Shade is not the enemy

Most pond guides assume a sunny spot at the bottom of a wide lawn. Most gardens, in reality, have a damp corner behind the shed where the light never quite reaches. If that is what you are working with, take heart: a shaded pond is not a compromise, it is a different sort of habitat, and in some ways an easier one to keep healthy.

Cool water holds more oxygen than warm water, and the reduced light means far less algae and blanketweed. Frogs, toads and newts do not need sunshine on their backs; they need clean, cool water with no fish to eat their young. A pond tucked under a hazel or a mature apple tree can be one of the most productive wildlife features in the garden. What it does require is a little planning around tree roots, leaf fall and plant choice.

Choosing the spot and judging the light

Spend a day watching the corner before you dig. Dappled shade is ideal, and even two or three hours of filtered light will be enough for marsh marigold to flower. Deep, all-day gloom under a dense evergreen will limit your planting, but the pond will still attract frogs and insects.

• Avoid sitting directly under sycamore, willow, poplar or large oaks. They drop heavy loads of leaf, seed and honeydew, and their roots are thirsty and invasive.
• If you must go under a big tree, consider a part-raised pond or a large container pond rather than digging, so you do not sever major roots.
• Note the prevailing wind. Position the pond so the wind blows leaves past it rather than into it, if you have any choice at all.
• Keep it near a tap-free water source. A water butt within hose reach makes topping up in summer far easier.

Digging, lining and shaping

Aim for at least 1.5 by 2 metres, though anything larger is better. Dig the centre to 60–75cm so the pond does not freeze solid in a hard winter, and leave a shelf around the edge at 20–25cm for marginal plants. Line with butyl or EPDM rubber over a generous layer of sand and old carpet or purpose-made underlay, especially where roots might push.

At one end, build a gently sloping pebble beach. This is a lifeline for hedgehogs, birds and amphibians that would otherwise drown trying to climb out. If young children use the garden, keep the beach shallow and the sides at the beach end gradual rather than sheer.

Fill from a water butt if you can. Tap water carries nutrients and phosphates that feed algae, and in hard-water areas it can leave the pond looking milky for weeks. If tap water is unavoidable, let the pond settle for a fortnight before planting.

Plants that cope with low light

Choose native species where possible, and plant them in baskets of loam-based compost rather than multi-purpose, which floats and leaks nutrients.

• Marginals: water forget-me-not, opposite-leaved golden saxifrage, marsh pennywort, soft rush, wood sedge and greater tussock sedge all tolerate shade happily.
• Oxygenators: hornwort and water starwort are the reliable choices for darker water.
• Edges: royal fern, lady fern and marsh marigold will sit in the damp soil around the rim, softening the liner.
• Never plant: Australian swamp stonecrop, water fern, floating pennywort or parrot's feather. These are invasive, illegal to plant in the wild, and can smother a small pond within a season.

Winning the battle with fallen leaves

This is the one job that decides whether a shady pond thrives or turns into a stagnant soup. Rotting leaves release nutrients, feed blanketweed, and consume oxygen as they break down through winter. A centimetre of sludge on the bottom is manageable; five centimetres is a problem.

• Stretch a fine net over the pond from late September to December, pegged on canes, and empty it weekly.
• Use a long-handled pond net to scoop floating leaves, and leave the debris on the edge for a day so any creatures can crawl back.
• Siphon or net out accumulated sludge in late winter, before frogspawn appears in February.
• Prune the lowest overhanging branches to lift the canopy and reduce the load.

What you can expect to move in

Frogs usually find a new pond within a season or two, sometimes within weeks. Smooth and palmate newts will follow if there is cover nearby, laying their eggs in folded leaves of water forget-me-not and starwort. Damselflies, water boatmen, pond skaters and diving beetles arrive on their own. Resist the temptation to add fish: a single goldfish will clear a spring's worth of tadpoles.

Be patient with the water. A young pond often turns pea-green in its first spring as the balance establishes, and shade will help it clear faster than a sunny one. Do not empty it in a panic. Still, unfiltered water is exactly what insects want, so skip the fountain and let it settle. By the second summer you should have a dark, quiet pool full of life, humming quietly under the trees.