Dig for glory with a large pond

Activity time:
1+ days
Difficulty level:
Hard
Suitable for:
Large garden, Neighbourhood
To help:
Frogs, toads & newts, Dragonflies & damselflies, Bats, Birds, Pond creatures

There’s something enchanting about sitting next to a garden pond, and it’s amazing how quickly wildlife will find it and create a thriving ecosystem.

In summer, it should be only a short matter of weeks before pond skaters and water beetles arrive under cover of darkness. You might get dragonflies and damselflies in your first season. And frogs and newts are likely within a year.

 

Don't be put off by flushes of algae, which are either stringy or turn the water green or brown  that's normal in a new pond.

 

You can build a pond at any time of year. But in autumn, the ground isn't too wet or dry, so it's ideal for digging.

 

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What you will need

  • Large, quality pond liner
  • Plenty of pond underlay
  • Builders' sand
  • Spade or even mini-digger
  • Wheelbarrow 
  • Spirit level
  • Pond plants – marginals and submerged
  • Aquatic baskets
  • Optional: washed gravel

Pond wildlife guide

Illustrated guide to 190 species of animals and plants in ponds

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Step-by-step guide

  1. Choose your location. Have you got room in your garden for a large pond?

    If you do, it’s one of the most rewarding things you can do for wildlife. 

    Choose a spot with plenty of sunshine and that doesn't present any flood risk. 

    Ponds often look best in the places they would form naturally – the lowest point in the garden – but it isn't essential.
  2. Design the shape of your pond. The golden rules for large ponds are:
    • shallow shelving margins
    • deeper areas (600 mm in the middle is fine)
    • plenty of submerged aquatic pondweed
    • plenty of emergent vegetation.
    You can get creative with your shape, using wiggly margins or a perfectly geometric shape.
  3. Choose your pond liner. Although it’s possible to line a pond with concrete, we recommend either:
    • A pre-moulded liner. Usually fibreglass, they are expensive but durable.
    • A flexible liner. Materials include plastic, butyl rubber and EPDM (ethylene propylene diene monomer  M-class) rubber. They’re the easiest way to create a pond to the dimensions you want, but are easily punctured so lay and look after with care. Remember, flexible liners don't do right angles!
    You’ll be really disappointed if your pond leaks, so spend wisely, not cheaply.
  4. Dig your hole. 

    Mark out where your pond is going to go  lengths of hosepipe laid on the ground or lines of builders' sand work well. For a ready-made liner, create a template in cardboard of its outline.

    Stand back and look at it from every angle, including from inside your home – does it look good?

    For really big ponds, you may want to hire someone with a mini-digger to take some of the strain. Create horizontal shelves where you will be able to put aquatic plants in pots. It’s really important to carefully check levels from each side of the hole to the other with a spirit level.

  5. Line your hole. 

    With a ready-made liner, test it in the hole until it has a bit of wriggle room, and then pack the base and sides with a protective layer of sand. 

    If using a flexible liner, dig a slightly larger hole than you need. Then make sure you remove all rocks, roots and sharp objects from the hole.

  6. Pack the base and sides. Add a 50 mm layer of sand. Then lay over man-made pond underlay – it’s like a fleece that rocks can't penetrate.

    Now you can unfold your liner across the hole, pushing it loosely into the contours. Take great care not to snag the liner  maybe take your shoes and socks off! 

    If you want to, put some washed gravel into the base  it provides cover, and it protects the liner. But if you want to use soil, only ever use the special aquatic compost, devoid of almost all nutrients – garden soil will give you algae problems for ever.

  7. Fill with water. It’s best to use rainwater, but for a large pond you will probably have to use a hose and tap. You will probably be amazed how long it takes to fill. Leave the pond for a week or so to settle and for the chlorine to evaporate. 
  8. Choose your aquatic plants. You want a range of plants which look attractive and perform different functions to keep your pond healthy.

    Submerged pondweeds in the deepest areas of the pond like rigid hornwort, whorled water-milfoil and starwort will oxygenate the water.

    Floating aquatics like pondweeds (look for those called Potamogeton), fringed water-lily Nymphoides peltata (which is smaller and less likely to overrun the pond than most other waterlilies) and water soldier provide a useful surface cover and shade for the wildlife under the water. They can be placed in deeper water too.

    Emergent and marginal plants like marsh marigold, water plantain and flowering rush are planted around the edge to provide cover for resting and nesting wildlife.

  9. Planting up. Your aquatic plant pots (they look like they are made from mesh) will come ready to be put straight in your pond. If you need to pot your plant into a bigger pot in a couple of years' time, use special aquatic compost which is low in nutrients. 

    Once you’ve planted it, spread a layer of small gravel around the top of the pot to stop the compost being washed into the water.

    You shouldn't need to bring in any wildlife at all. Don't move amphibians – you risk spreading the viruses they suffer from. 

  10. Aftercare. For the first few months, don’t worry if blanket weed keeps trying to overrun your pond (it’s like strings of green gloop). Get children to remove it by winding it around a stick – it’s fun! 

    Don't be put off by flushes of algae, which are either stringy or turn the water green or brown - that's normal in a new pond. As your pond matures, all the pond creatures you’ve attracted will help keep the water clear. 

    You may need to top the pond up in hot weather – try to use rainwater from a water butt.
Frog

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