A modest puddle that pays you back

You do not need an acre and a digger to keep a wildlife pond. A hole a metre across, with one deep corner and one shallow shelf, will draw in more life than almost anything else you can do in a small garden. Frogs will find it. Smooth and palmate newts will find it. Within two summers you should have damselflies drying their wings on a reed stem and dragonflies quartering the garden like little hawkers. A pond is not a feature you look at so much as a small machine for turning sunlight and insects into amphibians, and it works best when you leave it largely alone.

Siting and shaping the hole

Pick a spot that gets sun for at least half the day, but not one where it bakes all afternoon. Partial shade from a hedge or fence reduces the summer algae and gives frogs somewhere damp to sit. Keep it away from the drips of a large tree, particularly willow or poplar, whose roots will happily push through a liner in search of the water.

The shape matters more than the size. Aim for:

• A central depth of 60–75cm, deep enough to stay unfrozen at the bottom through a hard winter.
• A shallow shelf 20–30cm deep on at least one side, where marginal plants and frogspawn will sit.
• At least one gently sloping edge, a beach of turf or gravel, so that hedgehogs, fledglings and amphibians can climb out. A frog that cannot get out of your pond is a frog you have killed.

Before you dig, lay a rope on the grass in the outline you want and leave it a day. A curve looks far more natural than a rectangle, and it costs nothing to change your mind at this stage.

Lining, filling and edging

Butyl rubber is the most forgiving liner for a small garden pond and will last decades. Dig out the shelf and the deep section, then line the whole hole with a 5cm layer of soft sand or old carpet to save the liner from stones. Leave plenty of overhang. Fill the pond with rainwater from a water butt if you can, since tap water carries nutrients and chlorine. If you must use mains water, let it stand in the sun for a few days in buckets before you tip it in.

Edge the finished pond with turf folded over the liner, or with flat stones laid so they overhang the water. Both conceal the rubber, and the stones double as basking spots. If there are toddlers in the house, either fence the pond or fit a rigid mesh cover just below the surface until they are older. A shallow shelf is safer than a deep hole, but it is not a substitute for supervision.

Native plants that do the work

Plants are your filter, your shade and your habitat. Choose natives, and plant them in baskets of hessian or open plastic so they cannot run riot.

• Oxygenators: hornwort and water crowfoot, both of which keep the water clear and give newts somewhere to lay eggs.
• Marginals: marsh marigold for early yellow flowers, water forget-me-not for the shallow shelf, lesser spearwort and water mint for scent.
• Taller structure: yellow flag iris and flowering rush, which give dragonfly nymphs a ladder to climb when they emerge.
• Floating cover: a small water lily or frogbit. Keep lilies to a modest size in a small pond, or they will smother it.

Leave purple loosestrife and bulrush to bigger ponds; they will overwhelm a metre-wide hole within two years.

A year at the pond

Spring. Frogs arrive first, often in the last week of February, and the spawn appears in gelatinous clumps low in the shallows. Do not move it. Newts return from their winter hiding places under logs and stones. Plant up now, before the water warms and algae gets a head start.

Summer. Damselflies and dragonflies emerge from June. Keep the pond topped up with rainwater during dry spells, and if blanketweed takes hold, twirl it out with a stick rather than reaching for chemicals. A small amount of algae in spring is normal and usually clears as the plants grow.

Autumn. Amphibians leave the water and head for damp cover. Partly net the pond for a fortnight if it sits under trees, then remove the net so wildlife cannot become tangled. Leave fallen leaves in the border, not in the water.

Winter. Never smash ice on a pond; the shock can kill frogs resting below. Float a small pan of hot water on the surface to melt a breathing hole instead.

Keeping it healthy with very little effort

Resist the urge to clean. A wildlife pond is meant to be a little murky and full of leaf litter; that debris is where the larvae live. Do not add fish, which will eat the frogspawn and the invertebrates you are trying to encourage. Do not feed the ducks. Top up with rainwater, cut back dead growth in early spring rather than autumn, and keep a log pile or stone heap within a few metres of the edge for shelter. Then sit back with a mug of tea and let the garden do the rest. Within a season or two, the pond will be the busiest square metre of your patch.