Wicking refers to water moving in soil, like melted wax in a burning candle, through countless invisibly small channels called capillaries. With the right soil wicking can draw water upwards to 300mm.
Wicking Boxes and beds
Any containers that are waterproof or can be made waterproof by a plastic liner can be used for wicking. It needs a water reservoir at the bottom in the box or bed with a fill pipe to surface through. An overflow pipe through the plastic and the wall keeps the water level at 100 mm from the bottom. It also drains excess rain. Mulch on the surface minimises evaporation.
Why Use Wicking Beds and boxes
They are a very efficient way of using limited water and time. The liner prevents water from percolating below the plant root-zone and stops competition for water from nearby plants and trees. Having a water reservoir in the bed or box means that watering can be done mainly on weekends. Soils can be mixed to suit the plants, see Soils for wicking boxes and tubs.
Styrofoam boxes
Styrofoam wicking boxes can be put on tables for ease of working. They are low cost, simple to make and maintain, and can be used anywhere, even on balconies and patios. They are transportable and can last for more than ten years if handled with care. The boxes are often available for free from greengrocers or vegetable wholesalers.
See Making a Styrofoam wicking box.
Wicking tubs
Larger plant pots and tubs can be converted into wicking pots and tubs by lining them with plastic and putting in a reservoir, fill pipe and overflow. Black tubs can get very hot and putting shade cloth around them helps to keep the temperature down.
Wicking beds
Wicking beds are made in many shapes and sizes and from many materials as shown in the [[Wicking – Gallery]].
Watch Out
A very common and widely promoted mistake is placing bark or stones next to the reservoir and a plastic liner or cloth above it for fear of soil being washed into the reservoir during rain. That does not happen. But it stops the wicking, wastes space and negates the whole purpose of making the beds or boxes. For an explanation see No plastic liners, bark or stones in wicking beds, tubs and boxes.
