Introduction
Lined wicking beds are an innovative, sustainable gardening approach that provides numerous advantages over traditional gardening practices, including reduced watering needs, improved plant health,
and increased efficiency. This article explains the principles of wicking beds, discusses the key considerations for designing and constructing a wicking bed, and guides you through selecting the appropriate materials.
Understanding the Principles
Wicking beds operate on the principle of capillary action, where water is naturally drawn upwards from a reservoir through a porous material, similar to how water moves up a plant’s roots without the need for pumps, manual labor, or other mechanical action. This effect creates a self-watering system that supplies consistent moisture to your plants, reducing the need for frequent watering and promoting robust growth.
The Importance of the Reservoir
The reservoir is a critical component of a wicking bed, operating as a water storage and supply system. It provides a consistent water supply for the plants, even during hot, dry weather, reducing stress and promoting healthy growth. The enclosed reservoir also conserves water by preventing excess from draining away or evaporating. Since drainage is reduced or eliminated, nutrient leaching is also minimized.
Reservoir Design and Placement
During the design stage, consider the size of your wicking bed and the type of plants you’re growing. The reservoir should be large enough to hold adequate water to supply the plants for an extended period. However, avoid making the reservoir too deep, as capillary action can lift water a limited vertical distance. Therefore, a deeper reservoir won’t necessarily increase the amount of water available to the plants.
Moreover, deep reservoirs with a layer of water that cannot be drawn up through the wicking material may develop stagnant conditions that can harbor damaging microorganisms. A general rule of thumb is to keep the reservoir depth around 8-10 inches.
If a deeper reservoir is needed to support your plants, a separate reservoir can be placed adjacent to and at the same level as the soil to compensate for issues with capillary action. If you choose this configuration, take precautions to protect the reservoir from sun exposure to discourage algae growth and UV degradation.
Choosing Your Location
When selecting a location for your wicking bed, consider the sunlight it receives. Most plants require at least six hours of direct sunlight per day. Usually, a southern exposure (if you live in the northern hemisphere) enjoys the most sunlight.
For in-ground wicking beds, the soil in your chosen location should have good drainage to prevent muddy conditions, waterlogging, and erosion. Avoid areas with standing water. A raised wicking bed mitigates some of these issues, but standing and moving on slippery mud while tending your garden is never pleasant.
It’s also essential to choose a location that is easily accessible for maintenance and harvesting. If you prefer a more private gardening space, consider an area shielded from view or use trellises or other structures to create a private enclosure.
Selecting Materials
Container Options
In above-ground installations, the container should be durable enough to withstand the combined weight of the mature plants, soil, and reservoir. The container’s material should be free of toxic substances that could damage your plants. Depending on the configuration, your container may also need to be resistant to UV damage.
The size of your container should be based on the plants you intend to grow and the desired height of your wicking bed. Larger containers can accommodate deeper-rooted plants and provide more space for growth. However, deep containers may be too tall for an integrated reservoir. An adjacent reservoir can be a good alternative. Keep in mind that very deep-rooted plants may not be suitable for a self-watering wicking bed.
When selecting your container, consider its overall appearance, durability, weather resistance, and insulation properties. Your container should have sufficient drainage holes to prevent waterlogging. The number and size of the drainage holes will depend on the size of your wicking bed and the type of soil you’re using. If you cut your drainage holes, ensure the container material won’t crack or tear. A filtering geotextile or similar material should cover large drainage holes to prevent soil loss.
Liner Selection
Choose a durable, waterproof liner, such as reinforced polyethylene (RPE). RPE is an affordable choice that’s highly resistant to damage from punctures and tears while providing good UV resistance. The liner’s thickness should be appropriate for the size and weight of your wicking bed. 20 and 30 mil RPE liners are generally suitable for wicking beds. The liner should be carefully installed to avoid punctures and tears and secured in place to prevent movement.
Another geotextile layer separates the soil layer from the reservoir to prevent the two from mixing. A nonwoven geotextile is a practical, durable option.
Wicking Material
The wicking material is a crucial component of a wicking bed, as it is responsible for efficient water movement from the reservoir and throughout the soil bed. There are several different design options. Some use vertical wicks that perforate the geotextile layer and run between the reservoir and the soil. Other designs call for filling the reservoir with wicking material, which carries moisture evenly and directly into the soil layer. Studies have shown that a sand/cocopeat combination or cocopeat alone performs well as a wicking material, ensuring consistent and adequate moisture levels in the soil. In this configuration, the wicking material should extend to the bottom of the reservoir to draw up all available water.
Wicking Materials: A Deep Dive
The magic of wicking beds happens in the reservoir, where water is drawn upwards to nourish your plants. But not all wicking materials are created equal! Understanding their properties can make a big difference in your gardening success.
Cocopeat
Made from coconut husks, cocopeat is a popular choice due to its excellent water-holding capacity. It acts like a sponge, soaking up water and releasing it gradually into the soil. Cocopeat is eco-friendly, readily available, and retains nutrients well. However, it is prone to compaction, which reduces its wicking ability over time. Combining it with other materials, like sand or perlite, is a practical option to improve drainage and prevent compaction.
Sand
Sand is another common wicking material, offering good drainage and aeration. It’s affordable and readily available in various grades (coarse to fine). Coarser sand provides better drainage, while finer sand enhances capillary action. However, it doesn’t retain nutrients like cocopeat, so you might need to fertilize more often.
Gravel
Gravel is a durable and long-lasting option, but its larger particle size can significantly limit capillary action. Still, it provides excellent drainage, prevents waterlogging, and helps maintain the bed’s structure. Since it’s less effective at wicking water upwards, especially for taller beds, it’s best suited for shallow wicking beds or when combined with other materials like sand or cocopeat.
Perlite
Perlite is a lightweight, volcanic glass material that improves drainage and aeration in the wicking bed. Mixed in the soil, it prevents compaction, promotes healthy root growth, and enhances water distribution. However, it can be more expensive than other options.
Synthetic wicks
These include materials like fabric wicks or ropes designed to draw water upwards. They offer controlled water distribution and can be effective in specific wicking bed designs. However, they may not be as durable as natural materials and can be prone to clogging.
Soil Mixture
Select a soil mix rich in organic matter and with good drainage properties. Amend the soil with perlite or sand to improve drainage and prevent waterlogging. A mix containing perlite, vermiculite, or cocopeat will help retain moisture in the upper soil layers so that moisture levels remain consistent throughout the soil layer.
Drainage Layer (if necessary)
Suppose the soil around an in-ground wicking bed is prone to waterlogging. In that case, you can add a layer of gravel or sand beneath the liner to improve drainage. This will prevent water from collecting below the liner and causing it to shift or bubble up.
Conclusion
Like most gardening projects, designing and building a lined wicking bed requires careful planning and material selection. By leveraging the fundamental principles of wicking beds, your new labor-saving garden can provide a trouble-free, satisfying experience.
The following article will describe the step-by-step process of constructing your wicking bed. Stay tuned for detailed instructions on preparing the container, installing the liner, adding the wicking material, and planting your plants.
