DIY
Build a hydroponic wall garden
The term hydroponics sounds like a somewhat futuristic concept: plants are grown in water, with white roots that never see soil but grow flat-out.
Those in the know say it is futuristic – it is the future of food production. “With the rapid growth of the world’s population, it’s the only way we’ll be able to feed everyone,” predicts Wynand Bezuidenhout, owner of Grow Machines, a business near Standerton, Mpumalanga, that builds hydroponic systems for commercial and hobby farmers. Wynand says hydroponics is especially popular in the US, Israel and the Netherlands, where it’s used for commercial food production. South Africa is not far behind these countries with this technology, he says. Several local farmers are already using hydroponics to grow lettuce and herbs, whereas the tulips you buy in Woolworths probably come from Adriaan van Wyk’s farm near Rawsonville – he cultivates up to
140 000 stems a week on a patch of land spanning only 1 600m².
“When you buy salad and see it’s totally clean or still has white roots without any soil on it, you know it’s probably a hydroponic product,” says Elaine Hinde, co-owner of the online hydroponics shop hydroponic.co.za, a site managed by the Hinde family.
Elaine’s daughter Megan, who runs their two Cape Town shops, says their customer base has grown over the past two years, especially with the strict water restrictions imposed in this region. “We’ve been inundated with questions, so we’ve added an introduction to the basic principles of hydroponics on our website for novices.”
The Hindes say it’s vegetable-garden enthusiasts in particular who are getting excited about hydroponics.
What is hydroponics?
Also known as hydroculture, this is the practice of growing plants in water rather than in soil. Nutrients are added to the water as the plants need them.
The drought in many parts of South Africa – in the Western Cape the most severe one in more than a century – has played a major role in the popularity of hydroponics as a hobby.
“It’s an excellent solution for a country with water scarcity, because it’s much more water-wise,” says Wynand. “It’s a closed system, and no water is lost the way it would be in an ordinary vegetable garden >
There are numerous other benefits: better, faster harvests; better quality plants; and fewer pesticides. “The plants grow better and faster because you create the optimal root conditions,” says Wynand. “They have enough water, nutrients and oxygen, which means they don’t waste energy searching for them and can push all their energy into the growth process. Water also provides less resistance to the plant roots than soil, allowing the plant to grow even faster. Because there is always enough water, the plants never wilt, further accelerating the growth process.”
Moreover, as any organic gardener will tell you, strong plants are less susceptible to pests. “Hydroponics eliminates soil pests like cutworm,” says Megan. Especially with home systems, says Wynand, you need little or no pesticides because the plants are strong enough to resist pests.
Another advantage of hydroponics is that you don’t need a lot of space. Theunis Naudé from Stellenridge in Cape Town can attest to this. He built a system on the balcony of his flat for himself and his wife, Marie. “We lived on the first floor of an apartment block, with an enclosed balcony where we had a small herb garden in pots, but the herbs always died. So when I heard about hydroponics, I was excited,” says Theunis. It took him about a day to build a system with 12 plant holes; it cost him R1 000.
He says it was clear right away that this new system worked better than the herb garden they had before. “It uses less water, the plants are healthier, and it takes up no more space than the few pots of herbs we had.”
When they moved to a townhouse, Theunis took the whole system along. At the moment it is full of cherry tomatoes. He says that with their nutrient film technique system (see “Choose your system” below) they harvest enough for a salad at least twice a week – about five cherry tomatoes per day. He’s planning a Dutch bucket system, which will enable him to grow plants with a larger root system. “Then I’ll be able to plant climbing tomatoes without the need to fuss with the roots. At the moment, I prune the root mat in the pipe regularly to make sure the plants get enough water and oxygen, and to stop the roots from blocking the pipe.”
With hydroponics, you can scale your garden up or down as you like by simply adding or removing a pipe.
Choose your system
“You can make hydroponics as easy or complicated as you like,” says Tony Hinde. He explains the three most common hydroponics systems briefly: Nutrient film technique (NFT) This involves anchoring plants in a basket filled with a growing medium such as perlite, coir or Leca (a material made of heated clay). These substances only serve as an anchor for the plant and have no nutritional value. The basket fits neatly in a gutter or pipe that allows a smooth flow of shallow water
“The plants grow better and faster because you create the optimal root conditions. They have enough water, nutrients and oxygen, which means they don’t waste energy searching for them.”
to circulate continuously – the roots of the plants hang in the water and form a thick mat. The upper part of the root mat is above water, so it is exposed to air (but not light). This way the plants get enough nutrients and oxygen. The water is supplemented with nutrients that are suitable for the kind of plants you cultivate – leafy vegetables like lettuce, kale and spinach need a specific level of nutrients, whereas plants bearing fruit, such as tomatoes, eggplant and gem squash, require another level. A pump in a container of water ensures a steady flow through the gutter at all times. This system works especially well for leafy vegetables and herbs. (See the Naudés’ system opposite.)
Dutch bucket system This system (below) is similar to NFT, but the plants are grown in buckets full of water and growing medium rather than in a shallow stream. The buckets are connected to one another by way of pipes and a pump, and the water flows through all the buckets. This system works well for plants with a larger root system, needing more space to grow. Flood-and-drain system Also called ebb and flow, this option operates on the same principle as sea tides. Plants are anchored in a watertight container using a medium such as river sand or gravel, and the container is pumped full of water once or twice a day. The water drains back to the pump slowly until it’s time to pump the container full of water again. The system works well if you have space and want to plant more crops – it looks almost like an ordinary vegetable garden, especially if you hide the pipes and pumps. (See Ken Bond’s garden on page 103.)
Looking after the water
Temperature Megan says the best water temperature for hydroponic plants ranges from 18ºC to 22ºC. If the temperature is too high or too low, you run the risk of root rot as a result of too little oxygen and/or a pythium infection. The best way to regulate the temperature is to choose a spot in your garden that is moderate – possibly in shade for half the day or one that gets a breeze if you live somewhere really hot. Other solutions? Use shade cloth to keep the water cool (see right) or bury the water tank. You can also wrap a length of fabric or another insulator around the container to limit variance in temperature. In high summer, water consumption will be higher Check the container and gutter – as long as there’s always a smooth flow and the pump is under water, there is enough water. The high water consumption also affects the nutrition, so keep an eye on the plants for signs of too many (leaves that seem burnt) or too few nutrients (leaves that are often yellow). The nutritional ratio is called the electrical conductivity level (EC).
pH The ideal pH level for water in a hydroponic system is between 5,5 and 7. A pH meter is affordable and easy to use, and therefore worthwhile.
Use the correct shade cloth A hydroponic system won’t necessarily require shade cloth, but if is in full sun or in a position where it gets hot, shade will help with water consumption and temperature. Choose a shade percentage of 20 (only in black and white, not green) to make sure the right kind of light is filtered.
Keep a record The Hindes recommend recording pH levels, replacement of nutrients, weather and light conditions, when plants are planted, when water is replaced, and so forth. This makes it easier for you to spot a pattern and learn faster what works and what doesn’t. >
What are the best plants for hydroponics?
Megan says the easiest plants to grow are leafy vegetables such as spinach, kale, lettuce and herbs, especially basil. As far as fruit-bearing plants are concerned, try tomatoes, strawberries, eggplant and various types of pumpkins and marrows – but make sure you allow ample room for the roots and climbing.
“You can grow 99% of vegetables successfully in a hydroponic system, as long as there is enough space,” says Wynand. He even started experimenting with tuber crops such as potatoes. “Our first potatoes have already been harvested, and they are looking good!”
The right nutrition
Add nutrients according to the seedlings you buy: leafy vegetables take one concentration, whereas fruit-bearing plants such as tomatoes require a higher concentration when they begin to bear flowers and fruit. Your hydroponics provider will be able to advise you about which nutrients to apply and when.
Watch out for these pitfalls!
A system full of algae This happens when water is exposed to sunlight and/ or the water is too hot. Paint the pipes and gutters to protect them from the sun, use shade cloth, and make sure everything is covered properly.
Rotten plants or roots Insufficient oxygen is probably the cause. Make sure the water level is not too high. It may also be that oxygen levels are low because of the presence of algae. Clean the system well every few months. Keep the water temperature at optimal levels, and add a fungicide if phytium is a problem. Adding an air stone is cost-effective and will improve oxygen levels if all else fails. No electricity! The one major disadvantage of an NFT hydroponic system (such as the step-by-step DIY project on page 105) is that it runs on electricity. If that goes off while you’re away from home, you may be able to save the plants if you discover it in time. Some farmers use solar panels, which aren’t cheap, or a generator. Ken Bond’s flood-and-drain system (opposite) overcomes the problem to some extent – the pump is only switched on for five minutes once a day.