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Starting to build a pond in your garden
Understanding how to build and plant your pond from the beginning will make it easier to create a successful finished focal point in your garden.
Building a garden pond
1. Siting the pond.
First think about why you want to build a pond. Is it for fish, wildlife, plants or as a patio focal point?
This decision will affect the style of the pond and its position within the garden - a wildlife pond will be a more informal shape and further down the garden and a fish pond or patio focal point likely to be a more formal shape, possibly raised up not dug down, and nearer the house. A patio container pond needs the same thought process and more detail is available on the container ponds page.
Considerations:
1. a raised pond may be safer for children and give an edge for an elderly person to sit on to work in the pond.
2. electricity to the pond - for pumps, filters, waterfalls or fountains. The supply will need to be laid on and planned for.
3. the position of underground services - sewers, pipes, cables.
4. the pond should be in a part of the garden not overhung by trees or in the shade from buildings all day.
Choose a spot with about 6 hours sunshine a day if you want waterlilies and Iris to flower but a pond in part shade can have advantages as the water will remain cooler and the pond will be less likely to have algae bloom and can be planted with foliage interest plants.
Check whether your site is level. If possible surround it on one or more sides by planting from a moist habitat/bog garden or flower bed to give a visual backdrop to the water. A rockery or sloping cobble beach may help on a sloping site or 2 smaller ponds linked by a stream.
2. Shape - either informal or formal shapes should be marked out on the ground so you can view the positioning and check for access around it. View from inside and outside the house and consider the affect of any slope on the ground and any curves to the pond edge. Build a sloping shelf cobbled exit on at least one side of the pond if you want wildlife creatures.
3. Size - make the pond with as large a surface area as your space allows. By the time you have finished and included the edging the pond itself always looks smaller than you expect. It is also easier to maintain water temperature and balance in a larger rather than a smaller pond.
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4. Dig the informal and wildlife ponds to a depth of 60-75cm(2ft-2ft 6") with a number of plant shelves at different depths - approx 15 & 30cm(6" & 12") below finished water height - as wide as possible to accomodate the different aquatic marginal plant species. Cut across the curves to give wide space - try not to build a rim of shelves around a larger surface area of deeper water as this will be unbalanced when you come to plant.
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Allow for an edging shelf to contain rocks/cobbles or other edging materials outside the area of planting shelves. The depth of this should be in proportion to your pond size - 5 - 15cm (2" - 6") dependant on the size of the edging materials you are planning to use. The rocks or cobbles will sit on a shelf within the linered area below the finished water level and should protrude above the water giving a method of escape for the wildlife. The edging of the pond is also critical visually to link the pond to the rest of the garden. |
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Showing edging shelf and rocks sat on a shelf below finished water depth |
Rocks protruding above water level - holding liner upright. No liner visible. |
Finished pond edge blends the water into the rest of the garden |
Or construct a formal raised pond from bricks and blocks either wholly or partially above ground. Build 2 lines of
blockwork built on foundations - the inner line could be block as it will not be seen and the outer line should be a
facing brick chosen to match your property or patio area. As long as you are not planning a koi pond you only need
to build to a depth of 60 - 75cm(2ft - 2ft 6") and create shelf areas within the pond at depths of 15cm and 30cm
(6"and 12") below finished water height for plants but being a more formal shape shelves can go either in the corners
or along the edges. Make them cover one quarter of the surface area as formal ponds tend to have more waterlilies
and less marginal plants and they can have fish. The inside line of block work needs to finish one face brick depth
shorter than the outer line of bricks. To accomodate plants in a koi pond a shelf area can be created at one depth
with brickwork on the deep water edge of the shelf that allows small fish and water flow through but keeps the larger
fish away from the aquatic water plants.
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Showing internal blockwall & external decorative wall - finished one brick higher |
Finished brickwork with liner trapped over top of block wall by extra line of decorative brick |
Two walls of brick with liner in between capped off with coping stone. |
In both cases the finished pond surface must be level - not by eye but using a spirit level otherwise liner will show
at one side or another and spoil the look.
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5. Underlining - After digging/building the pond profile and removing as many sharp stones as possible the hole should be lined with an underlining called geotextile. This will uphold the guarantee for the liner you use. This is purchased at a width of 2 metres and you order as many linear metres as you need. This does not need to be in one piece so you can patch some corner areas with underliner from the overlap cut away from another corner - the geotextile only needs to be one layer thick. |
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6. To retain the water use a liner. There are many choices of liner materials but 2 good alternatives to consider are butyl - available in different thicknesses, can be heavy to work with but stretches nicely around curves, available with a 30 year guarantee. Or woven polyethylene which also carries a 30 year guarantee but is a cheaper initial purchase, is lighter to work with but has no stretch so requires careful placing and folding into curves and corners. |
To calculate the size of liner needed - measure the overall length, width and depth of the hole. Double the depth to allow for the sides of the pond and add 60cms(2ft). Add this figure to both the length and width of the hole and that will give you the size of liner required.
7. Electricity - needs to be fitted correctly by a qualified electrician and a certificate received. If they connect an outdoor power socket then pumps for filters, fountains and waterfalls can be used. Solar powered pumps and fountains are becoming more popular and avoid the need for electrical installation.
8. Fit the liner to the hole allowing enough material on all sides and start to fill with water. This will weigh down the liner and you can start to fold or stretch the material into position. Make a small number of large folds in the corners rather than a large number of small folds along a curve. Make sure that the 'behind' side of any fold is always as high as the finished water height or one low fold will forever dictate the maximum height of water your pond will hold. In the informal pond shape the liner will extend over the edging shelf and finish placed vertically up to the top height of that shelf held in position by the placing of rocks or cobbles piled up against it. That shelf area will fill with water to cover about half of the depth of the edging materials.
In the formal pond the liner will be placed inside the hole and horizontally over the shorter inside block work and continue vertically to the top of the outer layer of brick. Be very careful with the corner folds checking that all edges of liner are up to the top of the brickwork. The inside wall can then be made up to the same height as the outside by mortaring an outside decorative brick onto the liner. A coping stone would be added to trap the liner on the top of the 2 layers of brick. The brick and mortar that will be in the water will need sealing with a waterproof sealant to prevent leaching.
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9. Do not trim the liner back until the pond is full of water and the edging is satisfactorily in place wedged between two upright surfaces and you have checked that the water level does not go down. |
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Preform - The alternative to working with a liner is to purchase a preformed fibreglass pond but check for shelf variety and the proportion of deep water to shelf area before you purchase and always measure your space before going to the Garden Centre so you know exactly what width and length will fit your chosen space. It is easy to be misled looking at an empty pond out of situ. |
Fitting the preform into the ground can be more tricky than you thought - mark out the profile of the pond and its shelves
on the ground and dig as near as possible to the correct shape so that the preform sits snugly in the hole. Protect the
pond with a layer of sand and bed the pond in so that it is level. Start to fill with water and place a spirit level over the
top edge. As the water starts to weigh down the pond correct the level if neccessary while backfilling with sand.
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Plant grouping - The wider shelves in the informal pond allows plant grouping to look natural. The aquatic pond plants should be placed on the shelves in their baskets in groups so that an upright plant can be softened by a rafting plant growing at its feet. If you have built a large pond that needs to look mature quickly then plant 3 of each variety into a contour basket. It is more successful if you keep aquatic pond plants in baskets rather than planting them all directly into mud on the shelves as the vigorous plants will take over the entire shelf area and the less vigorous plants will be swamped. |
Plant a formal pond shelf in large clumps of a single species in a formal layout - large square baskets (10litres) are
available that take 4x1 litre aquatic baskets and these in the corners or at regular intervals. Check the height of your intended basket before building the shelves in the pond.
Planting your pond
Use a combination of marginal aquatic plants, oxygenating plants, waterlilies and floating plants to create a healthy pond environment.
Planting the marginal shelves - Pond plants
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1. Our marginal aquatic plants can be placed immediately into your pond or patio container pond as they are already rooted in aquatic compost in open mesh baskets. You do not need to purchase any baskets or compost and do not have the worry that bareroot pieces will 'float up' when you lower the basket and plants into their position in the pond.
Images show pond plants in 11cm baskets. |
2. Before you build your pond you should check the depths of water preferred by different marginal pond plants you like and ensure you create the right depth shelving into your construction. Planting depth measurements given for each plant are from the top of the basket to the water surface level. You need to take into account the depth of the basket to calculate how deep the plant will be in the water when placed on a particular depth shelf. Basket heights: (9cm = 3", 1 litre=11cm/4" and 2 litre=15cm/ 6" tall). Water depth is vital to marginal pond plants - too deep and one variety will not thrive, too shallow and some varieties will not receive the frost/ice protection over their crowns that they would receive from deeper water.
3. Potted aquatic pond plants will quickly add foliage, colour and habitat for wildlife to the marginal pond area. Marginal pond plants can be decorative - by creating the mood of the pond - either creating a formal setting or a more informal, natural look where the plants are grouped together in mixtures of shapes and textures as in nature. The marginal aquatic plants around the pond look better in groups than in single baskets placed in lines. These aquatic pond plants help to develop the setting that allows the clear reflective water to show inside this frame. As a guidance we recommend a minimum of: 3 x 1 litre marginal aquatic baskets per metre length on a shelf, with more if the shelf is wide or if a full look is required quickly.
Shelf 0: Plants that sit with their crowns at water level: These plants will sit between cobbles or rocks and will be happy with their roots in water but with little or no water over their crowns. These plants could also grow in wet mud in a wet bog garden or on a stream edge with their crowns exposed above water level. Some of these plants could also grow on a 15 - 20cm(6-8") shelf.
Shelf 1: Plants for a shallow 15 - 20cm(6-8") shelf: These marginal shelf plants can be divided into 2 types - those that spread horizontally across the water - rafting plants, and those that spread vertically up and out of the water. Your pond should contain a mix of both to create the habitats different wildlife will enjoy. These plants are listed in the pond plant pages as accepting up to 10cm(4") of water over the top of the basket. If you have dug the shelf too deep - try replanting the plant into a taller basket so that the top of the basket is at the correct depth.
Shelf 2: Plants for a deeper 25-40cm(10-16") shelf: These plants will all enjoy a deeper shelf that will place the crown of the plant in water throughout the winter without risk of ice penetrating the pond to that depth.
4. Pond plants appreciate sunshine and need nutrients to thrive and after a season need feeding with a pond plant fertilizer.
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5. If you have taken over a pond with no shelves in its construction but want to plant marginal aquatic plants in it you will either need to create a shelf system with bricks or plant up our floating planting islands that float the crown of the plants on the water surface. These will use plants from shelf 0 category. |
Shelf 3: Plants for deeper water 45cm(18") plus: When planting a pond you also need oxygenating plants and floating plants or water lilies for the water surface area as well as the marginal pond plants to create a well balanced pond that will not look green or cloudy.
1. Oxygenating pond plants are vital to the freshness and clarity of the water. Submerged oxygenators use dissolved nitrates/mineral salts from the water thus in time helping to control algae growth through competition for mineral salts. Some varieties will also give shade to the water surface so blocking sunlight from the algae cells beneath. They need to be maintained on a regular basis so that they do not fill more than 30% of the volume of the pond or container pond.
We send some oxygenating pond plants bareroot - Ceratophyllum demersum - Hornwort. These can be dropped into the pond and will find their own depth. No weighting required.
Those submerged oxygenators that require weighting down will be supplied bunched with a weight - Myriophyllum spicatum and Potamogeton crispus. Dependant on their availability/time of season some oxygenating plants will come either bunched or ready potted in aquatic compost and so can be placed down on a shelf in the pond - Callitriche palustris and Ranunculus aquatilis. Allow two bunches or portions per square metre of surface area.
2. Waterlilies are rooted in aquatic compost when you purchase and are able to be placed immediately into your pond or the miniature waterlilies can be placed into a patio container pond.
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If the waterlily already has leaf growth that has reached the surface of our pond in the Nursery you should place it at a similar depth in your pond by standing the basket on another basket filled with gravel or equivalent. Submerging the top surface of the waterlily leaf below water level by more than a couple of inches at once will result in the leaf rotting away. The waterlily can then be gradually lowered but do not rush to take the plant all the way to its specified depth in the first year. The waterlily will see more sunshine if it is not too deep and that will enable the rhizome of the plant to grow stronger. -
There are miniature waterlilies able to have 15 - 25cm(6-10") of water over the top of the basket, dwarfs able to take 15 - 30cm(6-12") of water over the top of the basket, medium waterlilies that will accept 25 - 60cm(10-24") of water over the top of the basket and large waterlilies that could take as much as 90cm(36") of water over the top of the aquatic basket dependant on the maturity of the plant. -
Waterlilies should be positioned in sunshine but away from constantly splashing water such as a fountain or waterfall. -
They will go dormant in the winter months and show no leaf on the pond surface. They will send up new leaves in Spring when the water temperature is consistently warm. When the first leaves reach the surface of the water you need to fertilize the waterlily by pushing aquatabs into the soil surrounding the rhizome. This should be repeated throughout the summer to encourage repeat flowering. -
Waterlilies provide much needed shade to the deeper water areas keeping the pond temperature and algae growth low whilst providing colourful waterlily flowers on the pond surface. Each waterlily bloom will last for a few days and should be removed if possible before it rots down to the bottom of the pond. The aim should be to cover 70% of the water surface area with plant leaf growth in the height of summer. If your pond is newly planted this will be hard to achieve with waterlilies alone so boost the plant cover by using annual surface cover plants in the short term.
3. Annual surface cover plants or floating pond plants give shade and fast growth in their season and are supplied bareroot to drop onto the ponds surface. These are not frost hardy(Water Hyacinth, Water Lettuce or Salvinia natans) so give one season of dramatic surface cover and then need to be removed prior to winter. These floating plants also use up large amounts of nutrient as they grow. These are not available before the risk of frost is gone - usually mid May. Allow one plant or portion per square metre of free surface area.
4. Other floating plants - generally our Native varieties avoid the winter cold by dropping down below the surface of the water to overwinter as dormant buds in deeper, less cold water. These floating plants will then reappear in Spring as the water temperature warms up (Stratiotes aloides - Water Soldiers and Hydrocharis morsus-ranae - Frogbit). Other surface cover plants that grow horizontally on the water surface are Menyanthes trifoliata and Calla palustris and they are able to survive the frost and ice on the pond in winter.
Some floating plants are invasive and not recommended as if added to your pond are very hard to get rid of.
Floating pond plants to avoid are duckweed and fairy moss as they grow quickly and can completely block out light to the depths of the pond. We do not sell these.
DEFRA Be plant wise Azolla filiculoides Crassula helmsii Hydrocotyle ranunculoides Ludwigia grandiflora Myrio aquaticum
6. If you are unsure what to order then let us help. Order a planting scheme - we will send you a collection of plants so that you will receive a balanced combination of plants for a choice of depths, choice of growth habits and seasonal interest. See Planting Schemes for a selection of sizes of pond to choose from.
Building a bog garden
1. You can create an area that can be kept moist or wet by digging out 2’ of soil and lining the hole with cheap lining material like builders damp proof membrane. Add 3” depth of gravel for drainage and then puncture the membrane with a fork once every metre This will allow some drainage but keep some moisture in the soil.
2. Refill the lined hole with good soil and humus rich compost and cut the liner off at the top so it blends into the rest of the garden. This area can then be kept as wet as you like by watering from a porous or leaky hosepipe that will constantly drip when attached to a tap or water butt. This area will provide protection for wildlife species and you will find that by encouraging frogs to the area they will protect Hosta’s and other plants eaten by slugs.
3. Plants for the bog area can be chosen for a shaded site or a sunny one. Plants can also be selected to cope with more water in the soil (waterlogged in winter) or for soil that remains moist (not wet). The defenition of wet - if you dig a hole to a spades depth and it fills with water then the plant roots will be sat in water and the soil is wet.
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