Protected Plant Production - BHT223

Learn to Grow Crops in a Greenhouse.

  • Extend crop production throughout the year.
  • For vegetable, cut flower or herb farming


This course consists of 10 Lessons:

  1. Structures For Protected Cropping
  2. Environmental Control
  3. Cladding Materials And Their Properties
  4. Irrigation
  5. Nursery Nutrition
  6. Relationship Between Production Techniques And Horticultural Practices
  7. Horticultural Management In A Greenhouse: Pests And Diseases
  8. Harvest & Post Harvest Technology
  9. Greenhouse Plants
  10. Risk Assessment

Course Aim   

Successful completion of this course/module will develop your broad understanding of practices and processes involved in successful protective plant cropping.

It will develop a clear understanding of environmental control and plant growth within a protective environment, together with a practical knowledge of plant husbandry techniques.


  • Describe and Evaluate the type and shape of modern growing structures
  • To describe and evaluate environmental controls in protected cropping
  • To explain the nature of solar radiation, transmission properties of glass and its substitutes
  • Determine the water requirements of a crop; and methods of irrigation.
  • Relate horticultural principles to the production and harvesting of a range of crops.
  • Evaluate the factors involved in marketing protected crops
  • Evaluate the factors involved in marketing protected crops
  • Undertake risk assessment

This course involves both practical and theoretical tasks which involve you doing a wide variety of things, including:

  • Identify the main types of growing structure
  • Relate use of structures to shape and type of construction
  • Identify the range of environmental factors controlled within a growing structure
  • Describe the use of the equipment used to measure and monitor these factors
  • Name and describe a range of types of environmental controls
  • Evaluate the use of IT facilities for environmental control
  • Describe the meaning of “daylight” and explain the role of sunlight and diffused light
  • Relate time of year to the quantity and quality of available light
  • Evaluate how the shape and orientation of a structure will affect light transmission
  • Assess the effectiveness of glass and cladding alternatives for light transmission
  • Describe the durability and insulation properties of glass and alternative materials
  • Select and describe appropriate systems of irrigation for plants grown in situ
  • Select and describe appropriate systems of irrigation for container grown plants
  • Specify and evaluate systems for incorporating plant nutrients into the irrigation water
  • Explain the effects of environmental control on a range of plants
  • Relate the essential features necessary for successful plant establishment and development to their underlying scientific principles.
  • Describe the production of a range of crops
  • State the optimum stage of growth for harvesting a range of crops
  • Describe the harvesting systems for protected crops
  • Explain how shelf life can be affected by treatment of the crop before and after harvest
  • State the factors to be considered when marketing crops
  • Evaluate alternative marketing outlets
  • Relate packaging and presentation to marketing
  • Assess benefits to the grower and customer, of grading a crop before marketing
  • Determine elements of risk in the practical operations associated with protected plant production.
  • Identify safe working practices

Duration - 100 hours



Growing in a greenhouse opens up a lot of possibilities for controlling aspects of the crop production; but it can also create an unnatural environment that may have detrimental aspects unless you exercise control properly over the environment.

  • Greenhouse temperatures may not always be optimum for plant growth. They may rise too high or drop too low.
  • Levels of carbon dioxide, oxygen and other gases in the air can become inappropriate for a plant
  • In a sealed off environment humidity can rise beyond what is ideal for crop growth.
  • Light levels may be diminished, or magnified in some greenhouses.

All of these factors are manageable; but managing them requires knowledge and experience.

Relative Humidity and Vapour Pressure Deficit

The amount of moisture held in the air of the growing environment has major effects on many aspects of crop development and disease prevention.  Relative humidity (RH) levels are a measure of the amount of moisture currently held in the greenhouse air and are influenced by factors such as the amount of water vapour given off by the plants during transpiration, any misting, fogging or damping down used for temperature control as well as ambient humidity levels in the air brought into the growing area.  High RH slows the rate of water loss via transpiration from the plants, thus slowing the transport of water and calcium from the roots to developing plant parts.  High humidity also increases the risk of fungal and bacterial pathogen infection, particularly where condensation may wet foliage.  Low RH increases the rate of transpiration and foliage desiccation can occur, plants may also wilt during the warmest part of the day.    

Greenhouse sensors often measure both RH and the Vapour pressure deficient (VPD) which is more meaningful from a plant growth perspective than RH.  VPD is the difference between the amount of moisture in the air and how much moisture the air can hold when saturated.  VPD is better than just looking at RH as it takes into account the effect of temperature on the water holding capacity of the air, rather than giving just a relative measure of the water content of the air.  VPD gives an absolute measure of how much more water the air can hold, and how close it is to saturation.  Higher VPD values means that the air has a higher capacity to hold more water and this stimulates plant transpiration from the leaves.  Lower VPD means the air is at or near saturation, so the air cannot take more moisture from the leaf in this high humidity condition.  Higher VPD increases the transpiration demand and assists with prevention of conditions such as blossom end rot, fruit cracking and tip burn.  VPD in crops such as tomatoes are best run below 0.062 psi (0.43 kPa) for good plant growth, however disease infection is most damaging below 0.030 psi, so greenhouse climates are best adjusted to keep above 0.030 to prevent disease outbreaks.

When the air in the greenhouse becomes fully saturated with moisture this is called the `dew point’ or `saturation vapour pressure’ and this is directly related to temperature.  When the dew point is reached, free water forms on the plants and greenhouse structures in the form of condensation which needs to be avoided as it is a major disease risk.  At saturation VPD, plants stop transpiring and physiological disorders start occur.  The size of the vapour pressure deficit tells a grower how close to saturation and condensation the greenhouse environment is.

Controlling Greenhouse Humidity

Controlling the RH or VPD inside a greenhouse is relatively simple – moist air needs to be regularly vented out as the transpiration of a mature crop will bring RH levels up rapidly.  Drier air can be rapidly brought in from outside to lower RH levels on a continual basis.  If the outside air is very humid, lowering RH inside the greenhouse can be more difficult.  Low humidity levels can be rectified with use of techniques such as damping down of the greenhouse floor, evaporation pans or pads (usually installed in front of air inlets which also have a cooling effect on the air), or automatic misting or fogging.  
While misting or fogging systems are commonly used for plant propagation from cuttings and other material, in cropping greenhouses they are used to control humidity automatically usually via a number of sensors positioned in the crop canopy and greenhouse which feed data back to a central computer programme.  Misting or fogging is then automatically controlled as required to increase humidity levels to within the optimum range.  Many greenhouses use misting or fogging primarily for temperature reduction during summer, rather than to increase humidity, which in a large, healthy crop tends to run on the high, rather than low side.


Greenhouses Extend the Possibilities for a Farm

Using a greenhouse (or any other protective structure) can make it possible not only to grow things faster; but sometimes grow things that may have otherwise been difficult or impossible to grow.

Greenhouses are used to control the environment which plants grow in. The environment is extremely complex though, and there are many interactions between the different aspects of the environment. The amount of light allowed to get to plants might affect the temperature. If you close the vents or doors of a glasshouse, you may stop the temperature from dropping, but at the same time, you may be changing the balance of gasses in the air. Every time man interferes to alter one thing, he ends up altering a number of things. 

This course shows you how to use a greenhouse, shade house, cloche or other such structure; expanding your understanding and awareness of both what you might grow and how you might best grow a wide range of different crops.


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Fee Information (S2)
Prices in Australian Dollars

PlanAust. PriceOverseas Price
A 1 x $726.00  1 x $660.00
B 2 x $396.00  2 x $360.00

Note: Australian prices include GST. 
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