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Wicking beds for vegetables

What is a wicking bed and how can it work in your garden? Angie Thomas explains.



Wicking beds are a clever alternative to growing plants in the ground. They’re a type of containerised garden bed with an in-built water reservoir, allowing plants to draw up or ‘wick’ water from the reservoir below as needed. Just like a self-watering pot, except on a larger scale.

Wicking beds enable healthy plant growth and productive harvests using less water than traditional methods of gardening – there’s no loss of water down into the ground and evaporation is reduced as little surface watering is required. Wicking beds are particularly suited to areas are prone to droughts and water restrictions. They’re also perfect for keeping plants watered while you’re busy or away on holidays for a few weeks.
 

HOW THEY WORK

There are different types of wicking beds, but they all follow the same basic principle: a waterproof container with a lower layer of gravel and water, and an upper layer of potting or growing mix where the plants grow. These layers are separated by geotextile fabric, preventing the growing media from mixing with the gravel below. An L-shaped water inlet pipe is installed to allow the reservoir to be easily filled with water. The principle of a wicking system is that moisture moves up from the gravel layer, through the geotextile fabric and into the growing media where plants' roots are.
 

HOW TO DIY

You can purchase small, ready- made wicking beds or larger DIY kits. Alternatively, make your own using readily available materials. Some people convert a plastic IBC (a plastic tank used for transporting liquids) into a wicking bed, but it’s important to make sure it has only contained food-safe chemicals. Another method is to create a box frame of timber sleepers (similar to a standard raised garden bed) 50-60cm tall. Line the box with thick sturdy plastic – a pond liner is perfect. Care must be taken not to puncture any holes in this plastic otherwise your wicking bed will leak like a sieve! If the surface under the bed has sharp points, it’s important to remove these first or lay some old carpet under the bed to protect the liner.



For the watering tube, connect two pieces of 50mm-diameter PVC pipes with an elbow joint to form an L-shape. The length of the horizontal pipe should be almost the length of the bed while the vertical should be tall enough to reach the top of the timber frame. Drill multiple small holes along the horizontal pipe – these holes will allow water to seep along the length of the wicking bed.

The next step is to carefully cut a hole in the side of the timber frame (and the liner) for a small 20mm diameter pipe – this pipe acts as an kitchen garden {wicking beds } overflow outlet, so the entire wicking bed doesn’t fill with water when it rains. Position the pipe 30cm up the side of the frame, which is where the layers of gravel and growing mix will meet.

Gently fill the base of the lined bed with a 5cm layer of scoria or gravel then place the long part of the L-shaped pipe on top. Cover the pipe with another 20-25cm of gravel. Place a layer of geotextile fabric over the gravel. The fabric stops the gravel and garden mix above from mixing together. Then add a 20-30cm layer of good quality bagged garden mix, which will be the home for your new plants.


MAINTENANCE TIPS

The gravel reservoir is filled with water from the top of the L-shaped PVC pipe. Fill until water starts to drip out of the overflow pipe. Top up the reservoir every few weeks as required.

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Author: WORDS: ANGIE THOMAS