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Greenhouses or glasshouses?
'Greenhouse horticulture' also known as 'protected cultivation', 'protected cropping' and 'covered cropping' means growing crops in glasshouses or greenhouses. Greenhouses can be covered with glass or plastic, such as single or double poly-ethylene, synthetic sheets, etc., while glasshouses are obviously covered with glass.
Why using a greenhouse/glasshouse?
Greenhouses are used world-wide to protect crops from adverse external conditions (cold, wind, rain, snow, hail, excessive radiation, heat, etc). On top of that, greenhouses/glasshouses allow control of the growing conditions, which enables steering plant growth, production, quality and timing. Timing of harvest is paramount for instance in flowers that are produced for certain festivities. Typical aspects of greenhouse cultivation are growing conditions (climate), energy input, crop cultivation, hydroponics, irrigation, fertigation, plant nutrition, water treatment, pest & diseases, IPM (integrated pest management), crop recording. A computer and specialised software are essential for proper control.
Greenhouse crops
Traditional greenhouse crops are tomatoes, peppers (capsicums), cucumbers, eggplant (aubergine), lettuces, roses, carnations, gerbera, lilies, potplants, garden plants and many other ornamental crops. Less traditional are herbs, medicinal and other beneficial crops, fodder for animals, and more.
Growing conditions
Plants respond very strongly to the growing conditions: light, temperature, humidity, CO2 concentration, as well as root-zone conditions. The grower can manipulate the growing conditions to steer plant growth, production, quality and timing quite precisely. Click here for more info on growing conditions.
Greenhouse control & Energy
Greenhouses usually have facilities for heating, venting (cooling), irrigation, and often much more, such as CO2 enrichment, fogging/misting, screening, lighting, day length control, etc. Heating and CO2 enrichment require quite a lot of energy. Given the high costs of fuel, energy efficiency has become very important. Energy consumption depends largely on how the greenhouse conditions are controlled. In addition, a wide range of energy saving devices and measures can be applied. Click here for more info on greenhouse control and energy efficiency.
Hydroponics & Nutrition
Typically the crops in modern greenhouses are grown 'soil-less' (out of the soil): plants are grown in a substrate or in nutrient solution ('hydroponics'), or even in wet air ('aeroponics'). Soilless systems allow better control of plant health (preventing and controlling root diseases) and better control of the growing conditions in the root-zone: temperature, airation, acidity (pH), nutrients (EC or CF). A soilless system can be in an open system ('run-to-waste system') or a closed system ('recirculating system'). Substrates contain no or little plant nutrients, so these need to be supplied by so-called ‘fertigation’ (fertilisation + irrigation). Therefore a nutrient solution is supplied containing the essential nutrients. Click here for more info on Hydroponics & Nutrition.
Water treatment
Plants use an enormous amount of water for transpiration and a small amount for growth. Abundant and good quality water is essential for achieving top quality growth and production. Characteristics of water are its chemical composition (does it contain salts, iron, calcium?) and its micro-biological quality (is it free of bacteria, algae, diseases?). There are many water treatments available, and it just depends on what sort of problem needs to be solved. More on water treatment can be found here.
