Binh Anson
Due to low rainfalls in Perth, Western Australia, and the surrounding hills areas, resulting in low water storage level in all catchment reservoirs, a water restriction policy has been implemented in Perth this summer. Usage of all sprinkler systems drawing water from the Water Authority's distribution network is banned from 8.00 am to 8.00 pm daily.
John Colwill, Perth's popular gardening advisor, explains the seven principles of gardening that can reduce Perth's thirst for water:
With the introduction of water restrictions, many gardeners fear that they will no longer be able to enjoy their favourite pastime. This is not so. It is possible to have a very satisfying garden which uses less water. Whether you have a well grown garden, or are considering establishing a new one, this leaflet will help you save water.
In the metropolitan area of Perth, approximately 40% of domestic water is used on gardens. By following the seven principles of water saving, it is possible for us to cut this back by as much as 20%, perhaps even more in some cases.
Although restrictions do not apply to bore owners, it is hoped that you too will follow the principles detailed in this leaflet, and reduce the amount of water you use. This will not only reduce your household power bill, but also help to conserve underground water supplies.
Water efficient gardens, like all great gardens, begin on paper. Sketch out a design of the sort of garden you would like. Then show it to a professional who can advise if it suits your needs, and help determine and locate the various components correctly to take advantage of any features of your site, such as soils, shading, wind, microclimate etc. For example, a well placed wind- break of hardy shrubs could dramatically cut down wind problems for you and your garden.
With sound advice, you can develop a plan which fills all of your dreams and requirements but doesn't empty the dams. Once you have such a plan, the garden can be developed in stages, if necessary, according to your resources.
The planning stage is the best time to consider ways of 'water harvesting'. This involves using to good effect in your garden run-off from roof down-pipes and paved areas. Water harvesting can direct water into dry spots such as under-eaves, and can save watering in autumn and spring by making the most of any rain.
Our soils are naturally deficient in organic matter which means they cannot hold much water or nutrients. Improving the organic matter content makes a dramatic difference. It improves plant growth while allowing you to use appreciably less fertilisers and water. Growth is healthier which also means that less maintenance is required.
Organic matter can be added in many ways. You can recycle your own through a composting process and/or buy it in various forms such as peat and animal manures. Commercial soil additives such as soil wetting agents and water-storing polymers will also improve water penetration and retention.
A soil analysis may be helpful to reveal soil factors which can be taken into account when choosing plants. The simplest measurements are pH (whether the soil is acidic or alkaline) and salinity. The Department of Agriculture analyses both of these for A$16 per soil sample. The Chemistry Centre of WA and commercial analytical laboratories also do these tests and others, such as for nutrients.
The type, area and location of any lawn should be carefully considered. Lawns require more water than other areas of garden, and therefore offer most scope for saving water. Lawn areas should be designed and sited to be practical. Lawn should not be used as a 'fill in' material where nothing else could be thought of. Hardy groundcovers are just one of the alternatives that may be used in a difficult area.
Careful consideration of what type of lawn, where it is used, and good management can result in significant reductions in water use costs and maintenance time.
Differing varieties of lawn grass have differing water demands. Cultivars of couch are the most drought resistant. These include 'Santa Ana', 'Windsorgreen', 'Greenlees Park' and 'Wintergreen'. Other warm season grasses such as 'Buffalo', 'Kikuyu' and 'Saltene' have an intermediate water use rate and good drought resistance. Avoid cool climate grasses such as ryegrass, Kentucky Blue and bent grass. These have high water use rates and fair to poor drought resistance. Your local turf supplier or nursery can offer valuable advice on grass selection, establishment and maintenance.
When choosing plants for your garden, it is important to not only consider size, shape, function and appearance, but also to consider how they fit into the overall environment and what resources and care will be needed to maintain their performance. Your local nursery or garden centre can offer valuable advice on all types of plants and their growing habits.
The ever-increasing range of local Australian plants is ideally suited to local soils and climates. Some exotic species from other parts of the nation or the world perform equally well. However, many exotic species need special care and/or extra resources in order for them to perform to their full ability in our gardens.
An added bonus of using local plants is that they encourage the local fauna, particularly birds, to visit your garden.
The ideal watering system is one which will deliver water directly to the plants and then only as much as the plants need. Irrigation systems which simply cover the whole garden area in one operation will result in many plants being given more water than they need. Watering between plants, apart from being wasteful, also encourages unwanted weeds in the garden.
The system should also be capable of delivering a sufficient quantity in a short time to allow the plants to be given a good deep drink. This encourages deeper root growth, greater drought tolerance and healthier plants.
Appreciable amounts of water can be saved through an efficient, well designed irrigation system which should be capable of adjustment to adapt to seasonal changes. Your local irrigation professional can offer valuable advice.
Providing the right amount of water for a plant's needs is much easier when a garden is planned around 'hydrozones'. By placing plants of similar requirements in the same areas, the watering system can he designed to match.
Bare, uncovered soil is a crime in our climate - and the plants don't like it either. Covering the ground with a mulch, which should be topped up regularly to maintain the correct thickness, has many benefits. The mulch assists in retaining soil moisture, discourages weed growth, prevents erosion and evens out soil temperature variations.
Organic mulches have the additional advantage of breaking down over time and feeding the soil. Every part of the garden can be mulched but ensure that the mulch is kept clear of the trunk or stem of any plant to avoid possible fungal problems.
More stable inorganic mulches such as gravel, crushed brick or blue metal can be used to great effect as a landscape feature.
Simply following the principles outlined will bring about a significant reduction in water use and effort, but a water- efficient garden requires regular maintenance to ensure it remains healthy. The irrigation system should be regularly checked, mulches topped up and any new planting should be in line with the planned objective of saving water.
Properly maintained, a water efficient garden is also fertiliser efficient, less reliant on chemicals and much more economical.
More detailed information on the application of these principles to specific plants and/or areas of the garden can be obtained from your Local Government, and members of the following organisations:
* Australian Institute of Landscape Architects (WA Branch)
* Irrigation Association of Australia
* Landscape Industries Association of WA
* Nursery Industry Association of WA
* Turf Growers Association of WA.