For many reasons wicking beds are cool, they are essentially one very big self-watering pot disguised as a garden bed. The idea of a wicking bed is to draw water up from a reservoir below, hence the word “wicking” it moves through the soil and feeds the roots directly. The wicking bed was a system devised by Australian engineer Colin Austin, wicking garden beds and wicking worm beds and they have gained popularity as an awesome water wise garden alternative.
How does a wicking bed work?
Wicking beds draw water up from the reservoir below and operate on the concept of a capillary action, with the soil and plant roots drawing water upwards when required. What this means is, if a wicking bed is properly constructed and maintained the soil should be moist most of the time because the roots access the water as they need too.
What are the benefits of a wicking bed?
- Environmentally they are great for lower rainfall regions or areas affected by water restrictions.
- Wicking beds only deliver water where it is needed (roots) minimising water wastage.
- Wicking beds help reduce the of funky fungal issues.
- Wicking beds are known to be more effective at sequestering atmospheric carbon, than traditional garden beds. That’s a win for us and the planet.
I love wicking beds, outside of the obvious reasons, mainly it is because I am a self-confessed lazy veggie grower. That is because I am mainly time poor so the beauty of this self-watering garden, is it is one less thing I have to think about in high and dry weather. Of course, that doesn’t mean I walk away and forget about it, I still maintain it, I have peace of mind in high temperatures and dry spells that my garden will still thrive.
How do you make a wicking bed?
- Choose a suitable site (full sun for veggies).
- Ensure that it is level, ensuring even water dispersal.
- Overall depth needs to be around 600mm.
- 300mm for reservoir/water zone and 300mm for growing/root zone.
- If you are gardening on soil, dig a hole to a depth of 150mm, ensuring it is level. If it is a closed Wicking Bed System line your container with pond liner or plastic if required to make it water tight. Line the bed with good quality builder’s plastic or pond liner, ensure there are no holes.
- Make sure the sides are in place – or your container has a total depth of 600mm.
- Pour about an inch of gravel or scoria into the bed for the pipe to sit on.
- Install a length of PVC pipe about 50mm diameter vertically, attached to a PVC 90 degree elbow that will sit near the base of the bed on top of the gravel.
- Attach a length of 50mm agi pipe or slotted PVC pipe to the elbow and this will run the length of the bed along the centre.
- Place the cap on the end of the agi pipe.
- Cover the pipe at the bottom of the bed with gravel to a total depth of 300mm maximum.
- Place your overflow pipe at the top of this layer of gravel covering the external end with a small piece of shade cloth.
- Add the geotextile fabric layer (some folk use a double shade cloth – this layer needs to let water up but prevent soil moving down)
- Fill the wicking bed with a good quality well-draining loamy soil with high organic content and mulch well.
- Using a hose fill the wicking bed reservoir using the inlet pipe opening. You can use an old tomato stake for a dipstick to see how deep the water is. Fill the water reservoir until water comes through the overflow pipe.
- Once soil is damp, plant out your wicking bed with your favourite edibles, seedlings or seeds. Sit back, water less and enjoy your wicking bed.
Some things to remember
- Wicking Beds are not a no maintenance garden.
- Left unattended for a long period could very easily turn smelly, sludgy and a salty unproductive mess.
- Ensure the overflow/drainage hole or pipe does not become blocked or non-functional. Give a good clean out every few months.
- Remember that as a closed system, everything you put into the bed stays in the bed.
- It is recommended that greywater not be used in the garden bed.
- Be aware of the fertilisers you use, because overuse may sour the soil rapidly. It is recommended to use natural organic inputs such as Charlie Carp, Seasol and worm juice. In a wicking bed the levels of fertiliser just keep building up in the water reservoir, so it is important to use less fertiliser in such a system and to flush out the whole system from the top to wash out the rising salts and build-up of fertiliser through the overflow outlet, and to prevent the proliferation of any anaerobic pathogens in the muddy soil. Compost and soil will need to be topped up seasonally, as with the mulch.
- One of the most important issue with wicking beds is high salt concentrations in the soil and in the water reservoir. In a wicking bed, plants take up some of the water and some evaporates. As water evaporates, the concentration of salts increases. With any plants, if the concentration of salts in the soil is high enough, water will be drawn out of the plant roots by osmosis, depriving the plant of water and ‘burning the roots’.
- Be aware, when planting that deep rooted plants will have access to the very wet soil at the bottom and the shallower rooted plants may not be able to reach if their roots don’t run deep enough. Deeper rooted plants will run into issues if they don’t like “wet feet”. Most vegetables have around 80% of their roots in the first 30cm of soil so they will survive well in shallow beds.
- Deeper rooted perennials, cane berries, larger shrubs and small trees are not suited to the soil environment created in wicking beds.
- Cover the opening of the pipe with a tile, brick or similar to prevent mosquito larvae and snails from hanging in the tube or garden reservoir.