1 - Types of Protected Environments Flashcards
Name 5 kinds of protective environments and give examples of their purpose.
Greenhouse: used for the propagation and production of long main season crop of tomatoes or for the production of cut flowers
Cold frame: used for the propagation and production of young vegetable crops (e.g. cabbages) and for hardening off bedding plants
Polythene tunnel: used for growing self-branching celery crops or the production of lettuce
Cloche: used to advance ripening of crops. e.g. strawberries. Or covering taller crops while they establish.
Conservatories: used to display flowering or foliage plants at home.
What is a cloche?
A small, temporary and movable cover for crops. Traditionally glass, but most are light plastic now.
What is a tunnel cloche?
Often polythene or other plastic stretched over hoops and held in place by pegs. Can be simple or elaborate. Covers a row.
What is a cold frame?
A low box in which plants can be propagated and grown. Can be covered with lights, glass or polycarbonate covers, or left open. Should be sited in shaded, frost-free areas. Optimum size 1.2m x 60cm.
What is a polythene tunnel?
A large walk-in structure that’s an alternative to a glasshouse. Plastic skins on a metal structure, usually. Cheaper to purchase and erect. Keep out the worst winter cold and protect against strong wind. May have irrigation and heating. Often have poor ventilation. Plastic needs replacing every few years.
What is a glasshouse?
Either free-standing or lean-to structure. Often made of aluminium or wooden frames, containing sheets of horticultural glass or even polycarbonate these days. Roof sloping to let sun in efficiently. Can be relatively simple or very complex, with ventilation, heating, fans, irrigation systems, etc.
What is a conservatory?
A more ornate structure than a glasshouse, generally attached to a wall and designed for the comfort of people. Generally used to display rather than grow plants. Suitability for growing plants can vary.
What are the advantages and disadvantages of using glass in protected environments?
Advantages:
- Allows best light transmission (up to 90%)
- Easy to clean
- Does not deteriorate or scratch easily
Disadvantages:
- Heavy
- Fragile
- Can be dangerous.
What are the advantages and disadvantages of using polycarbonate in protected environments?
Advantages:
- Good insulation qualities as double skinned with air pockets between
- Does not shatter so safe for use in public areas
Disadvantages:
- Gives less light transmission than glass (only 75%)
- It is expensive
- Scratches, although generally lasts a long time.
What are the advantages and disadvantages of using Polythene in protected environments?
Advantages
- Relatively inexpensive product
- Good light transmission, similar to glass when new
- Light weight, so requires less framework, allowing more light transmission
Disadvantages
- Deteriorates in the sun and becomes cloudy, reducing light transmission
- Can rip and be holed
- Needs to be replaced every 3 - 4 years.
What are the advantages and disadvantages of using acrylic sheets in protected environments?
Advantages:
- Does not shatter so safe for use in public areas
- Good light transmission similar to glass
- Can be moulded to shapes, such as curves
- Can be drilled
Disadvantages
- Can scratch
- Poor heat retention
- Really only lasts usefully for 2 - 3 years, even though shelf life is much longer.
What are the advantages and disadvantages of using aluminium framework in protected environments?
Advantages
- Light weight, strong enough for glazing, etc
- Low maintenance and corrosion resistant
- Glazing bars thing so allows good light transmission
Disadvantages
- May not be strong enough for structural supports
- Does not retain heat well
- Not aesthetically pleasing
- Expensive
- Does not weld.
What are the advantages and disadvantages of using galvanised steel frameworks in protected environments?
Advantages
- Can be welded
- Low maintenance
- Very strong
- Long lasting
Disadvantages
- Difficult to shape
- May rust where cut or bolted
- Heavy
- Expensive.
What are the advantages and disadvantages of using plastic framework in protected environments?
Advantages
- Cheap
- No problems with rust or rot
- Low maintenance
- Easy to cut
- Light weight
Disadvantages
- Short-lived and easy to break
- Unattractive.
What are the advantages and disadvantages of using wooden framework in protected environments?
Advantages
- Easy to cut and join
- Warmer, less heat required
- Looks aesthetically pleasing
Disadvantages
- Requires high maintenance
- Wood has to be thick to be strong, cutting out light and causing shadow effect
- Wood eventually rots and can warp.
