A self-watering raised garden bed is known as a “wicking bed,” but even though it is a relatively new design that is attracting the interest of many crop gardeners worldwide, it is just a big self-watering pot. The concept of sub-irrigation, in which the water supply rests below the pot and is pushed upward into the soil in the container above, is the foundation of self-watering pots, which have been around for decades. It’s also crucial to keep in mind that a wicking bed is a container garden and that all containers of soil or potting mix/medium have a perched water table, which is a layer of saturated soil at the bottom that never drains away. This layer becomes a wet, anaerobic (without air or oxygen) muck that may promote root infections since it can never dry up due to evaporation or uptake by plant roots.
Wicking garden beds are excellent for places where irrigation is uncommon, including community and school gardens where watering the garden beds during the holidays may be impossible. Depending on the climate, season, and location, the water reservoir in a wicking bed can hold enough water to keep plants alive for up to several weeks. They are particularly helpful for growing around and beneath invasive trees like Australian eucalyptus trees, whose roots savour every last drop of rainfall from the ground.
While using wicking bed systems to cultivate plants is a practical method that expands the types of plants you may grow and the locations where you can grow them, wicking beds also have restrictions, just like any artificial gardening system. You might be wondering what these restrictions are. A wet-dry cycle is necessary for the majority of plants to flourish, however, wicking beds produce a climate where the soil is continually damp, which is unfavourable for many plants. The retention of water in a wicking bed causes fertilizer to build up, and the upward wicking mixed with water evaporation from the soil can cause salt concentrations in the soil to increase to dangerous levels, which can burn plant roots. When surplus salts are present, they build up at the upper soil layers where shallow-rooted seedlings are planted since the upward-moving water also carries them there.
The fact that the soil in wicking beds can only wick moisture so far up through the forces of capillary action, adhesion, and cohesion against the forces of gravity is another problem. The lowest level of soil in wicking beds is always wet while the top layers can be fairly dry. As a result, the depth of the plant roots and the height of the garden bed determine how much moisture is available to a plant. Deep-rooted plants that don’t appreciate “wet feet” (constantly soggy soil) can struggle to grow in a wicking bed because of root rot.
The fact that a wicking bed is a container garden and that all containers of soil or potting mix/medium have what is known as a perched water table, a layer of water-saturated soil at the bottom that never drains away is also vital to keep in mind. This layer can never dry up owing to evaporation or uptake by plant roots and turns into a soggy, anaerobic (without air or oxygen) muck that could encourage root infections.
