Growing Hydroponically in a Polytunnel: Maximising Vertical Space for High-Yields
Hydroponic growing is transforming the way we grow food. By growing plants in a soluble solution, the need for soil is eliminated, which opens up the opportunity for growers to not only make use of the surface area of their polytunnel, but also the height – creating a vertical garden. Combining hydroponic systems with a polytunnel creates an environment for year-round growing, offering protection from unpredictable weather and optimising growing conditions. Whether you’re a smaller scale operation, looking to grow food for your family, or you’re looking to grow on a commercial scale, introducing hydroponic growing structures can help maximise your growing capacity.
In this guide to growing hydroponically in a polytunnel, we’ll take you through the essentials to know about growing food hydroponically, showcase the benefits of vertical hydroponic farming options, discuss what crops grow well hydroponically, as well as guide you through the best nutrient practices and choosing the right growing media for your crops.
Polytunnels & Hydroponics: Why they work
If you’re new to the world of hydroponics, let us first discuss exactly what hydroponics is. Hydroponics is a method of growing that isn’t reliant on soil. Instead, crops are grown either directly in water or in an inert medium such as coir, delivering both the nutrients and water your plants need to grow, directly to their roots. As this is a more controlled method of delivering nutrients to the crops, some plants grow faster than they would if they were sown directly into the soil. Plants such as lettuce, asian greens, tomatoes, herbs, capsicums, cucumbers and strawberries all do particularly well when grown hydroponically.
Although you can choose to grow hydroponically outdoors, growing inside a polytunnel offers more control, protection, and efficiency, leading to better results for your hydroponic system.
Benefits of growing hydroponically in a polytunnel
Weather Protection
Inside a polytunnel, your crops are protected from harsh weather events such as heavy rain, strong winds, and extreme heat or cold. This means more stable growing conditions, leading to healthier plants (not to mention improved longevity of your hydroponic equipment).
Pest & Disease Control
Polytunnels help reduce pests like insects and birds from taking hold of your crops, reducing reliance on pesticides and insecticides. It also reduces exposure to wind-borne diseases that can be detrimental to your crop.
Year-Round Growing
In a controlled environment, like a GROW Tunnel, you can extend your growing season and, depending on the crop, potentially even grow year-round. The polytunnel structure traps heat and light, creating a warmer growing environment indoors during the colder months. In summer, shade net and exhaust fans can help control the temperature in your polytunnel, and protect your crops from overheating.
Water Efficiency
Using hydroponic systems inside a polytunnel reduces evaporation caused by the sun and wind, making them even more water-efficient at recycling the water used in the growing media.
Maximising Space
In a structure like a polytunnel, you can set up vertical systems, which let you grow plants in layers, increasing your total yield.
Nutrient Solutions: The Key to Successful Hydroponic Growth
One of the biggest concerns when growing hydroponically is the nutrient solution. In a soil-based system, plants receive nutrients from the soil, but in hydroponics, you’re responsible for providing the right balance of nutrients. Getting this balance right is essential for healthy plant growth.
The most effective way to manage nutrients is to use hydroponic growing nutrient solutions specifically designed for your crop. These solutions will include the right ratios of nitrogen, phosphorus, potassium, minerals and trace elements that your specific crop requires for optimal growth and yield. Just like in soil-grown plants, a tell-tale sign that your plants aren’t getting the right amount, or type, of nutrients is a sick looking plant e.g. yellowing leaves.
For both horizontal and vertical hydroponic systems, it’s important to ensure that the nutrient solution reaches all of the plants. If you're working with crops like lettuce, herbs, or other leafy greens, a basic hydroponic growing kit will provide all the tools you need to manage nutrients efficiently.
Methods of Growing Hydroponically
Ebb and Flow Tables
The Ebb and Flow system temporarily floods the plant roots with nutrient solution before draining it back into the reservoir. This cycle repeats at set intervals, providing oxygen-rich periods followed by nutrient absorption. It’s ideal for plants that need varying levels of water and nutrients throughout the day, like peppers or herbs. This system is easy to automate, though it requires careful monitoring or moisture sensors to avoid overwatering.
Nutrient Film Technique (NFT)
In the Nutrient Film Technique (NFT), a thin layer of nutrient-rich water is continuously circulated over the plant roots inside a shallow channel. This method is ideal for lightweight crops like leafy greens and herbs because it provides easy access to both nutrients and oxygen. The shallow water flow ensures that plants are never waterlogged, promoting faster and healthier growth. It’s a popular choice for small spaces and commercial setups due to its simplicity and efficient use of water.
Wick System
The Wick System is one of the simplest hydroponic methods. A wick draws nutrient solution from a reservoir to the plant’s roots. This passive system doesn’t require electricity or pumps, making it ideal for beginners or those growing small plants like herbs or leafy greens. However, it’s less suitable for larger plants that require more water and nutrients.
Deep Water Culture (DWC)
Deep Water Culture (DWC) involves suspending plant roots directly in a nutrient solution. An air pump delivers oxygen to the water, preventing root rot and ensuring plants get the oxygen they need. This method is great for fast-growing plants like lettuce and some herbs. The constant access to nutrients makes DWC highly efficient, though it requires more monitoring to ensure oxygen levels and nutrient balance are maintained.
Hydroponic Vertical Towers
Hydroponic vertical towers, such as our GROW Towers, are an innovative method that maximises growing space by using vertical columns to stack plants. This system is ideal for polytunnels and greenhouses where space is limited, allowing you to grow a large number of plants in a small footprint. Water and nutrient solutions are pumped to the top of the tower and trickle down through the roots of each plant in the column, providing an even distribution of nutrients. Vertical towers are perfect for crops like leafy greens, herbs, and strawberries, as they thrive in vertical arrangements.
This method is highly efficient because it uses vertical space rather than horizontal, making it possible to grow up to 42 plants per square metre. For growers looking to maximise productivity, especially in smaller or confined spaces like polytunnels, vertical hydroponic towers offer an ideal solution for increasing yield while maintaining efficient use of resources.
Choosing the Right Growing Media
Because crops grown hydroponically aren’t reliant on soil to deliver their nutrients, it’s important that you are utilising the best growing medium for your crops, in order to maintain stability and moisture, as well as avoiding root rot. It’s important to note, that there is no ‘best’ type of growing media – the medium you choose should be suited to the crop you’re growing, the micro-climate you’re in and the hydroponic system you’ve chosen.
Some of the most popular options include:
Rockwool: A great option for vertical hydroponic towers because it retains water and nutrients well, providing a stable environment for quick-growing leafy greens. It also has a good air-to-water ratio, providing aeration to roots and preventing from becoming too wet, and rotting, which is ideal for quick growing leafy greens such as lettuce, kale and spinach.
Coconut Coir: If you’re growing a variety of crops in your hydroponic system or tower, coconut coir can be a great option. Coir GROW bags are an eco-friendly alternative to peat and are perfect for holding moisture and nutrients. Coconut coir retains water effectively without becoming waterlogged, making it perfect for Asian greens that need constant moisture.
Clay Pellets: Often used in hydroponic growing pots, clay pellets are lightweight, reusable, and provide excellent drainage, which is essential for avoiding waterlogged roots in vertical systems. The Dutch Bucket system, which incorporates clay pellets, is very popular with some growers. The pellet's porous nature ensures a great oxygen-to-water balance for your hydroponic crops. Strawberries in particular benefit from the great drainage and aeration that clay pellets offer in a hydroponic setup.
Perlite: Perlite is made from volcanic glass. Due to its lightweight and porous composition, perlite offers excellent drainage, aeration, and moisture retention for hydroponic systems. You can use perlite on its own, or mix it with other growing media. Crops such as tomatoes, peppers and herbs do well when grown hydroponically with a perlite mix.
Choosing the right media will help ensure that your plants get enough oxygen and nutrients while growing hydroponically in your polytunnel.
Maximising Space with Vertical Hydroponic Towers
Vertical hydroponic farming solutions are not only space-saving, but increase yield per square metre of your polytunnel. By utilising the height of your polytunnel, you are able to make use of the vertical space, growing plants somewhat on top of one another, increasing your available growing area. Vertical hydroponic towers are particularly effective in smaller polytunnels, because they let you grow a range of crops, from leafy greens to strawberries, without taking up valuable ground space. On a commercial scale, vertical hydroponic farming is an efficient solution in order to maximise yields.
What to grow in your vertical hydroponic tower:
Vertical farming is especially suited to growing vegetables and herbs, though some fruits also thrive in these systems. Here are some of the best crops for your vertical setup:
Leafy Greens: Lettuce, spinach, and bok choy thrive in vertical hydroponic gardens and can be grown in towers or vertical planters.
Herbs: Basil, parsley, mint, and cilantro do well in hydroponic grow gardens, especially when grown vertically in small spaces.
Strawberries: These fruits are well-suited for vertical gardens because they need less root space and can benefit from the upward growth offered by vertical systems.
Tomatoes and Capsicum: Although these both require more space, using hydroponic vertical growing methods can still provide excellent yields inside a polytunnel.
Optimising Your Hydroponic System for Maximum Yield
To optimise your polytunnel’s hydroponic system for maximum yield, careful monitoring and adjustment of nutrients are essential. Regularly check the pH and nutrient levels in your system to ensure plants can absorb the right nutrients efficiently. A pH range of 5.5 to 6.5 is ideal for most plants, and using a quality nutrient solution tailored to your crops will boost growth. Additionally, maintaining proper airflow and temperature inside your polytunnel is crucial for plant health. The use of fans, shade nets and vents can help control humidity and prevent stagnant air, while keeping temperatures lower to create an environment where your plants can thrive without the risk of overheating or dampness. This balance will ensure both healthy plant growth and increased yields.
Growing hydroponically inside a polytunnel, particularly when coupled with vertical growing methods, is a game-changer for those looking to grow more food in less space, reduce water usage, and achieve higher yields year-round. Whether you’re a commercial farmer or a backyard grower, hydroponic farming offers a solution to the challenges posed by traditional agriculture, especially here in Australia where water conservation and space efficiency are essential.
By investing in hydroponic growing infrastructure, mastering hydroponic growing methods, and utilising vertical garden ideas, you can transform your growing operation and enjoy the many benefits of hydroponic farming.
Explore the possibilities of growing hydroponically in a polytunnel with our Australian-owned polytunnel kits, and embrace the future of farming today.
