How do I make a small wildlife pond?

A pond is the single most effective thing most gardens can add for wildlife, and a small one works. What determines whether it becomes a habitat is not size but shape: the gently sloping shallow edge is where nearly all the life is, and it is the feature most ornamental ponds leave out.

Safety

What you'll need

• Spade and a straight edge with a spirit level
• Underlay — old carpet, sand or purpose-made fleece
• Butyl or EPDM pond liner
• Stones, turf or slabs for the edges
• Rainwater from a butt
• Native marginal and oxygenating plants
• Rigid metal grille if children have access (optional)

Step by step

1. Choose the position carefully.Open and sunny for at least half the day, away from overhanging deciduous trees whose leaves fill it every autumn, and away from anywhere a child could fall in from a step or wall. Somewhere you will see it from the house makes it far more rewarding.
2. Decide the safety approach before you dig.If young children have access now or are likely to, plan for a rigid metal grille at or just below the surface, or a fence with a self-closing self-latching gate. Retrofitting is much harder than designing it in.
3. Check for buried services.Electricity, gas, water and drainage runs cross most gardens. Check plans, use a detector if you have one, and dig the first spit carefully.
4. Get the profile right — this is the whole design.A wide gently sloping beach on at least one side, from nothing to about 100mm deep. A marginal shelf at 200 to 250mm, wide enough to stand a planting basket on. A deeper zone of 400 to 600mm in the middle.
5. Understand what each depth does.The beach is where birds drink and bathe, where amphibians get in and out, and where insects that fall in can climb out — it holds most of the life. The shelf carries the marginal planting. The deep zone stops the pond freezing solid or overheating and gives amphibians a refuge.
6. Level the rim.A straight board and a spirit level across the hole. A rim out of level shows as liner on one side and water spilling on the other, and it is very difficult to correct afterwards.
7. Remove every stone and root, then underlay.A layer of old carpet, sand or pond fleece over the whole excavation. Liners are punctured from below far more often than from above.
8. Fit the liner loosely with plenty of overlap.Butyl or EPDM lasts decades. Lay it in on a warm day when it is supple, press it into the contours, and leave a generous margin all round. Fill slowly and let the water pull it into shape.
9. Fill with rainwater.From a butt if you can. Tap water is high in nutrients and lime and reliably produces an algal bloom in the first months. If you must use tap water, let the pond stand for a few weeks before planting.
10. Hide the liner edges completely.Under stones, slabs or turf brought over the rim. Exposed liner degrades in ultraviolet, looks wrong, and gives no route in and out at the edge.
11. Plant sparingly and let it fill in.Marginals on the shelf — marsh marigold, water forget-me-not, water mint, flowering rush, purple loosestrife. Submerged oxygenators such as hornwort and water crowfoot in the deep zone. One or two floating-leaved plants for surface cover. Aim for roughly half the surface covered eventually.
12. Use native plants and check what you buy.Several invasive aquatic species are banned from sale and are ecologically serious if they escape into watercourses. Buy from a reputable supplier, choose natives, and never tip pond plants or water into a stream, ditch or drain.
13. Add nothing else.No fish, which eat the tadpoles and invertebrates the pond exists for. No fountain or waterfall, because still water suits far more species and moving water drives off the surface film many insects use. No spawn or animals brought from elsewhere, which spreads disease — everything arrives on its own.
14. Make sure there is a way out.The beach does most of it. Add a piece of rough timber or a line of stones as a ramp on the steeper sides so hedgehogs and small mammals that fall in can get out.
15. Maintain it lightly and at the right time.Pull excess blanketweed out by twisting it onto a stick, leave it on the side for a day so creatures can crawl back, then compost it. Clear silt and cut back marginals in late autumn, not in spring when everything is breeding.

Tips

• A washing-up bowl or an old sink sunk into the ground with stones as a ramp attracts insects and birds within weeks. Scale is much less important than a shallow accessible edge.
• Do not introduce frogspawn from another pond. It spreads disease, and frogs find new ponds on their own remarkably quickly.
• Blanketweed in the first year or two is normal while the nutrient balance settles. Rainwater, planting and patience deal with it; chemicals mostly do not.

Common mistakes

• Steep sides all round — Nothing can get in or out, and you lose the shallow zone where most of the life would be. It is the difference between a pond and a tank.
• Adding fish — Fish eat tadpoles, newt larvae and aquatic invertebrates. A pond with fish is an ornamental feature; a pond without them is a habitat.
• Filling with tap water — The nutrients and lime in mains water reliably produce an algal bloom. Rainwater from a butt is much better.
• Siting it under a tree — Autumn leaves fill it, rot down and turn the water anaerobic. Netting it every autumn is a chore you can design out.
• Assuming a small pond is safe around children — A child can drown in a very shallow depth of water. A rigid grille or a properly gated fence is the answer, and it needs checking regularly.

If it doesn't work

Questions people ask