When you have a polytunnel, you will always find that the space quickly fills up. Finding new and innovative ways to grow more and increase yield in the space you have available is important. A wicking bed is one interesting type of growing area that you might not have considered. In this article, we’ll delve a little deeper to learn what a wicking bed is, and why you should considering having one in your polytunnel. You’ll also discover some tips to help you make one, if you are thinking about this option for your garden.
There are a range of interesting and innovative growing solutions that can boost productivity and increase the quantity and perhaps even the quality of what you can grow. Many of these revolve around the careful and clever use of water. When we think about how water moves around, we can develop clever new methods for growing our food. When we think about how we can use it more wisely, we can reduce the amount of this precious resource we use. We can harness it more effectively to grow our produce.
A wicking bed is one solution that uses water wisely and well. It can be an effective way to reduce water use and, potentially, increase the size of our harvests. But what exactly is a wicking bed? Read on to find out more.
What is a Wicking Bed?
Wicking beds are traditional raised beds filled with dirt that sit on top of a reservoir of water. This reservoir of water can be part of a hydroponic or aquaponic system. It can also simply be fed from a rainwater harvesting system on our polytunnels, or from the roofs of our home or other garden structures. You can also make a wicking bed with a reservoir that can simply be topped up by hand with a watering can.
The idea of a wicking bed was devised by Australian inventor Colin Austin. The system is designed to increase food production while using around half the amount of water that a more traditional irrigation system would use.
Rather than watering plants from above, a wicking bed waters plants from below. Water is drawn up through ‘wicking’ or capillary action through the growing medium from the water reservoir in the base of the bed. This provides the plant roots with the water they require, and less is lost to surface evaporation.
A Wicking Bed’s External Structure
A wicking bed can be made in a wide range of raised bed structures, planters or containers. As long as the base can hold water, you can use a number of different reclaimed items and materials. For example, you might:
Repurpose a large plastic storage container for the purpose.
Use a half of a reclaimed plastic barrel/ rainwater butt set in the soil.
Built raised bed edging from natural/ reclaimed materials and line the inside with plastic sheeting (perhaps you could use leftover polytunnel cover material for the purpose).
A lined wooden crate or box made from reclaimed wood.
A reclaimed metal trough or container.
The Water Reservoir
The water reservoir in the base is usually made by placing gravel/ stones in the base. You might even be able to source these from your own garden. Just rinse off garden stones in water to clean off the soil, then you can place them in the base of the container or bed you have created.
Of course, you will also have to place a pipe to get the water into this reservoir. Commonly, a piece of old PVC pipe is used. A section of pipe with holes drilled in it lies along the base of the bed or container, then it turns at a right angle and a section of unperforated pipe runs vertically up and out of the container or bed.
You might also use a section of drainage pipe or similar, or a section of drip irrigation hose attached to a hosepipe, which is in turn connected to an existing rainwater harvesting system. It does not matter how exactly water reaches this reservoir, as long as it can continue to do so once you have filled in the growing medium on top.
Since you will be placing your growing medium on top of this reservoir of water, you also need to make sure the water reservoir does not get clogged up. Once the pipe and gravel/ stones are in place, you need to make a water-permeable barrier of some kind to stop soil/ organic material from dropping down into the reservoir and clogging it.
Fortunately, there are a number of things that you can use for the purpose. For example, you could use old hessian sacking material, old bedding, old rugs or other sturdy household fabrics etc.. So you may well already have something suitable that you could use.
The Growing Medium
Now all that remains to finish your wicking bed is adding your growing medium. A good mixture of soil and compost will definitely get you off to a good start. But you can also use layers of organic material to built up the layers to compost in place. You can do this in the same way that you could do when filling any another other raised bed.
You can add thin layers of nitrogen rich (green) and carbon rich (brown) materials to build up the growing medium to the required depth. This is the same thing you would do when creating a traditional compost heap. Use this ‘lasagna bed’ method and you could make use of things you already have, if compost/ good quality soil is in short supply.
When you use this method, the efficacy of the wicking bed will increase over time. You may have to water from above initially, but as the materials break down, the wicking process will improve and you should have a bed that you can use (replenishing material with top mulching) for many years to come.
Why Have a Wicking Bed in Your Polytunnel?
As mentioned above, a wicking bed can substantially reduce the amount of water that you use when watering your plants. By feeding your wicking bed from a rainwater harvesting system, you can create a clever and resilient system. One that will use far less water over time, and which can be managed sustainably.
Fewer Worries Over Watering
By getting clever about how exactly you link your wicking bed into water systems, you could also create a polytunnel growing area that can be self-watering, and which will survive even when you are very busy or away from home. So adding one in your polytunnel could make it a more low-maintenance growing system.
Since roots will wick exactly as much water as they require, the need for you to carefully monitor how much water you provide will be reduced. You won’t need to worry about over-watering or under-watering your crops.
Potential for Growing More Crops in a Hydroponic System
A wicking bed’s pipe and reservoir can be linked to a hydroponic system. This means that you can integrate it into either a hydroponic (growing plants in water). Or in an aquaponic system (hydroponic systems including fish to fertilise the plants). These systems can be used to increase yield in a polytunnel garden.
There are a wide range of plants which can be grown directly in water. But there are other plants which do need a soil-based growing medium or other growing medium. Adding a wicking bed to such a system, therefore, increases the number of edible crops that you will be able to grow. This type of bed can allow other vegetables to be grown as part of a hydroponic or aquaponics setup that could not be grown in other media or using other methods within these systems. A wicking bed can be used to grow potatoes and other tubers. You could also grow root crops, such as carrots and parsnips, for example.
Increased Yield with a Wicking Bed
Gardeners often find that providing the exact amount of water that plants need can increase their yield. By meeting the water needs (and nutrient needs) of plants more closely, such a system can lead to healthier and stronger plants. The healthier your plants are, the more likely they are to produce prolifically. So a little effort to make a wicking bed could lead to a better harvest later in the year.
Do you have one or more wicking beds in your polytunnel? What did you use to make them? How do you fill their reservoirs? What do you grow in them? And how well do they actually work in practice? Share your experiences, comments, tips and suggestions below. This could help others work out whether a wicking bed is the best idea for their polytunnel.
Elizabeth Waddington is a writer and green living consultant living in Scotland. Permaculture and sustainability are at the heart of everything she does, from designing gardens and farms around the world, to inspiring and facilitating positive change for small companies and individuals.
She also works on her own property, where she grows fruit and vegetables, keeps chickens and is working on the eco-renovation of an old stone barn.
To get in touch, visit https://ewspconsultancy.com.