James Holloway
Why a pond without fish works best
The single most important decision you will make about a wildlife pond is what you leave out of it. Fish — goldfish, koi, even the modest stickleback — will clear a pond of frogspawn, tadpoles, newt larvae and the nymphs of dragonflies and damselflies within a season. A wildlife pond is essentially a nursery, and a nursery with a predator in it does not function.
Leave the fish out and you get the full pageant: common frogs and smooth newts spawning in the shallows, dragonflies patrolling from May, and a summer chorus after dusk that makes the effort worth every wheelbarrow of clay you shift. You also get an ally against slugs and aphids — a healthy garden pond is a bug-munching engine that never needs feeding or a filter.
Choosing the right spot
Site your pond where it gets a good few hours of sun for dragonflies to bask and warm, but with some shade during the hottest part of the afternoon to keep algae in check. A south or south-west aspect is ideal. What you do not want is a position directly beneath a deciduous tree or hedge: leaf fall in autumn decays and turns the water to soup.
Keep it away from where you spray, from the runoff of a muckheap or livestock yard, and from any spot that already floods in winter. And do think about safety if you have small children — a pond of a metre or so deep, with sloping rather than vertical sides, is far easier to negotiate than a steep-sided pit. If you have toddlers, consider fencing one side and keeping a simple plank or stone ramp at the shallow end for them — and for the hedgehogs.
Digging for depth and variety
A useful working size is around 2.5 metres by 3 metres, but any pond is better than none. The shape matters more than the footprint. Aim for three distinct zones:
- Marginal shelf, 10–20 cm deep: this is where frogs will spawn and where most native marginals grow. Make it wide — at least 30 cm — and generous around one half of the pond.
- Mid-water zone, 40–50 cm deep: home to oxygenating plants and the deeper-rooting water lilies.
- Deep sump, 60–75 cm deep: critical. Frogs hibernate in the bottom mud, and a pond that freezes solid kills them. A small area of this depth is enough.
Give the sides a gentle slope on one side — a 30–45 degree angle lets frogs, hedgehogs and birds climb in and out — and, if you can manage it, a shallow "beach" at one end.
Line the hole with a good polyester fleece underlay, then a butyl liner of at least 1 mm thickness. Allow a generous 30 cm of overhang all round and tuck it into a shallow trench, weighing the edge down with turf and stones. Leave the shelf edges soft; turf and native planting will hide the liner within two seasons.
Planting with natives, not ornamentals
Fill the pond with rainwater from a water butt if you can. Tap water carries nutrients and phosphates that feed algae, so if you must use it, fill and leave the pond to stand for at least a week before planting.
Plant in baskets of aquatic soil topped with grit, or directly into a thin layer of soil in the deep zone. Good natives to start with:
- Oxygenators: hornwort, curled pondweed and water starwort.
- Marginals: marsh marigold, water forget-me-not, water mint, yellow flag iris, ragged robin.
- Floating: a small native water lily and frogbit, which shades the water and starves algae of light.
Avoid the invasives that wreck small ponds — floating pennywort, parrot's feather, water fern and New Zealand pygmyweed — and never tip surplus pond plants into a stream or ditch.
Patience, and the first two seasons
New ponds go green. It is normal, and it usually settles after the first summer as plants establish and grazing invertebrates arrive. Do not be tempted to drain and start again. Barley straw is widely used for blanketweed, though the evidence is mixed; pulling excess weed out with a fork in late summer, and leaving it on the edge overnight so that creatures can crawl back, is more reliable.
Wildlife will come without help. Frogs find ponds within a year or two, dragonflies within weeks. If you are impatient, borrow a jam jar of water and weed from a friend's healthy pond — but never move spawn or plants from the wild.
From then on, maintenance is light: cut back excess growth in late summer, keep the surrounding grass rough and unsprayed, and leave a log pile nearby for overwintering amphibians. Do nothing in winter, and very little in spring. The pond will do the rest.
