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Hydroponics and undercover growing


Translated directly, hydroponics means plants working (growing) in water. The word hydroponic is derived from two Greek words: hydro – meaning water, and ponos – meaning labour.

A modern definition of hydroponics: A system where plants are grown in a growing media or substrate other than natural soil. All the nutrients (6 macro- and 6 micro-elements) are dissolved in the irrigation water and are supplied at a regular basis to plants. It is the cultivation of plants in nutrient-rich solution rather than in soil.

Hydroponics supplies the plant with what it needs, when it needs it. There is no genetic mutation that takes place inside the equipment nor are any mysterious wonder chemicals introduced to the plant roots.

In hydroponics, water is used much more efficiently than in soil cultivation. In certain hydroponic closed systems (recirculation) probably as much as 50% less water is used, while in open systems (drain to waste) 20-30% water savings can be realised. Hydroponics can be incredibly sophisticated and requires good management.

Hydroponics gives better and faster plant growth and potentially greater yields since the growth factors such as nutrients, temperature, humidity and light are closer to the plant’s exact needs. In some hydroponic environments you can grow the plants much more closely together than with conventional methods (provided there is sufficient light). This is because the plants do not make as large a root system as under conventional conditions since they don’t have to “go looking” for food. The food “comes” to them.

In South Africa, hydroponic vegetable production is almost always done under protection (e.g. tunnels covered in special plastic and shade-cloth).

Although “Undercover” is mostly seen as greenhouse and tunnel production, shade-cloth systems (where plants are grown mainly in soil but protected from harsh climate by the shade cloth) is also included in this category.

The difference between hydroponics vegetable production and production in soil:

HydroponicsField production
No soil is required.Good topsoil is required. Good soil = good drainage, texture, organic material (e.g.compost), disease-free.
Nutrients are available at all times. Only water-soluble fertilisers are used. Hydroponics fertiliser formulations contain a balanced nutrient content, taking the plant species and growth stage, climate and water conditions into consideration. Nutrients must be added to soil. Unless a laboratory analysis is done, too much or too few nutrients can be added.
A great advantage with greenhouses is that since you can grow vegetables out of season when the prices are good.Vegetables can only be grown in season.
Soil borne diseases can be controlled.Soil borne diseases can build up in the soil.
Hydroponic production is not organic because artificial nutrients are always used and plants are never grown in soil.It is possible to produce organic vegetables in soil because one can use organic fertilisers such as compost and manure.


Advantages/disadvantages of Hydroponics vegetable production

  • Hydroponically produced vegetables can be of high quality and need little washing.
  • Hydroponically produced crops tend to have a higher grade than conventionally produced crops in the open field.
  • Soil preparation and weeding is reduced or eliminated.
  • It is possible to produce very high yields of vegetables on a small area because an environment optimal for plant growth is created. All the nutrients and water that the plants need are available at all times.
  • Good soil is not a prerequisite to grow vegetables.
  • Water is used efficiently.
  • Pollution of soil with unused nutrients is greatly reduced.
  • Hydroponics production is management, capital and labour intensive.
  • A high level of expertise is required.
  • Daily attention is necessary.
  • Specially formulated, soluble nutrients must always be used.
  • If not monitored and controlled carefully, disease and insect populations can increase dramatically to cause great losses.
Source: Johannes Maree.

Whereas hydroponics uses a liquid nutrient solution as a growing medium and aquaponics (see separate page) uses water and fish waste, aeroponics uses no growing medium at all. Plants are grown in the air or in mist. However, since nutrients are given to the plants through water, aeroponics can be considered  a type of hydroponics.

Closed and Open Systems

Many different hydroponic or soilless culture systems are in use today. In true hydroponics no medium is used, which is typically called liquid hydroponics compared to aggregate hydroponics in which a soilless medium is used. These mediums can be organic (sawdust, wood-shavings, wood chips, coco-peat, etc.) or inorganic materials (gravel, perlite, rockwool, vermiculite, etc).

Both liquid and aggregate hydroponics can be used in an open or closed production setup. In a closed system the excess nutrient solution (runoff) is recovered and reused. While in an open system the runoff is channelled away and not reused in the system. It is important to mention that in a closed system the reservoir is normally flushed once a week and a completely new batch of nutrient-rich water made up.

Advantages and disadvantages

Open SystemClosed System
1. Initial capital outlay is less.1. Initial capital outlay is more because it needs more pipes, pumps, a water purification system and bigger reservoir.
2. Use more water.2. Use less water.
 3. Use more fertiliser.3. Use less fertiliser.
4. Less change of contaminated nutrient rich solution.4. Greater change of contamination of nutrient rich solution.
5. Less expense and capitalisation needed to sterilise nutrient rich solution.5. Greater expense and capitalisation needed to keep recycled nutrient rich solution sterile.
6. Greater negative impact on environment.6. Less negative impact on environment.

In South Africa two types of hydroponic systems are most often used.

  1. The most common system is the open bag culture system (or drain-to-waste system). In this production type, tomatoes, cucumbers and sweet peppers are produced in tunnels or multi-spam structures and grown in plastic bags or containers filled with media such as pine sawdust or Coco-peat.
  2. The second system is the closed gravel flow technique systema closed, gravel flow technique system (GFT). In GFT, vegetables such as lettuce and celery are produced in troughs filled with gravel, normally under shade-cloth.
Source: Johannes Maree

For the newcomer

What do I need to start a hydroponics production unit?

Garden units

  • source of clean water
  • the right location
  • specially formulated fertiliser
  • time to attend to the system daily
  • a little knowledge of plants and gardening
  • a commercial or home made unit


  • Water is the most important consideration – quality, quantity and reliability.
  • A market. Know what, where and when to market your crop.
  • Hydroponics is labour intensive. During peak season, labour must be available for 7 days a week.
  • Management skills: production, labour, marketing, infra-structure
  • Expertise in crop production, fertilisation and irrigation, pests and disease management
  • Location: infrastructure, labour, market, etc.
  • Financing: the amount needed depends on the size, type of greenhouse, labour cost and your market.
  • Dedication


Know the basics

To be able to produce vegetables successfully year after year, one needs to be familiar with the basics of hydroponics that is: the plant, growth medium, water and nutrients. By relying on recipes only, one will not be able to identify the cause of a problem and you may not be able to correct them.


How do plants function?

Plants have only three types of organs: leaves, roots and stems. Know what the organs look like and how they function so that you can deal with their needs.


Growth medium

Growth medium is the substitute for soil in hydroponics systems. The functions of growth medium are:

  • to provide the roots with O2
  • bring the water and dissolved nutrients in contact with roots
  • anchor the plants so that they do not fall over

Many different materials can be used as long as they provide the roots with O2, water and nutrients.

In South Africa, gravel is popular in re-circulating systems, sawdust is the most popular for the open bag system / drain to waste system.


Water and nutrients

All the nutrients plants need are dissolved in water and they are supplied to plants every day. Macro elements (N; P; K; S; Ca) are needed in substantial amounts, whereas plants need very small amounts of micro elements (Fe; Zn; Mn; Mg; Cu; Co, Mg).

It is necessary to use specially formulated fertilisers. Fertilisers used for hydroponics are more pure (and expensive) than other fertilisers to prevent precipitation and blockages of the system.


Different hydroponics systems

Two different hydroponics systems are used to produce vegetables: the gravel flow and the drain to waste system.

  • In the drain to waste system, plants are grown in containers and nutrient solution is supplied to plants by means of a dripper, up to 12 times per day. The number of irrigation cycles per day depends on temperature and the growth stage of plants. The crops in the drain to waste system grow tall and need to be trained and pruned so that they grow upwards as a single stem.
  • In the gravel flow system, the nutrient solution is re-circulated and the roots of the plants stand in a thin film of nutrient solution all the time. Gravel or sand is used most often as growth medium.


Which crops can be grown in a hydroponics system?

Any crop can be grown, but some will not be cost effective e.g. cabbages. Presently, what is popular in South Africa are tomatoes, cucumbers and peppers in a bag culture method with an open system drain to waste systems and lettuce and herbs in gravel flow systems.


Which crop should I grow?

Nobody can make the decision of which crop to grow for you. Every situation, every crop and every market has its own advantages, disadvantages and requirements. Important considerations are the market and the climate. The type of unit e.g. garden unit or commercial unit is also a factor in determining which crops to grow.


Which variety do I choose?

There are many vegetable varieties available. Some were developed specifically for commercial hydroponics production in greenhouses. Local seed companies are able to recommend varieties that are widely adapted and easy to grow. For household units common garden varieties are recommended.



  • Seedlings can be purchased at nurseries, or you can produce them yourself.
  • When buying seedlings, look for young plants; the roots must not be stuck to the walls of the seedling tray and must be white, not brown.
  • Soil- and water-borne diseases can be transmitted through seedlings.
  • Transplant only the strongest seedlings.
  • Do not use seedlings that are too old and ‘pot bound’.

To produce seedlings, follow instructions on seed packages.


 Buying seed

  • Seed is available in small or large packages.
  • Small packets are sold at nurseries, co-ops and retail stores and are suitable for garden and small-scale hydroponics units.
  • Large packets, suitable for commercial scale production, are available from seed companies.


Taking care of plants

  • Different crops are planted at different spacing. Small plants can be planted close to each other. Large plants need more space to grow and must be spaced further apart.
  • Water flow must be checked every day and adjusted when necessary.
  • If plants turn yellow, it is normally a symptom of nutrient deficiency, too little light or a disease.
  • Inspect the leaves every day for disease symptoms and insects. Act immediately if a problem occurs.



Vegetables are perishable. The shelf life and quality depend on a chain of actions:

  • Pick at the right stage without damage to the plant.
  • Pick early in the morning or when it is cool.
  • Keep picked vegetables out of the sun.
  • Handle carefully. Store them at the right temperature (depends on crop).
  • Use the right packaging (depends on crop and market).
  • Transport with care.
Source: Johannes Maree

Local business environment

Hydroponics has become a very important way to produce vegetables in South Africa because of the production potential, the high quality of the produce and the efficient water usage. Production of flowers or vegetables, especially for the export market, is unthinkable without undercover growing. If produced in a climate-controlled greenhouse, the producer can supply vegetables out of season when the price is good.

  • Commercial scale hydroponics production is capitallabour and management intensive.
  • Flowers offer by far the best opportunities for environmentally controlled farming, with roses, mini roses, chrysanthemums, carnations, gysophili, gerberas, asters, alstromeria, cymbidium and ferns all easily saleable between October and mid-April in the Far East. Prices for cut flowers such as mini roses and alstromeria are substantially higher in this period when Northern Hemisphere production is limited because of dull skies and the high cost of heating. Markets also exist for a range of vegetables, including peppers, courgettes and cherry tomatoes, but profits may be lower. In South Africa plants are grown in greenhouses to protect them against the strong UV radiation, to increase the humidity around plants, and to decrease to some extent the extreme minimum and maximum temperatures that can occur in a single day.
  • The principal advantage of plastic tunnels is that they are significantly less expensive, but they do not offer climate control. Tunnels are often not warranted against high winds. Planting space in tunnels is less favourable than in greenhouses and the installation of climate control is very expensive and therefore not recommended for tunnels.
  • The permanency and rigidity of an atmospheric controlled glasshouse provides excellent protection against temperature fluctuations and strong winds. A well constructed and erected greenhouse, with proper insect preventing netting, will drastically reduce the incidence of insects (making this pest more controllable). If the temperature and humidity are very high and ventilation and circulation is poor, incidence of diseases may occur though.
  • Pricing: Controlled environment farming is not cheap to introduce. Half a hectare would generally be the minimum viable size for cut-flower only enterprises. Lack of finance has restricted the SA greenhouse industry, but there are sources other than local banks for farmers to get credit. There are a number of companies that assesses the suitability of developing world farming ventures for funding from European financiers. European financiers require projects that are practically and economically viable, run by people with the necessary technical and managerial expertise and that have guaranteed markets for their produce. Growers should have done some extensive planning before they consider contacting these companies. Potential growers must prepare a feasibility study, including a marketing plan, the project’s running costs and projected cash flow for its first year and subsequent five-year period – markets must also be already identified.
Source: Johannes Maree

Despite the high upfront costs, hydroponics projects can provide good returns to investors if carefully planned and implemented.


It is important to ensure that the business is large enough to justify the overhead costs and the level of managerial and logistical support required (economies of scale). In this regard a project linked to an existing business will invariably be more profitable than a standalone project.


Source: Stephen Hobson, Agrifusion

Role players

Note: Click to expand the headings below. To get a free listing on our website like the ones below, visit here for more information or place your order hereDisclaimer: The role player listings are not vetted by this website.

Filmflex Plastics – “Home to everything Hydroponic & Crop Care”
Dube Tradeport – Find the “Agriculture” option on the website. A plant tissue culture facility, nurseries and “the largest climate-controlled glass-covered growing area in Africa” are included in the offerings here.
Horti Shop – Hydropnic and aquaponic systems and components

Further reference:


  • Provincial Departments of Agriculture and their linked Colleges of Agriculture are involved with hydroponics and covered growing research and training.

Training and research

Websites and publications

Visit the websites listed earlier on this page.

  • Companies involved supply technical publications on subjects relating to vegetable production. Some of these notes appear on their websites.
  • The DVD “Successful hydroponics production is available from Kejafa. Visit
  • Dicla Training Centre sells the DVD “Hydroponic Production in Tunnels”. See
  • Undercover Farming, a bi-monthly magazine, is for greenhouse, tunnel, shade net and hydroponics farmers. Find more at
  • Call 012 842 4017 or email iaeinfo [at] for the following publications available from ARC-Agricultural Engineering: (i) Low-cost shade net structure (ii) Development of an automatic rolldown shade-net for glasshouse compartments
  • The AgriSETA Assessment Guide Primary Agriculture “Monitor the establishment of a crop” includes tunnel crops.
  • Find the Aquaponic and Hydroponic farming in Africa FaceBook page at
  • Niederwieser, J.G. & CP du Plooy, C.P. (Eds). 2014. Guide to Hydroponic Vegetable Production. Pretoria: Agricultural Research Council, Roodeplaat Vegetable and Ornamental Plant Institute. Order it from ARC-VOP at 012 808 8000.
  • Niederwieser, J.G. (Ed.) 2001. Guide to Hydroponics Vegetable Production. Pretoria: Agricultural Research Council, Roodeplaat Vegetable and Ornamental Plant Institute. ISBN: 1-86849-196-X.
  • Harris, D. 1992. Hydroponics: The Complete Guide to Gardening Without Soil. Cape Town: New Holland.
  • Find the Production guidelines: hydroponic vegetable production on (look under “Resource Centre” on the “Old website” options).



  • The global indoor farming market size was valued at USD 38.7 billion in 2022 and is expected to expand at a compound annual growth rate (CAGR) of 9.6% from 2022 to 2032, totalling around USD 96.6 billion (Future Market Insights, 2022).
  • Find the Global Indoor Farming Companies: The Top 300 Report (2023) at
  • Food and Agriculture Organization of the United Nations. 2017. “Good Agricultural Practices for greenhouse vegetable production in the South East European countries: Principles for sustainable intensification of smallholder farms”. FAO PLANT PRODUCTION AND PROTECTION PAPER. Available at
  • For global greenhouse news –


Some articles

Sources for the technical information on this page: Johannes Maree and Petrus Langenhoven.

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