I’ve previously written about the pond we acquired when we moved house. It started life as a very deep, formal pond for Koi carp, but we’ve been transforming it into a home for wildlife. The liner had to be replaced, as I think it was leaking (and I wanted to re-shape the pond and reduce the depth too).

To protect the liner, I put the old underlay into the hole, and then a layer of new underlay over it. Next was the liner itself, followed by another layer of underlay over that. I know this sounds strange – it’s called underlay, not overlay after all; the clue’s in the name – but the idea is to protect the liner from being damaged by anything sharp that might be put on top, such as plant pots, bricks and slabs for raising up water lilies, and any stones or sharp objects that might be in the soil you put in for marginal plants.

I wanted to get it right, so I followed instructions in a book called ‘The Water Gardener’ by Anthony Archer-Wills, apparently a very respected figure in the industry. The book isn’t always entirely clear on the details, and I’m not convinced about some of the construction methods – more on that later. This is the pond the next day, when snow and cold weather stopped play…

You can see I built a shelf for planting all the way around the perimeter, and bricks along the edge of the shelf to stop the earth collapsing. In the deep section there are two slabs, supported on bricks, for a water lily and a water hyacinth.

By the middle of March, the frogs had moved back in, and had started laying frog spawn…

I think I got the pond filled just in time. Last year I think most of the tadpoles were eaten by the fish, but they’ve been relocated elsewhere, so the tadpoles should have less predators this year. Panning out, this is what the pond looked like at that time. You can see we’ve planted the far side with some dogwoods: Cornus sanguinea ‘Midwinter Fire (times 1) and Cornus alba ‘Sibirica’ (times 2). It needs more, but I’ll take some cuttings this year, and try to be patient

The water got cloudier and cloudier, and a scum of green algae formed on the surface – it didn’t look very appetising. Something had to be done. Rather than spending a fortune on bags and bags of aquatic compost, I had just used garden soil on the pond shelf – which is, I believe, as the book directed. I wondered though – could all the nutrients in the soil mean that the pond would inevitably remain scummy?

I remembered reading that putting bunches of lavender in a pond will clear the water. Obviously, at that time, there was no lavender to be had. So instead, I tried rosemary. I couldn’t imagine it would work. But, amazingly, it did – after only a week, the water had cleared, and the algae had disappeared. Surprisingly, the water has got clearer and clearer. So much so, you can see right down to the bottom. And the tadpoles have now hatched….

The water may be clear, but there is a bit of a problem with the level – it’s going steadily down. I’ve been emptying a water butt into it now and then, but that’s not enough. I think the problem is that the water is wicking out and over the sides via the layer of underlay over the top. The book did say you might need to have a system to top up the water, but it’s just losing too much. Mains water isn’t great for topping up a wildlife pond (and the supply is too far away anyway). There’s only so much rainwater you can collect. I’ve already got three water butts, but the water in those will be needed for watering plants when the prolonged dry spells arrive. Here is the edge, with the underlay lapping over and tucked into the soil around the pond…

To stop the water loss, I’ve cut away the under (over?) lay so that the liner, which of course isn’t absorbent, is exposed. The next problem is how to hide the liner. I’ll have to top up the soil on the ledges. Hopefully the plants should hide most of it once they’ve grown up. I may just need to put some stones around the edge too…

Don’t let anyone say I don’t fill this blog with pretty pictures! To the left (front) side of the pond the liner dips down and extends under the width of the bed to create a bog garden for plants that like damp soil (Ligularia, Rodgersia, Hostas, Iris sibirica, etc.). I’ve left the under (over!) lay on that side because I want the water to over-flow into that bed when there’s been a lot of rain. I’ve also run a pipe from the down-pipe on the side of the workshop where there isn’t room for a water butt. So the rain that lands on that face of the roof feeds straight into the pond. Hopefully that will fix the problem with the water levels. This is how the pond was looking a few days ago…

The water hyacinth is flowering nicely. You can see the water level still needs to come up somewhat. Hopefully that will happen in time. We’ve planted up the bed on the left of the pond with damp-loving perennials (from Claire Austin, as well as Ligularia seedlings and Iris divisions that we brought with us from our previous garden). They’re not showing much as yet – hopefully they will put on some growth over the summer. We’ve got tadpoles, water beetles and water boatmen. It might take a few years, but I can’t wait until there are dragon flies and damsel flies skimming back and forth over the surface all summer long…

Text & images © Graham Wright 2021