Wicking beds have become a popular choice for home gardeners, as they offer an efficient way to grow plants in a water-conserving system. However, not all plants thrive in wicking beds, and it is important to know what not to grow in them to ensure the best results.
Wicking beds rely on a water reservoir at the bottom, which is drawn up into the soil via capillary action, keeping the plants hydrated. While this can be beneficial for many types of plants, some are not suited for this environment.
UrbanVeg.com.au have installed and filled hundreds of wicking beds in the greater Sydney area. In this article, we'll take a closer look at the types of plants that we have found are not suitable for wicking beds, and explore the reasons why.
Should you Grow Succulents and Cacti in a Wicking Bed?
One type of plant that should not be grown in a wicking bed is those that require consistently dry soil. These include succulents and cacti, which are adapted to arid conditions and can suffer from root rot if their soil is consistently moist. Wicking beds retain moisture in the soil, making them unsuitable for these plants.
Succulents and cacti are adapted to arid conditions and prefer dry soil. Succulents, for example, have evolved to store water in their leaves and stems, allowing them to survive in hot and dry environments. If the soil around them is consistently moist, their roots can become waterlogged, leading to root rot and other problems.
Cacti have similar adaptations that allow them to survive in hot and dry conditions. Their thick, fleshy stems store water, and their roots are designed to absorb water quickly during times of rainfall. In a wicking bed, however, the soil can become too wet, causing the cactus to become waterlogged and leading to root rot.
Having said that, water only wicks up 35-40 cm in a wicking bed, so if you wish to grow shallow rooted succulents, you can overfill one part of a wicking bed to above this level, and shallow rooted succulents and cacti would grow satisfactorily.
Can Shallow-Rooted Plants be Grown in a Wicking Bed?
Another group of plants to avoid in wicking beds are those that have a shallow root system. Wicking beds tend to have a deep reservoir of water, which can be detrimental to plants that cannot access it easily if the bed is filled too high above the highest point at which water wicks to.
These plants may not be able to access the water they need, leading to problems like wilting and stunted growth.
However at UrbanVeg.com.au, we intentionally only fill our beds 30-50mm above the highest wicking point, so our beds are particularly good with some of the shallower rooted herbs such as basil, coriander and lettuce.
Can Deep-Rooted Plants be Grown in a Wicking Bed?
Tall plants with roots that must go deep, such as trees and shrubs should not be grown in a wicking bed, as their roots will end up in the water system, which may well damage or kill the plant.
That said, plants that don't mind "wet feet" like Tomatoes and Cucumbers can have deep root systems, but that is just in order to seek out water. In our experience cucumbers and tomatoes thrive in wicking beds because of the water availability.
Plants that need to be planted deep, like asparagus are not suited, as the crowns would be too wet at the depth they need to be planted.
Plants With Invasive Root Systems
Our wicking beds provide so much water and nutrition in our special soil mix that we have founds that some plants have invasive root systems that can spread quickly and take over a wicking bed. These plants can also compete with other plants for nutrients, leading to stunted growth and other problems. Some examples of plants with invasive root systems that are not suitable for wicking beds include:
Mint: Mint has a vigorous root system that can quickly take over a wicking bed. It's best to grow mint in a container to prevent it from spreading too much.
Bamboo: Bamboo has a highly invasive root system that can quickly spread and take over a wicking bed. It's best to avoid planting bamboo in a wicking bed altogether.
Horseradish: Horseradish has a deep and invasive root system that can quickly take over a wicking bed. It's best to grow horseradish in a separate container to prevent it from spreading too much.
Plants That Require a Specific Soil pH
Some plants require a specific soil pH in order to grow and thrive. In a wicking bed, the water reservoir is shared across the bed, which means it can be difficult to maintain different pH levels in different parts of the bed, which can lead to problems for plants requiring different levels to other items in the bed.
Some examples of plants that require a specific soil pH and may not be suitable for wicking beds if they are to be grown alongside other plants include:
Blueberries: Blueberries require acidic soil with a pH between 4.5 and 5.5. In a wicking bed, it can be difficult to maintain a consistent pH level, which can lead to problems like nutrient deficiencies and stunted growth.
Azaleas: Azaleas also require acidic soil with a pH between 4.5 and 6.0. In a wicking bed, it can be difficult to maintain a consistent pH level, which can lead to problems like chlorosis and stunted growth.
Potatoes: Potatoes prefer slightly acidic soil with a pH between 5.0 and 6.0. In a wicking bed, it can be difficult to maintain a consistent pH level when grown alongside other crops with different requirements, which can lead to problems like scab and reduced yield. That said, if they are grown alone in the bed we have had good results
So What Should We Avoid Planting in Wicking Beds?
So, while wicking beds are an efficient and sustainable way to grow plants, there are certain types of plants that are not suitable for this environment. Succulents, shallow-rooted plants, plants with invasive root systems, and plants that require a specific soil pH are all examples of plants that may not thrive in a wicking bed. By selecting the right plants for your wicking bed, you can create a productive and sustainable garden that produces healthy and nutritious food.