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 hy­dro­, 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.

The Dutch bucket sys­tem works on the same prin­ci­ple as an NFT, but the plants are kept in big­ger con­tain­ers to al­low their roots more room, which means you can grow larger types of crops.

The­u­nis and Marie Naudé were able to move their nu­tri­ent film tech­nique (NFT) sys­tem from their flat to their new town­house. They are reap­ing the re­wards, like the juicy cherry toma­toes above.

Tony and Me­gan Hinde, the head and heart be­hind hy­dro­ Me­gan, who runs the on­line shop and two branches in Cape Town, says she grew up with a hy­dro­pon­ics tun­nel in the back gar­den. Be­fore her fa­ther re­tired, he used to sell veg­eta­bles such...

Plants are an­chored in bas­kets and their root sys­tems grow through open­ings in the bas­kets to hang in the wa­ter. If you re­move a plant from the wa­ter, it’s clear how the roots start grow­ing al­most overnight.

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