Thursday, 22 January 2015 10:27:52 AM Australia/Sydney
How to build a water wise garden
Half of household water use is in the garden, and with this MitrePlan you can create a beautiful, rewarding garden that requires minimum water. You could even create a garden that collects water for later use!
- Step 1: Design For Low Water
- Step 2: Water Saving Plants
- Step 3: Reduce Water Loss
- Step 4: Collect Water
- Step 5: Water Wise
- Garden edging
- Top soil, clay breaker, wetting agent, pH adjuster
- Potting mix
- Mulch, compost, compost bin
- Garden ties
- Hose and fittings
- Tape measure, pegs, string lines
- Spade, fork, barrow, garden trowel
- Secateurs, shears
- Hedge trimmers
- Pruning saw
- Watering can
Step 1: Design For Low Water
The garden with lowest water use would be one with no plants at all, right? Not necessarily. The natural world doesn’t need people to water it, and that’s the hint. Check out the natural bushland near your home and have a close look at the types of plants growing together. Observe both the species and the shapes and sizes of the plants. Observe how they grow together – their spacing, the protection they provide each other, the mulch on the soil surface, and so on. Take a few pictures so you can later identify the species and think about application at home.
Depending on where you live, you should be able to identify native plants suited to the local conditions, and perhaps some introduced plants that thrive locally without the help of people.
Some plants need lots of regular water (such as impatiens), some barely any (such as cacti). By grouping plants with similar thirst you can reduce your water use because you don’t have to water the whole garden just to cater for the most thirsty plants. Water the thirsty ones when they need it, and the others less often.
You will have noticed the huge difference in temperature when you are in the shade of trees, compared with being out in the open sun on lawn or bare ground. Have you also noticed the difference between tree shade and roof shade (say under a pergola with a sheet roof)? The tree shade is generally more comfortable, so imagine the effect on plants that live under the protection of trees.
It can be a complex issue, as some plants require full sun (most vegetables), so you may need to carefully plan the location of taller plants to the south of shorter ones that need full sun.
By covering the ground with a living “coat” of layers of plants at different levels you will reduce evaporation, create a more consistent ground temperature in summer and winter, and create a more healthy environment for other living creatures (such as insects, frogs, birds and lizards) that generally assist with plant health.
Get some advice from your friendly local Mitre 10 garden centre staff.
Step 2: Water Saving Plants
There are thousands of plants available that could be classified as “low water use”. We’ve listed just a few here. Many of these are Australian natives.
- Common Everlasting
- Creeping Boobialla
- Grevillea poorinda 'Royal Mantle'
- Purple Coral Pea
- Snow In Summer
Small shrubs/Grass to 1m
- Correa 'Dusky Bells'
- Dwarf English Lavender
- 'Miniature' or 'Dwarf' Twiggy Baeckia
- Spiny-Headed Mat Rush
Medium Shrubs over 1m
- Australian Indigo
- Common Emu Bush
- Common Rosemary
- Long-leaf Waxflower
- Native Rosemary
Tall shrubs over 2m
- Adam's Needle-and-Thread
- Banksia ‘Giant Candles’
- Lilac Hibiscus
- Scarlet or Lemon Bottlebrush
- Black She-Oak
- Coast Banksia
- Crepe Myrtle
- Hop Bush
- Yellow Gum
Step 3: Reduce Water Loss
Water is wastefully lost in two ways: evaporation and runoff.
Water on the surface of soil and pavement will generally evaporate fairly quickly. Obviously you should avoid watering your driveways, pathways and buildings.
Water that does land on the soil should soak into it quickly and deeply so it will be available to plants and not lost to the sun and wind. Natural topsoils are generally poor in Australia because they were very thin anyway and have been lost through building and farming activities. To create topsoil with good drainage you’ll need to break down clumpy, solid soil (such as clay) with an additive such as “GroundBreaker”; and dig in large amounts of compost. Organic material added to the soil will improve water absorption straight away, but most importantly, it will encourage populations of worms and other subsoil creatures that will do even more for soil drainage and plant nutrition over the long term.
Create the deepest possible topsoil, and continue to compost waste from your garden and kitchen to replenish the soil on an ongoing basis. Nature reduces evaporation by covering the soil with plants, plant litter, or preferably both. You should do the same. Regardless of how closely plants are spaced, cover the soil with about 75mm of mulch. Many materials can be used, including compost, leaves, wood chip, bark, straw, coconut or sugarcane fibre, or even pebbles. The purpose of this layer is to insulate the soil from the sun and wind, but it fulfils many other functions, including providing a habitat for many creatures that again provide nourishment for plants.
Depending on the plants you intend to grow, you may also have to adjust the pH (acidity or alkalinity) of the soil. See our other “Grow It” MitrePlans for information.
Runoff can occur for many reasons, mostly because pavement is watered, but often water will “bead” on top the soil and runoff without soaking in. Soils can become hydrophobic (repellent to water) and can be remediated as described above, or they can be treated with agents that will help them to take water in. These agents are essentially detergents, such as EcoWet, and they’re specially designed for the job.
Step 4: Collect Water
Roofs are efficient water collectors just waiting for you to exploit. Check out our MitrePlan “Install a Water Tank” for more information. You can collect and store water from houses, sheds, carports, and pergolas – even on the tiniest of blocks.
The roof of your house isn’t the only rain-collector available to you. The ground itself receives the same amount of rain, so think about how much water the soil can absorb, and how you can drain pathways and paving into the garden beds and lawns.
The average household produces 400 litres of greywater per day. If you can use it all to replace drinking water that you would have used for watering plants you could save around 140 thousand litres of drinking water every year!
Greywater is the waste water from showers, baths, spas, hand basins, laundry tubs, washing machines, dishwashers and kitchen sinks (although kitchen water is generally too contaminated).
Wastewater (otherwise known as sewage) entering the sewer system is classified as either blackwater (grossly contaminated by human faeces and urine) from toilets and bidets; or greywater (not grossly contaminated, but otherwise not considered drinking quality).
You can re-use any wastewater from your home, but blackwater must be treated by an approved sewage treatment facility before the water may be legally used for any other purpose.
Before you spend too much time and money on diverting greywater, check with your local authorities (see your water bill) to find out what you can and can’t do.
If you stick to the guidelines you can save large amounts of water and money, keep a green garden, and know that you’re doing your bit for the environment.
See our MitrePlan “Greywater” for further information.
Step 5: Water Wise
Water on the surface of the soil will generally evaporate before plants can make use of it, so be a little inventive with methods of introducing water deeper into the soil.
Send It dDwn
If you are renewing gardens and lawns you should consider installing perforated agricultural pipe (ag pipe for short) to use as a deep watering system as well as drainage. You may have seen councils use them as a method of deep watering the trees that grow in the tiniest holes in street pavement.
You can connect these pipes to your stormwater system in a variety of ways, depending on your home’s specific situation. For example, you might want to connect them to the overflow pipe from your water tank, so the tank fills first, then water flows deep into the ground, then water flows to the stormwater drains. Ironically, stormwater drains once did send rainwater down into “rubble” pits in the ground, where it would disperse over time. These proved to be problematic over time, so the practice switched to sending rainwater straight into the street gutters. You may need to replace your ag pipes once they become invaded and choked by tree roots.
You can also water deep down with your hose by using a “Water Spike”. It is simply a long metal tube with a hose connection. As you push down on the spike, with the water running, it easily penetrates deeply into the soil.
Cut the bottoms off plastic drink bottles, remove the lids, and bury them at least half-way down in the soil next to a plant. Fill the bottle when you water the garden and this little reservoir will trickle-feed the plant for 24 hours or more. Even easier, buy a set of watering spikes and attach the bottles to them.
Spray and sprinkler irrigation systems waste water by atomising it so that much of it is evaporated before it even reaches the ground – especially on hot or windy days. Install drip irrigators instead, and completely cover them with mulch. In this way virtually no water will be lost to evaporation, but monitor water flow and timing to ensure water isn’t wasted as runoff.
Subsurface irrigation is another wise way to water. Porous pipes, such as “Aquapore” may be laid in the soil to provide a gentle, steady flow of water. Another type of subsoil irrigation is “capillary watering” such as “Magic Carpet”.
If you use an automated irrigation system you can install a moisture detector in the soil. If the soil is already wet (such as after rain) the detector will not allow the irrigation to be switched on. Any irrigation system connected to mains water must be connected by a licensed / registered plumber and include a backflow prevention valve.