolute minimum, and 90 centimetres to a metre if you can manage it. That keeps a layer of water below the frost line where frogs and newts can overwinter in the mud.
• Planting shelves: leave one or two ledges around 20 to 30 centimetres deep for marginal plants and for frogs to sit on. A shelf 45 centimetres down suits water lilies.
• A gentle beach: slope one end gradually rather than dropping sheer. Hedgehogs, fledglings and frogs all drown in steep-sided ponds. A shallow ramp of stones or a piece of roughened timber leaning into the water solves it.
• Varying the outline: wavy edges with a bay or two give shelter from wind and create different micro-habitats. It also looks far more natural than a perfect oval.

Use a butyl or EPDM liner with a fleece underlay, and leave a generous overlap around the edge before you bury it under turf or gravel. A 15 to 20 centimetre rim of flat stones makes a tidy edge and gives amphibians somewhere to haul themselves out.

Planting it up

Plants do the heavy lifting: they shade the water, absorb nutrients and give wildlife cover. Use peat-free aquatic compost and native species wherever possible.

• Oxygenators: hornwort, water starwort or water milfoil, planted in baskets on the shelves. These compete with algae and shelter tadpoles.
• Marginals: marsh marigold, water forget-me-not, water mint, lesser spearwort and soft rush. Water mint is a magnet for bees and hoverflies.
• Floating and deep-water: a native water lily if the pond gets decent sun. Its leaves provide shade and somewhere for adult frogs to lurk.
• What to avoid: floating pennywort, New Zealand pygmyweed, water fern and parrot's feather. These are invasive non-native species and are illegal to plant in the wild. Never tip pond plants into a stream or canal.

Fill baskets in late spring and top them with gravel so the compost does not cloud the water.

Filling and letting it settle

Rainwater from a butt is ideal. Tap water works at a pinch, but it carries nutrients that feed algae, so if you must use it, fill once and then never again. Do not add fish. Goldfish and koi will eat spawn, tadpoles and newt larvae, and they turn clear water green. You also do not need a pump or filter in a well-planted pond; wildlife ponds are meant to be still.

Expect the water to go green for a few weeks while it finds its balance. Leave it alone, get the plants growing, and it will usually clear by itself. Thread-like blanketweed can be twirled out with a stick.

Looking after it through the year

• Autumn: rake out fallen leaves, but leave them on the edge for a day so any creatures can crawl back.
• Late winter: cut back dead stems above the water, and clear a little duckweed. Never empty and scrub the pond; that destroys everything living in the silt.
• Spring: watch for frogspawn in jelly clumps from February, toadspawn in strings a little later, and newt eggs wrapped singly in folded leaves. Keep cats indoors at dawn if you can.
• All year: avoid slug pellets, weedkillers and insecticides anywhere near the pond, and check long grass before strimming.

Never move spawn or amphibians between ponds; disease spread is a real threat to British populations. Great crested newts are protected by law, so if you are lucky enough to find one, enjoy it from a distance and record it rather than interfering. Then put the kettle on and watch.