Choose plants suited to the site
Identify and select species that are best suited to the site’s soil type, pH and micro-climatic conditions. This will reduce watering needs and ensure the plants have the best chance of survival.
Local knowledge of which varieties perform best in sun or shade is important. Labelling and information about plants is often based on the location where the information was written and the performance of the plant can vary widely depending on the climatic conditions and site. For example a label indicating a plant is suitable for full sun may not be applicable in Perth’s harsh summer.
When in doubt consult local nurseries, horticultural consultants or refer to the Waterwise Plants for WA database.
Use deep rooted species where possible
The main framework of any planting scheme should be of waterwise species. The use of trees is one of the most efficient means of achieving this.
By planting large shrubs, trees and deep rooted plants which are able to be self-sustaining once they are established, water use is significantly reduced over time.
The longevity of larger species also means there is less need to replace shorter lived species with the accompanying high water use required to re-establish greenery at regular intervals.
Note: Where possible, healthy existing trees should be retained. The time lag and water required to re-establish advanced trees is costly.
Wind and sun protection
The use of trees for shade reduces soil and ambient temperatures and provides some protection for smaller plants, as well as aiding passive solar control of buildings and residences.
As part of overall site planning, locate trees so as to provide seasonal shade to garden areas, outdoor entertaining areas and to north and west facing walls of buildings.
Deciduous trees allow winter sun to penetrate while providing shade in summer. Gleditsia for example are a particularly useful genus for this purpose as they shed early and come into leaf late making the most of
the winter sun.
Evergreen trees need to be more strategically placed so that they do not cast shade on living areas of the house and garden during winter. Depending on the size of the structure, taller canopy trees are useful for this purpose, to allow the lower angle of the winter sun to penetrate north facing glass areas of buildings.
Hot, dry winds can cause serious damage to foliage. Protecting plants from wind reduces stress and water use. Trees and shrubs can be planted as a semi-permeable wind barrier. A multi-rowed windbreak, planted in staggered heights if space allows can offer downwind protection equivalent to many time the height of the plants. Screens can be used to achieve similar effects.
Scale of projects
Make water efficient choices depending on the scale and budget of a project. For example, in large scale landscapes use trees, spreading drought tolerant ground covers and hardy native grasses. Keep lawn areas to functional uses only and substitute hardy ground covers or alternative surfaces with shading via trees or other structures.
It is possible to install landscapes using plants that require no ongoing water once established. Obviously native plants, cacti and succulents and hardy Mediterranean varieties are best suited to these style of dry landscapes or xeriscapes.
In the south west these planting schemes are best established in autumn/early winter to make the most of the short wet season.
If unable to irrigate for the first summer losses will occur. This may be acceptable depending upon the scale or nature of the project but ideally water should be provided for at least the first summer for a premium result.
Avoid weed species
Some exotic plants, and many interstate native plants which have apparent benefits in terms of being able to establish and persist with very little water can become invasive.
Avoid selecting species which have weed potential. Many hardy introduced plants have become naturalised and threaten to take over bush land and cultivated areas resulting in huge expense and ongoing programs aimed at containing or eradicating the ‘garden escapees’.
For further information visit: https://florabase.dec.wa.gov.au/
Small garden myth
A recent study by the University of Sydney found that the perception that small gardens were more waterwise could be an urban myth.
According to Associate Professor Basant Maheshwari, ‘Four times the water per square metre is applied to small gardens compared to larger ones’(during a trial where participants were allowed unrestricted use). This is in part due to the fact that many people don’t have a clear understanding of the water needs of their gardens, with plants receiving more than they can use.
There is also the perception that because a garden is small it can be watered more intensively. Over a large area made up of many small gardens this leads to significant overuse.