Wicking Garden Beds

BACKGROUND:

Costa is up to an exciting part of the transformation of the Tembeleski’s backyard.  He is building three raised vegie gardens and he’s using a technique called wicking or self-watering beds.

Wicking beds water plants from below rather than above. This works by filtering moisture through a network of absorption tanks and drainage sand to take water directly to the roots – where it’s needed most. Wicking beds work like a big sand sponge as water moves from the bottom to the top and then wets the soil that the vegies are growing in.

Costa designed these cutting edge gardens for the family from a concept developed by Colin Austin. Wicking beds originated as a way of dealing with erratic rainfall. But by storing water under the soil surface, this reduces evaporation and ensures it’s accessible for the plants when they need it.

BUILDING THE BEDS:

•    Costa has used corrugated iron flat packs with hardwood as the frame for the revolutionary garden bed design. The beds are 3metres long by 1metre wide and about 50cm deep and cost about $550.
•    They look great and are easy to install. Costa had these especially made to suit the space, but there are a variety of off the shelf versions available too. Alternatively, you could do it yourself. Shop around relative to your budget and the materials that will best suit your particular garden.
•    The beauty of pre-fabricated garden beds is that all the hard work of cutting and drilling has been done. All that’s left to do is put two screws in each of the four corners.
•    The next step is to set the beds in position. (Remember that once they are full of sand, soil, and water they are impossible to move around the yard.)
•    Correctly positioning your beds is crucial for a productive garden.
•    Most vegies need full sun for at least six hours a day to grow successfully. However Costa has positioned one bed in half shade for some mint and other vegies that don’t like getting belted in the afternoon heat.
•    To put the beds in place just mark out the perimeter and then excavate the grass from within the bed so that it sits at the right height as well as being perfectly level. Costa has created a 75 mm fall between each of the three garden beds. This is part of the overall design for the backyard whereby the entire site falls from the paved entertainment area down to the sand pit, allowing water to move slowly toward the absorption pit that is incorporated beneath the sand pit, the lowest point on the site.


MAKING THEM INTO WICKIING BEDS:

To make your own wicking bed you will need:

A plastic liner to line the inside of the garden bed framework

Atlantis absorption tanks – Costa used three in each bed, and these were 685mm by 408mm by 450mm.

Atlantis drainage cells

Geofabric – enough to cover the cells and tanks and a layer between the planting soil and sand filter

Some 25mm pvc pipe and elbows to create an inlet to fill the tank and an outlet to allow excess water to overflow and help with circulation.

Washed river sand

A lightweight free draining planting mix

Steps:
•    Line the garden beds with the plastic liner, to prevent any water leakage.
•    You will also need to create two holes at each end of the garden bed: one is to fill the absorption tank and the other is to allow overflow to drain the water out.
•    Remember the absorption tanks form a large part of the wicking bed. These sit on top of the drainage cells and then serve a similar function to a rain water tank under the planting soil. Wicking beds are like a big sand sponge. The water moves from the bottom to the top, moistening the soil where the vegies are growing, in the process.
•    Cover the cells and the absorption tank with geofabric
•    Then add the washed river sand. This is vital for drainage in the bed. And REMEMBER to keep it clean on site because if organic matter mixes with the sand it will completely clog your system and it won’t work.
•    A 30mm layer of sand needs to cover the geofabric and make sure it’s nice and even.
•     Fill the tanks with water and you will know when it’s full because water will pour from the outlet.
•    Next put a layer of geofabric above the sand prior to installing the planting soil, in order to keep the sand filter clean.
•    The next critical part of the planter box is soil selection. A lightweight planter box mix will work best. This is because heavy clay overloaded with organic material will tend to compact. But a lightweight mix will drain freely and allow the wicking to work. The water will draw up from the base and go to the root zone where it’s needed.

COSTING:

All up it cost about $875 to build and plant out one of the three garden beds.


FURTHER INFORMATION:

To find out more about the pre-fabricated frames that Costa used:
HomeGrown Garden Beds
12a Central Coast Highway West Gosford NSW 2250
Ph 0409445477
Email : freeazz@hotkey.net.au
http://www. he.net.au
http://he.net.au/garden-bed-pricing.htm

For information on Colin Austin:
Wicking bed fact sheet correction
www.waterright.com.au


Costa bought the drainage cells and absorption tanks from:

Atlantis Water Management

HEAD OFFICE Sydney, Australia:
3/19-21 Gibbes Street, Chatswood, NSW 2067, Australia
Phone: +61 - (02) 9417 8344,
Phone Australia Wide: 1300 38 28 38              
Fax: +61 - (02) 9417 8311  
Contact Sales: George 

The local landscape suppliers to the Tembeleski Family were:

The Good Soil
98 Victoria St Smithfield NSW 2164
Ph: 02 98766200
Orders:02 96045557
Contact: Tony

Smithfield Building Supplies
901 The Horsley Drive Smithfield NSW 2164
Ph: 97563334

But check the yellow pages or online for a landscape supplier near you.

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