The Wildlife Pond

Water is a key element in a wildlife garden.  Garden ponds attract an enormous range of living creatures, such as dragon flies, newts and birds, to name but a few of the insects and animals that will visit the garden.  Some will come to drink or bathe, others will set up permanent residence there.  A pond not only provides an attractive feature in your garden, but also has far-reaching benefits for wildlife.

There are a number of points that you must be aware of if you want to provide a safe and healthy environment for wildlife.  A pond should always be sited in a sunny position, because many pond plants will not thrive in the shade, while the water may also be rather cold until the early summer.  Shade within the pool is best achieved by surface vegetation, although a pond may have up to a third of the surface in shade if the remainder is well lit.  You should avoid a site near to overhanging trees whose shade can cause the water to be colder for longer in the spring.  Falling leaves can cause a build-up of nutrients and increase the potential for toxic tannins in the water.  The root of some species may also interfere with the lining of the pond and can, in extreme cases, cause serious damage.

Never fill your pond with tapwater, which often contains many additives, most notably chlorine.  Much tapwater can have a high pH and may contain phospates or nitrates.  These can raise the pond's nutrient levels and promote algal growth.  Water runoff from nearby lawns or borders can have much the same effect.  If the water level becomes very low during the summer it is possible to use solarized mains water to top up your pond.  This involves filling large containers with tap water, partially covering the tops and leaving them to stand in the sun for a couple of days.  It removes chemicals like chlorine and, although not as good as rainwater, it will stop your pond from drying out.  The majority of pool life requires a still environment, so avoid introducing pumps, fountains or filters.

Even small-scale ponds can support an amazing diversity of life.  The shallows are the most important areas for wildlife but a depth of at least 60cm (24in) must be reached in some parts to give creatures a place to which they can escape in extreme heat, cold or drought.  The greater the surface area of a pond, the deeper it has to be (at its deepest point) to maintain an even temperature throughout the year.  The average pond will need to be about 1m (3ft) deep.

Ponds that are designed to attract wildlife should be colonized naturally within a couple of years.  This is the best method for stocking your pond in the first instance as it is providing a breeding place or hibernating area for those creatures already established in your area.  Introducing frog spawn can sometimes spread diseases such as red leg that can devastate populations of frogs and other amphibians.  Never attempt to introduce adult amphibians to your pond.  They have an amazingly strong homing instinct and can die in the process of finding their way back.

Bank-side vegetation provides cover for animals entering or leaving the pond.  Choose a selection of marginal plants, submerged plants and plants with floating leaves.  Leaving long grass around the pond will also provide important cover for wildlife.  Gently sloping sides make it easier for creatures to climb in and out of the pond.  Pond dwellers such as dragon flies and caddis flies need vegetation to climb out of the water.  Small reeds such as the lesser bulrush are ideal but any plants that grow about 40cm (16in) or more above the normal water surface will do.

A logpile nearby will provide a place for hibernating frogs and toads, as well as being a habitat for many other creatures.  Ideally the water surface should have a third or more covered with plant leaves such as water lillies, water soldier, frog-bit or even duckweed.  These help keep the water cool, provide shelter and breeding cover for wildlife and help to prevent the development of algae in the water.

Plants that are to form part of your pond habitat should always be grown in a nutrient-poor potting mix.  Slow release fertilizers effectively act as an algal 'time bomb', steadily releasing a supply of nutrients that encourage green water and blanket weed development.  Oxygen is essential for the growth and development of pond dwelling creatures and can easily be boosted by the inclusion of plants that release it directly into the water.  These are plants that are entirely aquatic and do not emerge above the water surface.  Plants such as milfoli and Canadian pondweed are often used for this purpose.

Native plants should be a first choice for a pond.  If you decide to use natives, never take them from the wild.  Always buy them from a reputable nursery or take small cuttings from a friend's pond.  Some plants are just too vigorous to be included and will rapidly outgrow their space.  Reedmace (Typha latifolia), reeds such as phragmites, floaters such as duckweed (Lemna) and Azolia fern are all potentially problematic and should only be included where space permits.  They are the equivalent of aquatic weeds and may cause maintenance problems.