Protected Plant Production

Lesson Structure

There are 8 lessons in this course:

1. Structures for Protected Cropping
2. Describe and Evaluate the type and shape of modern growing structures.
3. Environmental Control
4. Cladding Materials and their Properties
5. Irrigation and Nutrition
6. Relationship between Production techniques and Horticultural practices
7. Harvest and Post Harvest Technology
8. Risk Assessment

Aims

• Describe and Evaluate the type and shape of modern growing structures
• Describe and evaluate environmental controls in protected cropping
• 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 for a protected crop

What You Will Do

• 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 a situation
• 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 pre and post harvesting treatment of the crop
• State the factors to be considered when marketing crops
• Evaluate alternative marketing outlets
• Relate packaging & 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

Choosing a Structure for Protected Growing

It all depends upon what you plan to use it for:

• What you will grow (type of plants)
• How many plants you plan to grow (scale of operation)
• Stage of growth (propagating, growing on young plants, or growing plants through to full maturity)

Example -If You plan to Use it for Propagation

You might not need a huge greenhouse to get started with propagating plants (even on a commercial basis). You can do a great deal in a small space in a propagation greenhouse. As this article shows, greenhouses come in all shapes and sizes.

Greenhouses and other Propagating Structures

A greenhouse is any type of walk in building, which maintains an atmosphere suitable for good plant growth. The warm, humid environment is ideal for propagating plants, hastening and improving seed germination and root initiation in cuttings.

The main types of greenhouses are as follows:

• Glasshouse: A greenhouse with glass walls (at least in part). They are very effective for propagating plants and are long lasting but expensive. They are generally free-standing, although lean-to glasshouses can be attached to a blank wall of a house. Glasshouses can be bought as DIY kits, which can be easily assembled.

• Fibreglass house: A greenhouse clad with fiberglass sheets. Compared to glasshouses, they are cheaper, have a medium lifespan and comparatively poor insulation.

• Coreflute/Solar sheet houses: These are medium cost, have a medium lifespan (15 years plus) and give more effective temperature control than PVC or fiberglass. 

• PVC Film (Polythene houses): These are covered with a polythene film over a metal framework (usually a tunnel). They are very cheap, with the PVC lasting only a few years before replacement. They have the poorest insulation properties of all the greenhouses.

Cold frames and shade houses are also used for propagating plants. A cold frame consists of a wooden, metal or brick frame with a removable or hinged glass, plastic or fiberglass cover. It provides sheltered conditions for striking cuttings and germinating seed, and can be placed out in the open or inside the greenhouse. A simple cold frame can be built for a very low cost and can be used effectively to strike cuttings or germinate seed (though not always as effective as other structures).
 
Shade houses are used for protecting young plants usually after removal from the propagating area and planting up into the first container. They allow plants to be gradually "eased" out of their highly protected propagating environment into the harsher conditions outside. They are also used for permanent protection of plants that prefer more shaded conditions, such as many ferns and rain forest plants.

Buying a Greenhouse for Propagation

Most hobbyists start off with kit glasshouses, and there is a wide range of sizes and shapes available. As well as cost, also consider the following before you buy a greenhouse:

• Size and shape: Straight-sided greenhouses are the most versatile, allowing good use of space. Think about whether you will be actually working in the greenhouse (in which case you will need a tall greenhouse), or whether you will be sowing the seed, etc. elsewhere (in which case a tunnel house can be used).
• Durability: The most durable greenhouses are glasshouses with aluminium frames. Other cladding materials have varying durability (see above) but are considerably less expensive. 
• Maintenance: Replacement of cladding is the major maintenance requirement. Glass, although more durable, still needs maintenance. In summer, it needs to be covered with shadecloth or whitewash paint to prevent overheating. Any remaining paint should be cleaned off in winter. The glass will also need to be kept clean of algae and dirt, which reduce incoming light.
• Ventilation: Glasshouses can quickly overheat in warm weather so make sure there are adequate roof and wall vents. These can be opened manually or automatically.
• Hygeine: Good hygiene is essential for propagating plants so think about how easy it will be to keep the structure and equipment clean.

Equipping a greenhouse for propagation

Benches

Benches enable plants to be raised off the greenhouse floor, keeping them away from disease and often in better light. A tiered system of benches also makes better use of space, and saves bending your back. They can be made out of metal, wood or plastic, and may be slatted or solid in construction, but must drain freely. Wooden benches should be used with caution as they are prone to rotting and may become infested with pests such as ants or mealy bug. Capillary matting (a continually moist, absorbent material, sold by some greenhouse companies) can be used to cover the bench to reduce the need for watering.

Hot Beds

These are similar to cold frames, except that they provide bottom heat (in a box arrangement) for striking cuttings and germinating seed. Heat is provided in the base of the bed by means of electric heating cables, hot water or steam pipes, or hot air flues. Electric heating is generally most suitable for the hobbyist. The bed needs to have drainage outlets and should be made from a material which will not rot (ie. brick, concrete, treated timber).  An ideal size is around 1 m x 2 m. The hotbed is filled with 8 to 15 cm of coarse propagating sand or perlite. Hot bed units (sometimes called heated propagators) can be purchased from glasshouse and nursery suppliers.

Mist Systems

These involve a series of mist-producing sprinklers, which spray the cuttings/seeds at controlled intervals. They maintain a fine film of moisture over the leaf surface, preventing wilting and hastening root emergence. The misting can be controlled by timers or by automatic sensors, which prevent the propagation medium becoming too wet.

Fluorescent Light Boxes:

Plants of many species propagate well under artificial light. The cool white fluorescent tubes are preferable.
 

Tents/Bell Jars

Plastic tents (hung over a wire frame) can be used to further increase humidity and air temperature in a greenhouse over plants that may do better in a very humid environment.
Large Bell Jars can be used to do the same over individual containers of seed or cuttings.

Heaters

Heating is only needed during winter in cooler areas. Thermostatically controlled electric fan heaters are available which are specifically designed for greenhouses. Solar heaters can also be used, although they may need to be used in conjunction with a backup heater.
Insulated cables, similar to those used in hot beds, can be used for warming benches if only a small amount of heat is required.

Cooling fans

Exhaust fans are used to cool the greenhouse. They are placed at the end of the greenhouse, opposite the main entry door, which is left open to improve air circulation.

Irrigation

Some owners opt for installed irrigation sprinklers on automated systems whereas other home propagators and gardeners prefer hand watering as it allows them to maintain a 'personal connection' to the plants.