Why a small pond is worth the space

Of all the things you can add to an urban garden, water gives the quickest return. A pond the size of a dining table — roughly 1.5 metres by 1 metre — will pull in common frogs and smooth newts within a season, and once there is open water to patrol you will see damselflies and dragonflies hunting over it on warm afternoons. Birds use the shallow edges to bathe and drink, hedgehogs come down for a sip at dusk, and the insects bred in the water feed nestlings in the hedge behind. It need not be large, deep or expensive, only safe, well sited and left to find its own balance.

Choosing the right spot

Sunlight and shelter matter more than the view from the kitchen window. Aim for five or six hours of sun a day: that warms the water, feeds the plants and encourages dragonflies.

• Keep clear of deciduous trees. Fallen leaves are the main cause of green, soupy water. A few metres from a hedge is fine, but not directly beneath a tree.
• Avoid low spots and runoff. Water draining off the lawn carries fertiliser and weedkiller, both of which feed algae.
• Consider a raised pond if you have small children, poor drainage or heavy clay. A raised edge means less digging and gives you somewhere to sit and watch.
• Leave an escape route. One edge should be very shallow — a pebble beach or a sloping ramp of stones — so frogs, newts, hedgehogs and drowning bees can all climb out.

If there are toddlers about, fit a rigid mesh cover or fence the pond, and never make the water deeper than 60 centimetres. A shallow, well-planted pond is safer and every bit as good for wildlife.

Digging, lining and filling

Make the hole irregular rather than square, with one side shallow and one side deeper. A good profile for a small pond is a shelf around 20 centimetres below the finished water level for marginal plants, sloping down to a central area 45–60 centimetres deep. That is enough for frogs to overwinter and for dragonfly larvae to survive a hard frost, without being more than you need.

Use butyl liner over a layer of old carpet or purpose-made fleece underlay. It is cheaper than a preformed shell and far more adaptable. Bury the edges so the liner disappears under turf, gravel or paving, and leave an overhang of a few centimetres where rainwater and wildlife can get in.

Fill with rainwater from a water butt rather than the tap. Tap water carries chlorine and nutrients that give algae a head start. If you must top up from the mains, let the water stand in a can for a day or two first, and do it little and often.

Planting the edges and shallows

Native planting is what makes a pond work. Use baskets of ordinary garden soil — not compost, which is far too rich — topped with gravel, and set them on the shelf so the rims sit just below the surface.

• Marginals: marsh marigold, water mint, water forget-me-not, ragged robin, lesser spearwort, soft rush and sedges. These give cover for emerging dragonflies and egg-laying sites for newts.
• Oxygenators: hornwort and water starwort. They keep the water clear, shelter tadpoles and need thinning only once a year.
• Deep water: a small water lily or bogbean, if the pond is at least 60 centimetres deep.
• Around the edge: long grass, a log pile and a few flat stones. Damp shade is where frogs and newts spend most of the year.

Buy from a reputable aquatic nursery and never take plants or spawn from the wild or from another pond — that is how invasive species spread. Avoid floating pennywort, New Zealand pygmyweed, parrot's feather and water fern at all costs, and skip fish entirely. Fish eat tadpoles and stir up nutrients; a fish-free pond is clearer, richer and far less work.

Keeping the water clear

Green water in a new pond is normal, and usually settles once plants establish and predators arrive. To help it along:

• Net out fallen leaves in autumn before they rot.
• Never use fertiliser, insecticide or weedkiller nearby, and do not feed the pond.
• Add a small mesh bag of barley straw in spring to discourage blanketweed.
• Thin oxygenators in late summer, leaving a rake's worth on the edge for a day so any trapped creatures can crawl back.
• Keep roughly a third of the surface as open water — crowded ponds grow stagnant.

Seasonal notes from the pond edge

Late winter and early spring bring the first frogspawn, often in the last week of February in mild towns. Newts arrive soon after, laying eggs singly in folded leaves. Watch marsh marigold open, and the first damselflies hatch by May.

Summer is the pond's loudest moment: common darters and emperors hunting over open water, blackbirds and starlings splashing in the shallows, bats taking midges at dusk. Keep the level topped up with rainwater in dry spells, because a pond that dries out in July loses a whole year's breeding.

Autumn is for maintenance, not tidying. Clear the leaves, but leave marginal stems standing and the log pile alone — dragonfly larvae climb those stems to emerge. Winter is for restraint: if the pond freezes, do not smash the ice, as the shock can kill overwintering frogs. Float a ball, or stand a pan of hot water on the surface, to melt a hole for gases to escape. Then leave it be. Most of the life in your pond is hidden in the mud, the leaf litter and the damp corners around it, waiting for the lengthening days.