We know plants need water to grow, however understanding when and how much they need can seem like a mystery only “green thumbs” can solve. Enter wicking beds!
Wicking beds are an innovative veggie bed irrigation solution. They minimise the watering challenge by creating a water reservoir that sits underneath the soil your vegies grow in.
A typical wicking bed has a waterproof lining in the bed, on top of which is a layer of small stones. The stones are then covered with water, landscaping fabric is laid on top and the soil goes on top of that. There’s an inlet pipe and a special overflow setup that prevents the water level from rising up into the soil, which would compromise plant health.
The water below the soil layer literally wicks up into the soil, maintaining optimal soil moisture levels at all times (so long as you remember to occasionally top up the reservoir).
How do wicking beds work?
The reason wicking beds work is because of a remarkable characteristic of water: it can move against the pull of gravity using capillary action. Capillary action is water passing through the small spaces between other particles.
To see how this works, dip the corner of a dry paper towel in water and watch what happens. The water moves through the towel, even against gravity. This also happens through the wicking bed reservoir material and through our vegie bed soil.
What’s the catch?
Despite their many benefits, it’s worth knowing that wicking beds use more materials than a standard raised veggie bed, require extra attention to detail when installing and can be damaged (for instance by a tomato stake).
Which crops don’t like wicking beds?
Your wicking beds are prime real estate, especially for edibles that like their water.
Anything that can handle being in the ground and will still produce well (eg. garlic, potatoes, pumpkins, Mediterranean herbs) should be planted into the soil, to save your wicking bed for the thirstier members of your edibles (think leafy greens, brassicas, tomatoes, basil, carrots, etc.).
What you need to build a wicking bed
The key ingredients to a successful wicking bed build are:
- A waterproof container, or a frame that can be made waterproof, ideally using food grade components;
- A liner (depending on the type of container);
- An inlet plumbing setup. For example, 25 mm poly pipe the height of your bed, a barbed 25 mm poly elbow, a short piece of 25 mm poly pipe (about 20cm) and about 1 metre of 50 mm perforated agricultural pipe (aggie pipe);
- An outlet plumbing setup. For example, 25 mm tank valve, 25 mm threaded female-male elbow and 25 mm poly riser;
- Reservoir media;
- Geotextile fabric;
- Good quality soil.
How to build a wicking bed
If you’re keen to give building your own wicking bed a go, check out Issue #11 of Pip Magazine. In it you’ll find a step-by-step guide to setting up your own wicking bed as well as trouble shooting advice. Grab your copy here.