How to build a Garden Pond

 

Cotton grass Eriophorum angustifolium Lily pads Zantedeschia aethiopica

 

How to build a Garden Pond.

To construct a good garden pond forward planning is key; right down to the detail of thinking about what types of plants you want to grow, as this will impact on how you construct the pond and it's depth.

There are several stages to building a pond:

Decide on position

Size and depth of the pond

Shape the hole

Form shelves and planting pockets

Level the hole and shelves

Soft lining (optional)

Cement to secure (optional)

Fit the liner Preformed or Butyl

Fill and plant

How to Build a Garden pond and where to put it.

The position of the pond in the garden is important for a number of reasons. Putting the pond in the right place adds to the success of the pond by encouraging plants to flower and to discourage green water caused by algae as much as possible. A pond is best placed where it will get a good amount of sunshine around 8 hours per day. This is particularly so if you want to grow water lilies, which are truly beautiful , but do require sun to flower well. It is a good idea to site a pond away from deciduous trees because the leaves  will fall into the pond and  by doing so add to the organic matter, which decays, increasing formation of algae which turns the pond green.  If you are intending to have a water feature, such as a waterfall, the pump will require a power source which will need to be close to the pond.  The combination  of water and electricity requires that the  electrical work  should be undertaken by a qualified electrician.  Bear in mind also that a waterfall will have to be raised, so a small mound, or higher point, needs to be added into the design. Finally, often in a hot summer pond water evaporates as a result it may be necessary to top it up, so the pond site needs to be within reach of a hose.  Also check and be sure not to site the pond in an area where there are any drains, cables or pipes that you may dig into when excavating the hole.

Pond with Jetty Apart from these points, it comes down to personal choice where to put a pond;  near the patio/seating area so that you can sit and enjoy the tranquility and the wildlife, or hidden in a secluded part of the garden to create a different area of interest.

Before you dig the hole, bear in mind maintenance. Garden ponds do require some attention and periodically it maybe necessary to get into the pond to reach the plants in the centre if they cannot be reached from the pond edges. This is best done wearing waders and if the pond is too deep the water will be close to the top of the waders. There is risk when you bend down to pick up the plant from the bottom of the pond the water will seap into the waders. Easy access to the  middle of the pond can be provided by building a jetty which looks good as well see image left.

 

 

marking out pondBuilding a Garden Pond: Size and depth

 

Before you can dig out the pond, you need to decide how deep you want to pond to be and this will depend what you are going to do with the pond. A minimum depth would be around 60 cms  which would be sufficient for non ornamental fish and most pond plants. There are some types of lilies, Nymphaea alba (Common white water lily) which has planting depth of 30-90 cms, but 60cms will accommodate most plants. In addition many attractive plants are marginals which need shallow areas and so before constructing the pond it’s helpful to consider what plants you would like to grow. Bear in mind that different plants require particular depths of water to grow depending on the variety and type. This is why forward planning is important down to detail such as what plants are to be grown. Otherwise you may dig out the pond and find the depths are wrong for what you would like to grow.

Getting it level is crucial

 Check the conditions the plant requires, how deep it needs to be and it’s spread. The size of the pond will depend on space available and personal preference.  Once decided it is a good tip to mark out the proposed pond with garden hose, or sand in a plastic  bottle, string, or paint spray so you have a visual plan showing the position of the pond relevant to the rest of the garden, see image. 

If your pond is for wildlife, there will need to be shallow areas where wildlife can get into the water and a shallow sloping beach for access is a good idea.

 

 

 

How to dig out and shape a Garden Pond

 

Channel to deal with underground water

Once you have marked out the pond the next step is to dig it out. Depending on the size you can do it by hand or hire help with a digger. Even if you get a digger to shift the bulk of the soil, the finishing and shaping is best done by hand. You must ensure the pond and all the shelves are level, this is essential. Use wooden pegs around the pond and check using a spirit level to ensure it is level. The image shows pegs in place with string to check the level.  

 

 When building a pond it is important to ensure the pond is absolutely level which is crucial, all planting pockets are flat, and that any and all stones are removed as they are a threat to the integrity of the liner.   

 The nature of the ground where the pond is being dug can cause problems particularly if it is stony, or wet. At this stage, is worth spending time removing all 

Pond Jetty

pebbles, stones and sharp edges. Pond liner is expensive and if punctured obviously it will leak, which is exactly what you don’t want as that is a major headache to solve. Weight of water causes pressure to push down on any stones so careful preparation at this stage is tedious but worthwhile in the long run. The other problem with flinty ground is that it is very difficult to shape the pond and shelves, rocky ground does not hold its shape and if this is a problem it can be overcome by cementing the pond.

Wet ground is a challenge. If your garden is close to the water table or in wet ground, contrary to instincts, this is a problem when constructing a pond. You may guess that the land is close to the water table because of pooling water after rain, areas of wet or boggy ground in the garden, or the presence of water loving plants. Wet ground will causing pooling in the bottom of the pond during construction and this in itself is a problem. Once the hole is dug the fact it fills repeatedly with water can once the liner is in place, can cause a build up pressure under a pre formed or Butyl liner pushing the liner or parts of it upwards. The problem can be approached to change to construction by raising the pond above the water level. Use landscaping to raise the edges of the pond so that the liner does not have to be laid so deep. Alternatively, build a permanent pipe or channel to funnel the water out as in the image. When digging started  on the pond in the image,  it was unknown that the position was over a spring well and the problem could only be resolved with permanent drainage. By that time a very large hole had been dug, and so not everything can be planned for.  

For all ponds once the hole is dug out it needs to be lined with sand. This should be a firm layer of several centimeters, more if you are on stoney ground. This is needed to protect the liner and the sand acts as a cushion. Remove all stones and sharp objects from the hole before adding a protective underlay of soft sand. A preformed liner will need to be placed on the ground where the pond is to be constructed, which is best drawn around to the shape of the liner. Use a cane to measure the depth of the preformed liner and then dig out to that level.  If your pond is quite deep and large, consider how to make the maintenance easier. Pond plants require attention such as cutting back, especially lilies, which if growing in the center of the pond will need to be accessed. This can be done either by getting into the pond or by constructing a Jetty. If you intend getting into the pond, make it easy and at the construction stage plan a set point of access into the pond with some step down free from planting.

 

Making plant shelves and planting pockets in a garden pond

  

Cementing a pondThe image show a pond which has been cemented because the ground was flinty and the ground would not hold a shape. Building a pond does depend on the ground and these are all ideas from which you can pick and choose what suits your garden. In the image you can see clearly the shelves for baskets at different depths.

 

Important to the construction of the pond is planting depths of the various pond plants. When planting into the garden border, the plant label indicates the planting depth required and also by virtue of the plant size. Under water in a pond you are creating the planting environment, different depths for different pond plants  according to their growing requirements.

If you intend to grow in baskets, you will need to incorporate shelves in the side of the pond structure. It sounds obvious but measure the size of the baskets and 

pond partly constructed with planting pockets and shallow beach

allow for extra growth to make the size of the shelf, and ensure it is level. The depth of the shelf should be between 20-30cms. The vertical sides of the shelves should slope gently around 20 degrees to prevent the soil caving in.

If you are growing plants around the edge of the pond this can be done either on a long shelf to accommodate baskets, or without baskets, by creating an internal wall forming a planting pocket which will contain the planting within that area.  The image left  shows in the (currently) unlined area two larges shallow planting pockets . This can look more natural, see image, but requires more construction work.  In a planting pocket growth is not as controllable as in a basket. Some pond plants are very vigorous and can be invasive and should be grown in baskets to contain them.

Planting pockets enable you to achieve a naturalistic planting style whilst still keeping control of the plants, many of which are vigorous growers.  To make a large planting pocket form a large shallow shelf about 10 cms below the water and along the edge lying inwards of the pool, build a shallow wall to act as a container for the planting pocket. The wall will contain cement which will need to be sealed and there are various aqua sealants on the market. It brushes on with a paintbrush as a clear varnish and ensures the wall is sealed.

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