Wicking beds are the brainchild of Queenslander Colin Austin.
Austin claims that “the wicking worm bed is a highly productive growing system which not only produces food from limited water, but also recycles waste organic material to provide plant nutrient and capture carbon”…and my experience with the method, over the space of a decade, confirms his claim.
A wicking bed garden usually comprises a waterproof box with a drainage hole drilled a pre-determined distance from the base. A pipe is inserted into the box which is then filled with growing mix. The pipe is used to add water to the box which drains from the hole in the side when it reaches the correct level.
In practice, the water in the bottom of the box is wicked upward so that the rest of the growing mix in the box is kept moist. This extends the interval between watering. The addition of hollow structures (like sections of PVC pipe), create reservoirs for the water and extend the irrigation intervals even further.
Wicking beds can be constructed virtually anywhere that allows for the creation of this water reservoir…..in ground, above ground or in a wide variety of containers.
Some variations on the theme feature a worm feeding station (a section of 100mm PVC pipe will plenty of small holes will do) which is inserted into the bed. Chopped food scraps (or animal manure) are placed into the feeding station and are converted to plant nutrients by the worms.
They’ve captured my attention for the following reasons:
They save water.
They provide the plants with continuous access to water and nutrients.
They can be integrated with other growing systems including square foot gardening.
They are very easy to water – plants get water from bottom – less fungal disease.
They are simple and inexpensive to build…..and easy to operate.
They will go for days (or weeks) without having to add water. How long they can go depends largely on how much water can be stored in the lower section of the bed.
…..and they would partner beautifully with an aquaponics system.
Wicking refers to the movement of water (by capillary action) upwards through suitable soils (or other growing mixes) – like the movement of molten candle wax along the wick.
Wicking beds rely on the creation of a water reservoir of 75mm – 150mm deep. A layer of soil (or growing mix) is then added – to a depth of 300mm. The wicking action is limited to about 300mm.
At the bottom of the bed, the soil is very wet and at the surface only slightly damp.
Mulch is added to the top of the bed to minimise water loss through evaporation.
Plants should be fed throughout their growing cycle (rather than in one initial hit).
The soil or growing mix needs to be maintained at the correct level for optimum growing conditions. If it is allowed to compact too much, the plant roots become waterlogged.
Polystyrene broccoli or fish boxes are ideal for conversion to wicking boxes – they are cheap, well-insulated and can be set up at a comfortable working height. Fibreglass or plastic grow beds would also make excellent wicking beds.
For those who don’t mind working on their knees, a wicking bed can be constructed in ground using little more than a sheet of builder’s plastic.
One recommended growing mix comprises equal parts of clay, sand and worm castings. There’s clearly some scope for experimentation here. There’s a need for something fibrous in the mix (to assist the wicking action) so compost would be a desirable inclusion and even coco peat might be useful.
Watering your wicking beds from an aquaponics system would provide some nutrients and liquid fertilisers like Charlie Carp or Seasol would serve as a top up.
Overfeeding is a risk in a closed system like wicking beds so you would be advised to feed little and often. Periodic flushing of the reservoir with rainwater would help to avoid problems with the build up of minerals.
Wicking beds demonstrate many of the features of the best growing systems and, as such, they are excellent components in any microponics system.
This article was first published in August 2009. It was reviewed and updated in June 2017.