A Natural Pond in your Garden?

Kathie and Peter Strickland

So you want to build a pond in your garden. These days your first consideration must be where does the water come from?

Many councils and water companies now have water restrictions which prevent pools of any sort being filled from reticulated water supplies. Unless you have your own tanks or farm dam, relying on rain water during the drier months may be a problem, especially with the high evaporation in smaller ponds.

The siting of the pond to take into account runoff after rain is important, as is the base of the pond. Natural lakes, waterholes and wetlands are subject to varying water levels during the year. The varying depths are important in providing opportunities for various plants, water insects and birds to survive. There is no reason why the same characteristics found in larger wetlands should not be reflected in garden ponds.

Large dams and wetlands have an impervious layer of pounded clay at their base; small pond bases may need a heavy plastic inlay or concrete, especially in pervious sandy soils.

A successful design will include a deep end; say at least 600 mm [Ed: check with your local council on the maximum depth allowed for an unfenced pond], an intermediate depth, and a graduated beach-like section. This will provide varying depths of water, even during the dry period, where the plants and animals can survive.

Where there is a plastic or concrete base, larger plants can be kept in sunken pots if the area or depth does not permit a reasonable thickness of soil in the bottom. It also enables larger plants to be removed or altered with little work. For the shallow end, the smaller plants may not need so much soil.

The garden pond is home to aquatic insects, while many amphibians, small mammals and birds make use of them. Birds especially use them as they fly around the country. Your pond will, of course, collect leaves, which, together with small sticks etc, will provide excellent habitat for the aquatic life in general.The vegetable material tends to wash down to the deeper area and will pack down. Native aquatic plants are therefore important, and insects will find your pond. It is against the law to bring in tadpoles but in the right environment the frogs will help.

Some pond life which might appear includes water hog, marsh treader, fisher spider, freshwater shrimp, and dragon and damsel flies. These in turn will attract bird and animal life, especially skinks in the garden situation.

Those with sloping ground might consider two ponds and a linking waterfall. Naturally this would require a small pump to recycle the water and keep it fresh. There are some very neat solar panels and pumps available. Rocks and tree stumps on their sides around the pond all help to provide habitat and interest. If there is stormwater runoff, especially from roads or shed roofs, causing a stream of silt, a lining of fist-sized rocks will help to cleanse the water and remove silt before it enters the pond.

Planting in and around ponds

A range of native aquatic and semi-aquatic land plants will provide food and shelter for animals and insects visiting the pond and add to the pleasure of pond watching. Species mentioned which attract butterflies are Goodenia sp, Lomandra longifolia, Mazus pumilo and Leptospermum sp. If your pond surrounds are covered with grass, avoid mowing as the wood ducks like short grass and a visiting flock can pollute your banks and water. Grow native grass which requires cutting once a year and can be left 10 cm high.

Fist-sized rocks filter run-off, while larger boulders provide interest and habitat Photo: Kathie and Peter Strickland

Submerged rooted aquatics help to stabilise the bottom sediments and keep water sweet. Species include Lepilaena preissii, slender water mat, with slender thread-like branches; Potamogeton ochreatus, short pondweed, with flat linear leaves; Ruppia maritima, sea tassel, with find branched stems; and Vallisneria americana var. americana, ribbonweed, which has broad strap-like leaves which, when the water depth is right, will appear to float on the surface.

Emergent rooted aquatic herbs of various heights include Alisma plantago- aquatica, water-plantain, which grows to 1.5 m. It has a panicle of white or pale pink flowers. Both flowers and fruit are eaten by animals; Ottelia ovalifolia, swamp-lily, a tufted herb with cordate leaves to 16 cm long and petioles to around 1 m. Emergent flower are up to 5 cm in diameter, white with purple bases, submerged flowers remain unopened and are self-pollinated; Potamogeton sulcatus, floating-pondweed, has submerged leaves to 20cm long and thick waxy floating leaves to 10 cm. It can become a problem if not controlled, but seeds are a source of food for water birds.

Tufted plants include Eleocharis sphacelata, tall spike rush which grows in shallow water with stems reaching 2 m high. It will help stabilise the bank but is not suitable for small ponds. If there is a damp area at the edge of the pond, Carex appressa, tall sedge, which grows to 1.2 m and Gahnia sieberiana, red-fruited saw-sedge, which reaches 1.5-3 m, are suitable. The latter has attractive brown seed heads with small red seeds.

A range of herbaceous semi-aquatic plants can grow in mud or water, which probably dries out in summer. Grasses and sedges include Amphibromus neesii, swamp wallaby grass, which has a loose panicle on erect slender stems to 1 m high with an attractive weeping habit and reddish spikelets; Ficinia lucidus, leafy flat sedge, grows to 1.5 m with shiny dark green leaves and a compound umbel of brown spikes; Isolepis inundata, swamp club-rush, reaches 30 cm in a clump 40 cm across which produces small purplish brown spikes from October to April; Isolepis nodosa, knobby club rush, is very easy to grow and tolerates most situations; Schoenoplectus tabernaemontani, river club rush, has stems terete and grooved to 2 m with a loose umbel-like panicle; Triglochin striata, streaked arrowgrass, is a slender semi-aquatic herb with fine terete or flattened leaves. Two to one hundred tiny greenish flowers appear on a loose raceme up to 20 cm high; and Lomandra longifolia can be planted in better drained ground.

Herbs will provide colour over summer when the water is low. Species include Gratiola peruviana, brooklime, a sprawling perennial herb producing pale pink flowers with yellow throats from October to January; Hydrocotyle laxiflora, stinking pennywort, with round or kidney-shaped hairy leaves. The tiny greenish yellow flowers, which can produce a strong odour, give it its common name; Persicaria hydropiper, waterpepper, an upright glabrous, annual herb with leaves up to 9 cm and a peppery taste; Ranunculus inundatus, river buttercup, a mat-forming perennial with deeply divided basal leaves and smaller stem leaves. Erect flowering stalks hold one to three yellow flowers up to 15 mm wide; Goodenia humilis, swamp goodenia, is a sprawling mat with many yellow irregular flowers from November to March; Mazus pumilio, swamp mazus, a mat of glossy obovate-spathulate leaves with mauve flowers from October to March; and Scaevola hookeri, creeping fan-flower, has small fan-shaped flowers over summer.

A Canberra garden pond in winter. Small or large, ponds provide valuable habitat for insects, birds, amphibians and reptiles Photo: Kathie and Peter Strickland

Shrubs can be planted, if appropriate, to give shelter. Species that grow in a variety of conditions and can tolerate wet and dry soils include Allocasuarina paludosa, swamp she-oak, a small shrub to 2 m with grey-green foliage and brown male flowers May to October. The female cones are inconspicuous; Leptospermum lanigerum, woolly tea-tree, 2-6 m with masses of white flowers September to January followed by woolly capsules; L. myrsinoides, silky tea-tree, a smaller shrub to 2.5 m also covered in white flowers from September to November; Melaleuca ericifolia, swamp paperbark, which grows 2-9 m and has creamy white mini bottle brushes in October and November; M. squarrosa, scented paperbark, grows to 5 m and has stiff dark green ovate to triangular leaves. Terminal spikes of cream to yellow flowers appear September to February; and Goodenia ovata, swamp goodenia, a quick-growing shrub to 2 m which is covered in yellow flowers for long periods.

Kathie and Peter Strickland ran an indigenous nursery on the Mornington Peninsula and have published several books on plants of that area and southern Victoria. Kathie has an honours degree in botany and Peter is an ex-secondary art teacher. Their self published books are: Peninsula Plants and Peninsula Plants V2; Foothills to Foreshore; and The Subalpine Flora of the Baw Baw Plateau.

From the newsletter of the Australian Native Plants Society, Canberra Region, September 2008 (originally published in the June 2008 edition of Growing Australian, the newsletter of the Australian Plants Society, Victoria.)

Australian Plants online - 2009
Australian Native Plants Society (Australia)