Over the past year, I have built myself a pond in my garden. I have learnt several lessons, which I wish to share. The most important is that, contrary to popular belief, the building of a pond doesn’t stop immediately after contruction. If you are willing to experiment and make changes as you go along, you can have any kind of pond that you like.
Most of the information available on building ponds encourages the gardener to decide on a ‘purpose’ for their pond before they start. There seem to be two camps:
1. The ornamental pond. Make sure that the pond is in an ideal position with regard to shading. Stock the pond with all of the pretty plants that you can find as soon as possible. Don’t ever do anything that isn’t by the book. The Wickes Guide is a good example.
2. The wildlife pond. Don’t worry too much about the details – a pond is a pond is a pond. Pond Conservation is one of the key adversaries of this type of pond building.
As someone who has done some pretty extensive study on the dynamics of garden ponds within the environment, I recognise that they can be an incredibly valuable contributor to national biodiversity when route 2 is followed. On the contrary, ponds whose owners have chosen route 1 tend to produce ponds which are capable of spreading invasive species across the landscape whilst supporting very few native species. Of course, this is a vast generalisation. But, as a general rule, I have found that it holds up to scrutiny (Bishop and Sayer, unpublished data).
The problem is that most people – myself included – want a garden pond that is going to look attractive but also attract wildlife. So, when I went about building my pond, I tried to combine the two approaches to create a ‘multi-purpose pond’. This is how I did it.
1. Choosing a location for my pond.
It is often recommended that ponds should be placed in positions where they receive plenty of sunlight. My garden is a fairly average sized suburban garden. This meant that I couldn’t put the pond fully in the sunlight because it would have ended up right in the middle of the lawn. The edge of the garden is lined with a hedge/tall bushes, so anywhere there would have been completely in the shade. So I based my decision completely on where it would look best and be most convenient. Which just happened to be underneath a tree (a place which is often seen as an ill-advised place to build a pond). So I went with it. It receives dappled sunlight through the branches of the tree, and receives a high organic input from the tree above. But hey, a pond is a pond is a pond, right?
The first few shovels…
2. Deciding on a shape for my pond.
I had a fairly small area in which to build my pond. And I knew that I didn’t want it to be perfectly circular, but a rather more traditional ‘wonky kidney bean’ shape. So, with this idea in mind, I recruited my fiancee and we dug. There was no plan, and no markings made to guide us. We dug some bits deeper than others, and generally tried to put as much variation into the pond as possible. I was very set on having shallow sloping sides to allow wildlife to get in and out, and, although we didn’t achieve this all the way around the pond, we did manage to get some in.
We ended up with three separate sections in the pond – one deep pool (about 2ft deep), one pool of medium depth (1ft) and one shallow pool of only about 15cm depth. This was contrary to all of the advice out there that ponds should be no deeper than 1ft. So, just as the location was a bit ‘ad hoc’, so was the shape.
Handy location in the corner of the garden.
3. Checking the level.
This is a vital step in the construction of any pond. Unfortunately, given the slapdash approach that I had taken to this point, I hadn’t really considered this until I had chosen my spot and dug my hole. It is incredibly important to use a spirit level to check that what will be the surface of your pond will be on a horizontal, otherwise your pond will end up looking incredibly wonky. This resulted in a small earth mound being made along one edge of my pond to level it out, but it seemed to work okay. Luckily, I had been sensible enough to choose a flat spot!
4. Lining the pond.
Another vital step. There are numerous different options available for pond linings, from cheap moulded plastic liners to incredibly expensive concrete. I paid about £40 for a flexible butyl liner, and found this incredibly easy to use. Before laying the liner, I laid a protective bottom sheet that I found in B&Q and was made specifically for this purpose. This was included in the £40 total. This needed to be weighed down with rocks until the butyl liner went ontop, but it didn’t present any major problems. It did help to prevent the underside of the butyl from getting caught on the rocks that I was too lazy to remove from the bottom of my hole though.
Protective bottom sheet.
5. Filling the pond.
Advice for filling the pond is more or less the same wherever you look – fill it with rainwater rather than from a hose. Tap water, in general, contains much higher levels of phosphates and nitrates than rain water. This is important, because these nutrients allow plants to grow. So why not use the tap and put in as many as possible? Because I do not want the pond to be overgrown with algae (which is a type of plant). Neither do I want the pond to be overrun by plants. I would like some plants there, but not so many that the entire pond is covered with them. I therefore wish to limit the nutrients available in the water. Rain water is the clear choice. I had the foresight to collect rainwater in a waterbutt in the garden before building the pond. If you do not do this, then unfortunately the only solution is to wait for mother nature to fill your pond.
The water level slowly rises…
6. Creating habitats for invertebrates and amphibians.
This was the fun bit! One of the main critiques of artificial ponds when it comes to conservation is that they tend to have very steeply sloping sides. This does not make it easy for invertebrates and amphibians to get into the pond. Both invertebrates and amphibians are vital parts of the food chain that drives the ecological functioning of a healthy pond. For example, if there were no invertebrates in the pond, there would be nothing to eat the algae and the pond water would become very green and the sediment sludgy and smelly.
I made a special effort to create a wide range of access slopes to and habitats within my pond. The idea was to provide homes for as many different species with as many different habitat requirements as possible. I created a gravel bank and bed for beetle larvae to hide in, dark spaces under rocks for frogs and newts, a bed of vegetation (see below) for smaller larvae to shelter and to provide food, and a sloping log to allow species access to the deeper parts of the pond directly from the bank. Finally, I added some turf to one side in order to give direct access to the human (myself!) who wanted to see into the pond!
Log to provide easy access to the pond.
The (almost) finished look.
7. Planting the pond.
The ‘Pond Conservation’ types will tell you that a pond should not be planted at all. Plants will naturally disperse to your pond, establish themselves there and grow if the conditions are right. This is all very well and good, but it could take a long time for plants to find their way to your pond – they rely on dispersal of the seeds by wind or through the guts of water fowl. It will take at least one growing season (i.e. one year) for anything to establish in your pond.
Conversely, the ornamentalists will list a huge variety of plants that you should plant in your pond. Exotic flowers, unusual variants of water lily, exotic grasses, not to mention the dreaded ‘oxygenating plants’. Curly water weed; Canadian pondweed; In fact, almost all of the curly Elodea species sold by garden centres are incredibly invasive. They will not only take over your entire pond, outgrowing anything else that should live there, but they will spread easily into the wild and clog up other ponds and lakes. They have been found to have negative effects on fisheries, navigation, water abstraction, water quality and biodiversity. Worst of all, they are often incorrectly labelled as ‘native’ and ‘essential for pond life’ in garden centres, when they are, in fact, neither of these things.
I am lucky. I have a good enough knowledge of the taxonomy of water plants to know what is what. I therefore made sure that I planted only native species in my pond. I was also careful not to over-plant; I left about 80% of the pond unplanted, to allow other species to naturally disperse into my pond without being over-competed. Specifically, I planted the native lily Nuphar lutens, aquatic mint Menthus aquaticus and the popular yet common native ornamental yellow Iris Iris psuedocorus. I planted them in baskets, so as to retain some sediment for them to continue to grow in until the time that sediment begins to collect naturally. The idea was that these plants would give a good visual effect without blocking the light or oxygen penetration of the rest of the pond. I am relying on the mixing effect of currents created by the wind to feed oxygen into the water.
I do not claim this to be the best way of building a pond, rather an ongoing experiment. I expect to have to alter certain aspects as time goes on, but am hoping that the pond will not require the extensive management that many ornamental ponds do. Perhaps an annual MOT and service if required. I will, of course, post my updates and findings here. The main message that I wish to convey in this post is that rules are made to be broken. As they say, any pond is a valuable habitat. It is the fact that the different types of pond are so diverse that makes them an important feature in any natural habitat. What is to stop your garden pond adding to this diversity? Go out and experiment. It is not as difficult as you think.