1. Install the liner: Water is required to sit in the ‘reservoir’ under the soil. Using pond liner or some other non-porous material, line the base and up the sides of the garden bed to the desired height of the reservoir.
2.Create an overflow: If there is nowhere for the excess water to escape after heavy rain the soil will become saturated and will cause the plants to rot. Either drill a hole and fit a pipe at the top of the reservoir/bottom of soil or create your liner in such a way that the excess water simply overflows over the side.
3. Install inlet pipe: An inlet pipe can be installed for quick filling. This will be held in place when you add the reservoir material (Step 4).
4. Make the reservoir: A variety of materials can be used for the reservoir. Stones/pebbles are a popular material, as the water stores within the gaps, but be careful not to put a hole in the liner. Any recycled materials that are strong enough to hold the weight of the soil/plants but will allow water to be stored will work — old crates, ag pipe etc.
5. Add the cloth layer: Geotextile fabric or enviro-cloth works well, as it allows water to flow through but holds the soil above — shade-cloth will also suffice. Lay the fabric layer over the reservoir — ideally you have enough of the cloth to tuck some down the sides of the bed so reaches the lower areas of the reservoir at the sides.
6. Add the soil and plants: Once the reservoir is covered with the cloth layer, it's time to add the soil composition of your choice. A porous loamy soil is best in a wicking bed.
7. Fill the reservoir: It’s now time to fill the reservoir with water. Once water begins to come out from the overflow area, it is full and the soil will begin to wick up to water your plants from below.
8. Water from above for the first week or two, to ensure strong root growth.