Irrigation (Gardens) BHT210


  • Study, learn, and better manage the water needs of a garden
  • Flexible 100 hour course for gardeners, horticulturists, landscapers

Water is essential to plant growth and is often the major limitation to productivity. However, depending on the climate, the value of the plant, the value of the land and its suitability for irrigation, the cost, reliability and quality of the water supply, irrigation may or may not be possible or feasible.

The main objective of irrigation schemes or systems is to produce a particular desired pattern of plant growth. Maximum vegetative growth does not necessarily correspond to maximum yield of the part of the plant desired e.g. fruit, nuts, or roots.

In addition, achieving maximum yield may require inefficient use of available resources, whether it is land, water, equipment, or labour. 'Optimum yield' is usually the desired objective.

This has been defined as the yield at which the benefit/cost ratio is at maximum, although even this may be hard to achieve if any of the resources required for the irrigation system e.g. land, water, or equipment is limited. Therefore, it is important to clearly define the purpose or desired outcome of an irrigation system

There are 10 lessons in this course:

  1. Introduction to Irrigation
  2. Soil Characteristics & Problems
  3. Estimating Plant Needs & Irrigation Scheduling
  4. Drainage
  5. Types of Irrigation Systems
  6. Trickle Systems
  7. Design Specifications
  8. Pumps & Filters
  9. Selecting the Right System for a Plant
  10. Design & Operation of Systems.

Each lesson culminates in an assignment which is submitted to the school, marked by the school's tutors and returned to you with any relevant suggestions, comments, and if necessary, extra reading.




Water use has become unfortunately a subject for talk due to drought and water restrictions. Also, in any normal summer, we need to be water wise to care for our garden properly without wasting a precious resource: water.
In summer, plants will need more water. It is also easier to use water incorrectly at this time of the year. Naturally you will need to water your plants more often when it is hot but good watering involves more than turning on the sprinkler every couple of days or standing around with a hose each evening.

The do’s and dont’s of watering

  • Water early in the morning – the water will have a chance to soak deeply into the soil before the sun gets too hot, and water on the foliage will have evaporated before the hottest part of the day reducing the risk of foliage burn.
  • Water in the evening – this is a pleasant relaxing activity that can benefit your garden and your health. Be careful not to moisten leaves, but just the soil, as that encourages fungal diseases on plants. The water droplets remain on the plants overnight, providing the perfect conditions for the spread of many common fungal diseases, including black spot on roses. 
  • Avoid watering in the middle of the day – some foliage burns in strong sunlight if water remains on the plant. African violets, gloxinias and newly planted seedlings are particularly susceptible to foliage burn. Also, water evaporates before reaching plant roots, so you are wasting water!
  • Do water deeply – this encourages the roots to grow downwards, giving a healthier and stronger plant. This reduces the likelihood that the plants will suffer from water stress, particularly if you are unable to water for a few days in very hot weather or if you are away on holidays. If you spray plants lightly with water each day, the water is unlikely to penetrate down to where the roots need it. Over time, the roots will only grow in the top couple of centimetres of soil, where they are subjected to the extremes of heat and cold. 
  • Add plenty of organic matter to soils before planting. This helps improve soil structure allowing better water penetration into the soil, as well as improving the ability of the soil to hold water. Organic matter also provides some nutrients, and encourages the growth of a healthy soil-root system (rhizosphere).
  • Use mulch – this will make a big difference to the amount of water you need to apply. Evaporation of water from the soil can be reduced by up to 70% or more. Be careful though, that you do not use too thick a layer of mulch, as the mulch can act like a sponge when you water soaking up a lot of water preventing it from reaching the soil beneath. Some mulching materials, particularly fine materials such as sawdust, can also pack down creating a barrier to water penetration. Use a mixture of coarse and fine materials, and periodically check, using your fingers, to see if the water is penetrating the mulch. 
  • Think about installing a drip irrigation system. Micro-jets and drippers use much less water than sprinklers and hand watering. 
  • If you are going to use a sprinkler, use one that produces large drops rather than fines ones which are more readily blown around in the wind, and are more readily evaporated.
  • Take care when applying fertilisers dissolved in water in summer, as they are more likely to burn the foliage in hot weather.


  • When doing modifications to your garden, consider landscaping with drought resistant or low water requirement plants, like in xeriscaping.
    • Group plants with similar watering requirements together. This allows you to only provide the amount of water the entire group require, rather than providing only for the most water-hungry plants.
  • In summer and during drought, avoid cutting your lawn too low (less than 2-3cm), as higher grass will shade the soil, protecting it from drying out too quickly. Cutting too low may promote grass burning.
  • Use timers on irrigation systems to ensure they are turned off in case you forget that they are on.
  • Use soil moisture detectors or rain detectors connected to your watering system so that when it rains, the system doesn’t turn itself on additionally. That will save water too.
  • Use a water wise press-and-release hose nozzle, so that when you are not watering the hose automatically shuts off.
  • Fixing, or replacing worn or leaky hoses, nozzles, sprinkler heads, timers, etc. can save quite a lot of otherwise wasted water. 
  • Use a broom and shovel to clean your hard surfaced areas (eg road gutters), rather than washing them down with water from a hose (which can waste more than 1000 litres of water per hour).
  • Create windbreaks using plants or permeable materials such as trellis, or picket fences to reduce the effects of drying winds.
  • Don’t over fertilise your plants, including lawn. This encourages a lot of growth, which increases the water needs of the plants, and results in soft growth that is more easily damaged by pests and diseases, mowing and/or harsh conditions.
  • Add wetting agents, there are many brands available that offer ecological and petrochemical derived granules, to your lawn and garden beds. This helps improve water penetration and retention into and through the soil, reducing water loss through evaporation and runoff. Be careful handling it, as some of them may be irritating to your respiratory system when inhaled.
  • Soil wetting agents, and water storing granules, can be added to potting mixes to reduce the need for watering pot plants. Be sure the size of any container is suitable for the plants in them. If the container is too small, they will require very frequent watering. If the container is too large then you might be wasting water (the plant roots only fill a small amount of the media in the container). Pot plants can also be lightly mulched to reduce evaporation losses from the media.
  • Reduce the amount of lawn you have by replacing it with beds of plants with low water requirements or with soil cover plants, or choose lawn species that have good drought tolerance. Reducing the need to water your lawn can save you considerable amounts of water. You can also allow your lawn to “brown off” during hot, dry conditions. It will generally regrow very quickly once conditions improve (higher rainfall, cooler temperatures).
  • Use part circle (e.g. quarter, half, three quarters, or adjustable radius) sprinkler heads to reduce waste from watering areas that don’t need it (e.g. paved areas).
  • Selective pruning of very leafy plants after the spring growth flush can reduce the water needs of the plant during summer (the less foliage the less water lost through the leaves). This need to be done carefully to avoid damage to the plant, but in a dry weather spell it could save your preferred plant’s life. If the plant flowers in two year old growth be careful not to cut one year’s growth, otherwise you won’t have any flowers the following season.


One of the biggest problems in gardening is not watering when it is needed. Not only can plants suffer from not enough water, they can also suffer when they are watered too much and too frequently.
You can measure soil moisture quickly with some simple and inexpensive mini moisture tester that can be bought through internet shopping or in DYI and gardening shops. Another simple technique is finger testing: pushing your finger into the soil can help determine if the soil needs watering. If the finger comes out dry then it most probably is time to water. If the finger comes out moist and cool, then it could forgo the watering till a little later!



 A great course for:
  • Gardeners
  • Those working in garden centres
  • The home gardener
  • Landscapers
  • Garden Designers
  • Home owners


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Fee Information (S2)
Prices in Australian Dollars

PlanAust. PriceOverseas Price
A 1 x $781.66  1 x $710.60
B 2 x $416.96  2 x $379.05

Note: Australian prices include GST. 

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