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How to build a wicking bed

Aerial view of raised garden bed with seedlings and person wearing red gumboots

To build a 600mm high wicking bed

This clever ‘self-watering’ system ‘wicks’ or draws up water from a reservoir below and delivers to it plants as they need it.

It might sound like magic, but this process is driven by what’s called capillary action. When the soil is near dry, water is pulled from the reservoir and evenly distributed to the soil. This ensures no water wastage and that every drop is used.

 

Note: The maximum depth the soil in a wicking bed should be is 300mm, which is also the ideal soil depth for growing most vegies. You should allow approximately 250-300mm for the reservoir or scoria, so the total depth of the container will be between 500-600mm. For shallower containers, you will need to adjust the height of the reservoir, ensuring the final soil depth is no more than 300mm from the top of the wicking bed.

Steps

1Line the garden bed

Position your chosen container or raised garden bed in full sun and on a level surface. Line the container with a pond liner, ensuring there are no gaps along edges and corners. Check for tears or holes and reline if necessary. Add a 25-50mm layer of scoria in the bottom to help hold the liner in place.

Colourbond garden bed with black plastic insert held by clamps

2Position the pipe

Connect the elbow to one end of the 50mm PVC pipe and position the pipe upright (elbow end down) in a corner of the container – ensure it is easily accessible as this is how you will top up the reservoir. Place a cap on the end of the pipe.

Person fitting PVC section to send of agricultural pipe in a raised garden bed

3Secure and cover the pipe

Attach the agricultural pipe to the elbow and allow it run along or coil along around the centre of the bed. Cover the pipe with 250mm layer of scoria and level.

4Install an overflow valve on the side of the container

Ensure it sits just above the level of the scoria. Drill a hole into the side, make a small incision through the pond liner and insert the poly joiner.

5Cover the scoria

Place a sheet of geotextile fabric over the scoria (this will help prevent soil particles blocking the reservoir).

6Fill the garden bed to a depth of 300mm

Add compost and pelletised organic fertiliser and mix in well. Plant up seedlings, water well from above and apply a 3-4cm layer of organic mulch around the seedlings.

Mulched colourbond garden bed with seedlings and capped watering pipe

7Caring for your wicking bed

You will need to water plants from above for the first few weeks or until plants are established. Newly planted seedlings do not have established roots and are unable to draw moisture adequately from the reservoir.

After a few weeks, fill the reservoir by adding water to the inlet pipe – the overflow pipe will overflow when the reservoir is full. Fill the reservoir up every couple of weeks and this will give you an indication of how fast the wicking bed dries out. Check the overflow pipe regularly to ensure it is not blocked.

Once the first lot of crops finish, top up with new soil and add compost and organic matter. Mix well to help freshen up the existing soil.

Aerial view of raised garden bed with seedlings and person wearing red gumboots

8Don’t want to compromise on style?

We’ve got raised garden beds in any shape, colour and size to fit your yard.

 

Photo Credit: Getty Images

Health & Safety

Please make sure you use all equipment appropriately and safely when following the advice in these D.I.Y. videos. You need to be familiar with how to use equipment safely and follow the instructions that came with the equipment. If you are unsure, you may feel it is safest to consult an expert, such as the manufacturer or an expert Bunnings Team Member.

Grave health hazards are linked to asbestos, which may be in homes built up to 1990. Health hazards may result from exposure to lead-based paints in older materials and copper chromium arsenic (CCA) treated timber. For information on the dangers of asbestos, lead-based paint and CCA treated timber and tips for dealing with these materials contact your local council's Environmental Health Officer. You can also use a simple test kit from Bunnings to indicate the presence of lead-based paint.