There are many ways to create a wicking bed. I chose to make these very simple, economical and easy to construct and maintain mini ones.
Wicking beds are a way of growing plants where moisture wicks up from an underground water reservoir that is below the root zone. This encourages the roots of the plants to grown down deeper rather than staying on the surface. The major advantage of a wicking bed is a significant increase in production, due in part to the soil always being moist, never too dry or too wet, thus causing less stress on the plants. Water evaporation, use and frequency of watering are also greatly reduced.
The simplest and most common form of wicking bed is to have a flower pot standing in saucer of water so the water wicks up into the soil.
This is how I constructed my wicking beds:
I picked up some used vegetable boxes from our local organic shop, then sourced the piping from our local recycle center.
The box is lined with plastic to ensure it holds water. I used a couple of heavy duty rubbish bags. Drain holes were drilled in the larger pipe I used as part of the water reservoir, and an opening created for the filler pipe.
In some of the boxes I used 2 pipes in the bottom to keep the weight of the boxes down for ease of moving them (while the reservoir is dry) at later dates. I then filled the bottom with gravel.
The gravel I used was some I already had. Organic matter can be used instead of gravel, which will have the added bonus of forming a compost tea and feed the plants as well as watering them. If you use wood chips they will reduce the available nitrogen levels so it is best to add extra nitrogen, such as blood and bone. It is best not to use sand around the pipes as it can have a tendency to clog up.
I then placed shade cloth over the gravel to stop the soil falling into the water reservoir.The extra plastic was also trimmed off.
A hole about a centimeter round was made in the side of the box at the level where the gravel and soil meet – the level of the shade cloth. This let any extra water out to stop the box becoming soggy and water logged.
When topping the wicking bed with water you know the reservoir is full when water starts coming out of the drain hole.
Choose a nice, light compost soil with good water retention properties to fill your wicking bed with.
The surface of the bed should be dry. When you plant seeds you can wet the surface, but after they have germinated and developed a root system, you only water from the pipes.
I use a dry bamboo garden stake to dip down the filler pipe to check the water level.