SmartGarden Tips

Plant Types and Species

The plant database contains 1,500 of the most common plants in Melbourne and will allow browsing and selection of very general Types such as 'Shrubs' through Categories such as 'Grevillea' to individual species such as 'Grevillea bipinnatifida' (Grape Grevillea). The plant database can also be searched and filtered using keywords and selections. this is useful for identifying individual plants or a range with a specific criteria such as 'low water use'.

Ground covers
Ground covers can be either low or high water need. Low growing natives like correa and grevillea have low water need as do some of the tufting species like agapanthus and dietes. These species often have tough leaves that help reduce their water requirements and many of them will grow well with little or no irrigation. Ground covers with high water need include bedding plants like impatiens and petunia as well as small azaleas. Best performance of these plants requires that they are given extra water over the summer.

Lawn
Lawn can be either low or high water need. Low water need lawns are composed of summer-active grasses and need relatively little water to maintain a green colour. The most common species are kikuyu grass, couch grass and buffalo grass. These all spread by runners and will generally self-repair if damaged. They go dormant in winter with kikuyu grass and buffalo grass generally keeping the best winter colour. Varieties are :

  • Kikuyu grass – no named varieties sold.
  • Couch grass – common, Santa Ana, Wintergreen.
  • Buffalo grass – common, Sir Walter, Palmetto.

High water need lawns are composed of grasses that grow best during the cooler months of the year. Without summer irrigation they go dormant and may die. To maintain a uniform green lawn with these species requires summer irrigation. The most common species are perennial rye grass, Kentucky blue grass, tall fescue, fine (red) fescue, winter grass and bent grass. These are mostly clump-forming grasses and must be reseeded to fill in dead patches. While varieties of these grasses exist, seed for domestic garden use is often not labelled by variety.

Shrubs - low water need Shrubs can be either low or high water need. Typical examples of low water need shrubs include many Australian natives (Grevillea, Correa, banksia, Callistemon, Acacia), diosma, nandina and roses (roses have good drought tolerance but obviously their flowering performance will improve if given extra water). These species often have tough leaves that help reduce their water requirements and many of them will grow well with little or no irrigation. Many of the cool climate shrub species are higher water need and require irrigation to grow well in most parts of the Melbourne area. While these species are generally well-suited to the cooler regions around Melbourne (The Dandenongs, Mt. Macedon) they need extra water in the Melbourne and Geelong suburbs. Typical of this group are rhododendrons and azaleas, smaller Japanese maples, camellias (especially C. japonica varieties) and dogwoods.

Trees - low water need
Trees can be either low or high water need. Typical examples of low water need trees include many Australian natives (eucalypts, Callistemon, Acacia), many oaks and elms, crepe myrtle, Arbutus, olives, claret ash, Canary Date and Washingtonia palms. These species often have tough leaves that help reduce their water requirements and many of them will grow well with little or no irrigation. Many of the cool climate tree species are higher water need and require irrigation to grow well in most parts of the Melbourne area. While these species are generally well-suited to the cooler regions around Melbourne (The Dandenongs, Mt. Macedon) they need extra water in the Melbourne and Geelong suburbs. Typical of this group are birches and maples, Tulip tree, liquidambar, deciduous magnolias and flowering cherries.

Fruit trees
While there are differences in drought tolerance between species, most fruit trees require large amounts of water for best performance. This is mostly due to the large water requirements for good fruit growth. Apples and pears for example are quite drought tolerant as trees, but good fruit growth means that they require high rainfall or irrigation. Low water use fruiting species include grapes and olives.

Vegetables and herbs
While there are differences between species, most vegetable and herb gardens require large amounts of water for best performance. One reason for this is the fact that these gardens are often mixtures of plants and the requirements of the highest water users (lettuce, corn, pumpkins, basil, parsley) sets the demand for the whole bed.

Mulch

Generally, mulch is advocated as an important part of garden water conservation. Mulch reduces soil temperature and reduces evaporation from the soil surface. It can also suppress weeds which compete for water with garden plants.

Our research indicates that mulch will reduce water use in a planted garden bed by about 20% and this factor has been used as part of the model.
You can see this effect by setting up the description of a bed and then checking water use predictions with and without mulch.

Mulch is particularly effective when irrigation is applied under the mulch, for example with drippers. Irrigation or rain that falls on mulch can be trapped by it and not actually get to plant roots. This is especially likely if the rain or irrigation is very light. The kind of mulch has little effect on water use efficiency and so make your choices based on criteria such as appearance and cost. Current thinking prefers coarse textured mulches such as bark chips or wood chips because they can help reduce weed seed germination compared to finer mulches. Remember that organic mulches decompose and may have to be replaced from time to time. Aim to keep a mulch layer between 50 and 75 mm thick.

Conditions - Soil Type, Slope, Plant Density & Exposure

Soil
Soil type is set by default based on the postcode, but this can be overridden when the actual soil is different. The soil type is used to estimate any potential losses from applying water quickly to a low infiltration soil.

To determine the texture of your garden's surface soil you will need a good handful of soil that is representative of your garden. Add water to the soil and work it into a stiff paste in your hand. Ideally the soil should not be so wet that it glistens and dry enough that it stops sticking to your fingers. Work the soil in your hand and force a ribbon out between your thumb and forefinger.

  • Sandy soils feel gritty and only produce short ribbons of up to 10 mm long (see picture).
  • Loam soils feel smooth to tough and spongy and may produce ribbons of up to around 25 mm long.
  • Clay soils are very smooth and sticky to touch and you will be able to produce ribbons of at least 75 mm long (see picture).

Melbourne suburbs can have different soil textures. The Eastern suburbs often have soil with loam topsoils (often these soils are eroded exposing yellow clay subsoil, especially in old orchard areas). The bay-side suburbs typically have sandy soil but areas with clays also exist. The northern and western suburbs generally have clay loam or clay topsoils. In many gardens, soil has been imported to make new garden beds. These imported soils are often sands.
The soil type in your garden will not affect the irrigation schedule that this program provides for you, but it may affect the choice of irrigation system that will work best for you. The low infiltration rate of clay soils means that high application rate irrigation systems may not be efficient, particularly on sloping beds.

Slope
Slope refers to the gradient or incline of the garden area. The slope of the surface of a bed can affect the efficiency of the irrigation system because surface runoff is more likely when the surface is not flat.
Sloping garden beds have to be watered at very low flow rates to avoid runoff, especially in fine- textured (loam and clay) soils. The important issue here is the slope of the surface of the bed rather than the slope of the land on which the bed is situated. Terracing beds on a steep slope will reduce runoff.

  • A steep slope will have a fall or incline of 1 metre across a distance of 4 to 5 metres.
  • A shallow slope will have a fall or incline of 1 metre across a distance of 10 to 20 metres.

Density
A densely planted bed completely covered by foliage will use more water than one more sparsely planted. 'Sparse' plantings will have plenty of space between plants, soil or mulch is visible and there are often gaps large enough to walk through. 'Dense' plantings will have all the surface covered by foliage or may contain various layers of vegetation, such as trees, shrubs and groundcovers. For lawn, select the middle of the range.

The two photographs show a dense and a sparse planting, respectively. Obviously, as a planting grows it can become more dense. In the case of a bed of shrubs, this might take several years. In the case of a plot of vegetables, this might change over the course of a season as the crop grows. Ideally, all the plants in a watering area will have the same water needs, however it is not uncommon to see mixed garden beds where most plants have one level of water use but one or two require more water. This means that where irrigation is being controlled by a timer or similar device the water needs of the entire bed are set by the minority of the plants (or that a few plants get stressed when the others are growing satisfactorily).

Exposure
Exposure refers to the extent to which a garden area is exposed to climatic conditions. A protected area will be cool and shady without much wind. An exposed area will be particularly hot and windy receiving full sun. Exposed areas will require more water.
The extent of exposure of a garden bed can have a great effect on how much water plants use (and hence, how much has to be replaced with irrigation). North facing slopes are hotter and drier than other slopes and will require more water. South facing slopes are coolest and will require the least water. Beds on the south and east side of buildings are shaded in the hottest part of the day and cooler. Tree shade can also affect water use. Use the options that are available to you to change the settings of particular garden beds. Because of this effect, if you want to optimize the opportunities for water savings in a garden, irrigation zones should be set up so that all of a bed is on one microclimate zone.

Watering Systems

Watering Systems

Drip irrigation

The slow delivery of water from drippers to individual plants is potentially very efficient. Losses due to evaporation and wind drift are eliminated. Drip systems are available as individual drippers connected to supply hose or available as drippers embedded within the pipe. Drip pipe with drippers embedded at regular intervals are suited to the wetting of continuous or complete areas of plants. The area wet by the dripper is dependent on the soil type and properties. When used on loam soils the width if coverage is typically in the range of 400 mm to 500 mm. On heavier clay soils the width of coverage may be 600 to 800 mm. Drip irrigation is not suited to sandy soils where water will readily drain through the soil profile. Drip is well suited to installation below mulch and also to installation below the soil surface. Below ground installations require specially designed drip equipment. Drip system performance is dependent on water supply pressure. Regulation of the supply through the use of pressure regulation to ensure drippers operate at correct pressure is advisable. Drip products are available as pressure compensating types which self regulate the supply and provide a constant flow rate over a range of pressures.

In SGW, we assume that you are using about 3 or 4 dripper per square meter.

Sprinklers

Water applied with sprinklers covers large areas. A rotating water stream delivers water at relatively low application rates. This means that reasonably long operation times for example, 30 minutes to 1 hour, are required to achieve optimum irrigation depths. Sprinklers are suited to large lawn areas or situations where distances greater than 10 metres need to be covered. Sprinklers require higher pressure than sprays to operate and are available as portable units, mounted on risers or as pop-up devices. To achieve uniformity of application with sprinklers it is necessary to overlap the coverage patterns.

Sprays

Water applied with sprays is similar to rainfall. All of the plant foliage and soil is wet. Sprays apply water at relatively high application rates and the area covered with sprays is generally a few metres radius away from the spray nozzle. A characteristic of a spray is that the nozzle is fixed (does not rotate) and water is applied continuously to the same area. Sprays are available in many different designs including both on stand pipes or risers and also as pop-up when used to water lawn areas. Irrigation sprays are sensitive to losses and inefficiencies due to wind drift and evaporation losses.

Soaker (spraying) Hose

Water is sprayed out of hundreds of small hose along the entire length of the hose. The total width of coverage is typically 2 to 3 m. The application rate is relatively low. The fine sprays are sensitive to wind and readily distorted.The fine sprays of soaker hoses are not suited to application above mulch as the water can be absorbed by the mulch. Soaker hoses are suited to relatively narrow areas, such as 3 to 5 metres wide, and watering around trees. The supply of water to a soaker hose should be regulated as the distribution from the hose is sensitive to operating pressure.

Microsprays

Water is distributed in fine droplets from small, usually plastic, jets. Typically the coverage is in the range of 0.5 m to 1.5 m radius from the jet. Microsprays are suited to wetting of groups of small plants or watering under the canopy of larger plants, such as trees. The fine spray is sensitive to losses due to wind drift and evaporation. Microsprays require relatively low pressure to operate. If operated at high pressures very small droplets will be formed and the efficiency of application will be low. Whilst microsprays are small the rate of application can be relatively high. The flow rate of microsprays is much higher than drippers and so these two different types of devices should be operated and controlled separately.

Weeping hose

Water seeps out of the hose along the entire length. The area wet by the hose is dependent on the soil type. The total wetted width is typically ranges from around 300 mm for sandy soils to 600 mm for clay soils.To water a garden bed multiple runs of hose should be spaced approximately 500 mm to 800 mm apart. The weeping hose is often constructed from recycled rubber products such as car tyres. The water supply to the hose should be regulated or controlled as the rate of discharge from the hose is dependent on the pressure and flow into the hose. Weeping hose is suited to situations where long narrow areas of garden need to be watered. Ideally the hose should be installed below a layer of mulch or buried within the soil profile. Weeping hose consists of many thousands of very small openings in the wall of the hose, therefore water quality is important. Filtration of the supply water is recommended if water may contain sediments.

Hose

If you are using a hose, it is slightly more complicated because water pressure varies in different locations. Measure your flow rate by calculating how many seconds it takes to fill a (standard) 9 Litre bucket. Your watering time for the area will be: time in minutes = (plant area in sq m) x (seconds to fill bucket) / 60 Note that the selection of a hose assumes the water is applied evenly over the whole plant area.

Automatic Irrigation Systems

An automatic irrigation system will turn irrigation on and off according to information received from sensors and/or timers.

Automatic irrigation systems should be turned off if it rains and the soil is moist. Both rain switches and soil moisture sensors can be used to cancel irrigation.
The operation of automatic irrigation controllers can be cancelled using several different types of control devices. Rain switches can be readily installed so that irrigation is turned off when the rain commences and remains off for a period following the rain. These are reliable and useful. Soil moisture sensors can be installed in the garden and will monitor the soil moisture level at the place where they are installed. Irrigation is prevented if soil is moist. To be effective a soil sensor needs to be accurate, reliable in operation and correctly installed. Considerable care is required to ensure these requirements are met.

Days Between Watering

The number of days between watering is an important factor in maintaining a healthy garden and conserving water. The number of days between watering will be few in hot, dry weather and more in cool, wet weather. In some months the garden will not have to be irrigated at all.

The frequency of watering is one of the factors that determine the total amount of water applied to the garden. The ideal frequency is one where the soil water is replenished after the available water has been removed by the plants. If irrigation is too frequent some water will be wasted. If the period between waterings is too long then the plants will be stressed.

The actual days between waterings is dependent on soil properties, plant root system, water use by plants and the weather conditions. As a general rule, less frequent waterings are recommended, as this tends to encourage deeper root systems.

Watering Depth - why 10mm?

'Watering depth' is the amount of water to be applied at each irrigation. This has been set at a standard 10mm because, almost irrespective of soil type, all the water applied will be trapped in the rootzone of garden plants and is unlikely to run off.

The simplest approach to building the model used to make the calculations for this program has been to base all irrigations (waterings) on applications of one volume of water. Then, the only variation involved is the interval between irrigations. In cooler months this interval will be longer than in hot dry weather.

A 10mm application (10 L/square metre) was chosen because almost irrespective of soil type, an irrigation event of 10mm will be trapped in the rootzone of garden plants. Even in quite sandy soil, this volume of water will not penetrate too deeply and in heavy clay soil it is unlikely to run off if applied slowly. Different types of irrigation systems deliver water at different rates and so by selecting an irrigation system (e.g. drip or microspray) an automatic calculation will convert 10 L to a run-time for that system.

If a gardener wishes to apply larger volumes of water less frequently then as an example, they might be being told apply 10 L of water every 3 days. That is effectively the same as 20 L every 6 days. Remember though that in some soils, applying large volumes of water in one go runs the risk of losses through runoff or deep leaching.

Watering with a hose

If you are using a hose, it is slightly more complicated because water pressure varies in different locations.

Measure your flow rate by calculating how many seconds it takes to fill a (standard) 9 Litre bucket. Your watering time for the area will be: time in minutes = (plant area in sq m) x (seconds to fill bucket) / 60.

Note that the selection of a hose assumes the water is applied evenly over the whole plant area.

Your Suburb / Postcode

The postcode location of the garden is very important and determines the soil and climatic conditions for the garden watering model, specifically:

  • The default soil type used in the calculations
  • The climatic conditions (rainfall & evaporation) used in the calculations
  • The location of the garden on a map for others to view

The postcode is the only factor that must not be changed once set within a garden watering model.

Your Region of Victoria

In order to give high quality watering information for your garden, we have divided Victoria into 18 regions (4 in the suburban Melbourne/Geelong areas, and 14 in Regional Victoria). For each of these regions we have allocated average rainfall, evaporation, and soil-type data. (Click map to enlarge)

The 4 suburban regions are relatively small and hence the data for these are quite consistent across the region. These regions are:

Central Melbourne
Northern Melbourne
Eastern Melbourne
Mountain Melbourne

The Regional Climate Victoria regions are, however, sometimes quite large. The consequence of this is that there will be variation from the assumed average values in climate conditions and soils within the regions. We advise that you check that the soil type that this program displays agrees with what you know your soil to be. This can be changed as you set up a new garden, or from within an existing garden. If you know that the climate data for your particular locality better matches an adjacent climate region than that described by the program, then you might need to change your postcode to that other region.

The areas defined by the regions are as follows:

Mildura Riverland
Northern Mallee
Southern Mallee
Northern Plains
Northern Foothills
Western Plains
West Coast
Cape Otway Coast
Western Basalt Plains
West Gippsland
East Gippsland and Lakes
Far East Gippsland
North East Ranges
High Country