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RHS Year 2 week 11 presentation

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This document discusses protected growing structures for plants like tomatoes. It describes the benefits of growing plants indoors, such as longer growing seasons and protection from pests like blight, but also the limitations, like higher costs. Several materials used for construction frames are outlined, including their strengths and weaknesses, such as wood requiring more maintenance but having good thermal efficiency. Different glazing materials are also compared in terms of their light transmission, insulation, lifespan, and costs. The learning objectives cover the benefits and limitations of protected structures, the effects of environmental factors on indoor plants, and characteristics of construction and cladding materials.

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RHS Level 2 Certificate Year 2 Week 11 – protected growing in practice and construction materials.
Learning objectives 2.2 State the benefits and limitations of using protected structures for growing plants, (for example tomato, Lycopersicon esculentum) compared with growing the same plants outdoors. 2.3 Describe the effect of the environmental factors listed in 2.1 on plants in a protected environment. 3. Know the structural and cladding materials used for a range of protected structures. 3.1 List and describe the characteristics of a range of materials used for framework construction, including steel, aluminium, wood, and plastics. State the benefits and limitations of EACH. 3.2 Describe the properties of different cladding materials which can be used for structures, including glass; polyethylene film; polycarbonate; acrylic sheets; shade netting; and horticultural fleece. State the benefits and limitations of EACH.
Thanet Earth video – answers to worksheet  The floor is covered in white plastic to maximise light reflection inside the house which speeds ripening.  In winter heat is provided and supplementary lighting. The ventilators are not opened so carbon dioxide is also supplemented.  The lower leaves are removed so ripening fruit is not shaded  Nutrients are provided in the irrigation water (which runs out of the rockwool blocks and is recycled).  The carbon dioxide is a by-product of the heating plant  Pests are controlled by predatory insects.
Protected Growing - tomatoes  Tomatoes – Lycopersicon esculentum  Natives of South America. Tender perennials – but grown as annuals.  Raised from seed under glass – but plants ready to plant can be purchased at four sets of leaves stage.  Cordon or vine types are grown under glass and bush types outdoors.
Tomatoes in the greenhouse  Planted out into growbags or 20l containers.  Irrigation systems assist with regular even watering  Supports must be provided for cordons  Side shoots are removed as they develop.  Tap flower trusses to encourage pollination.  Remove lower leaves to prevent shading of fruit  Growing tip stopped once five trusses form.
Care of greenhouse tomatoes  Water – must be constant and evenly supplied.  Nutrients – supplied as liquid feed high in potash.  Light – shade in high summer or fruit may scorch. Otherwise clean glass and white plastic beneath containers.  Temperature – avoid cold and extreme heat. Control by ventilation, shading and damping down.
Care of greenhouse tomatoes 2  Ventilation and humidity – humidity encourages fruit set and efficient use of water. Damping down cools the greenhouse and increases humidity.  However humid conditions (particularly if the air is cool) encourages botrytis – so ventilation is crucial.  Balancing act between controlling temperature and maintaining humidity.  Carbon dioxide levels are also restored by ventilation so open vents in sunny conditions.
Pests and diseases - greenhouse  Whitefly – resistant to most pesticides. Controlled by good hygiene, fatty acid sprays and predatory insects.  Greenfly – control as for whitefly.  Blight – protected growing protects from spores (good idea to close the ventilators on warm humid nights).  TMV – buy virus free plants and don’t smoke in the greenhouse.
Tomatoes - outside  Bush varieties best suited, no need to pinch out side shoots – small varieties can be grown in cloches. Protect fruit from contact with soil.  Watering needs attention and feeding with high potash feed is required.  Planted out in late May or June when the nights start to warm up.  Very susceptible to blight – protective spraying with copper based fungicide.
Comparison of outdoor with greenhouse tomatoes Season Shorter for outdoor tomatoes Light Natural levels available – but cannot be supplemented Temperature Grow under cloches or use fleece at night – but control is limited Water Rain is available – but irrigation needed Humidity Natural levels – maintain by windbreaks Carbon dioxide Availability is not an issue Pests etc Very vulnerable to blight.
Advantages and limitations Indoor - advantages Indoor - limitations Longer growing season Close control of humidity needed Protection from blight Expense of greenhouse Protected from cold All irrigation must be provided Outdoor - advantages Outdoor - limitations Bush types – no need to pinch out side shoots Vulnerable to cold – cloches etc only limited control Less watering needed Badly affected by blight Natural levels of nutrients Shorter growing season
Construction materials – basic considerations  Thermal efficiency – important if structure is used in early spring or winter.  Strength – strong frame materials mean thin glazing bars and better light transmission  Maintenance – wood needs most, aluminium or plastic least.  Life span  Cost – cedar is most expensive, galvanised steel next.  Light transmission
Construction materials - frames  Wood – soft wood or cedar. Requires regular maintenance, cedar is expensive. Thick glazing bars but good thermal efficiency.  Aluminium alloy – little maintenance. Strong so thin glazing bars. Poor thermal efficiency.  Plastic. Short life span. Low maintenance.  Steel – usually galvanised, if not short life span. Thin glazing bars but low thermal efficiency and very heavy.
Glazing materials  Glass – horticultural or safety. Safety glass is heavier and more expensive. Good light transmission (95-97%) but poor thermal efficiency.  Polycarbonate – insulates but has less light transmission (85%). Double wall is more expensive than ordinary glass. Shorter life than glass.  Polyethylene sheeting – light transmission 89%, some insulation value, short lifespan.
Learning outcomes 2.2 State the benefits and limitations of using protected structures for growing plants, (for example tomato, Lycopersicon esculentum) compared with growing the same plants outdoors. 2.3 Describe the effect of the environmental factors listed in 2.1 on plants in a protected environment. 3. Know the structural and cladding materials used for a range of protected structures. 3.1 List and describe the characteristics of a range of materials used for framework construction, including steel, aluminium, wood, and plastics. State the benefits and limitations of EACH. 3.2 Describe the properties of different cladding materials which can be used for structures, including glass; polyethylene film; polycarbonate; acrylic sheets; shade netting; and horticultural fleece. State the benefits and limitations of EACH.

More Related Content

RHS Year 2 week 11 presentation

  • 1. RHS Level 2 Certificate Year 2 Week 11 – protected growing in practice and construction materials.
  • 2. Learning objectives 2.2 State the benefits and limitations of using protected structures for growing plants, (for example tomato, Lycopersicon esculentum) compared with growing the same plants outdoors. 2.3 Describe the effect of the environmental factors listed in 2.1 on plants in a protected environment. 3. Know the structural and cladding materials used for a range of protected structures. 3.1 List and describe the characteristics of a range of materials used for framework construction, including steel, aluminium, wood, and plastics. State the benefits and limitations of EACH. 3.2 Describe the properties of different cladding materials which can be used for structures, including glass; polyethylene film; polycarbonate; acrylic sheets; shade netting; and horticultural fleece. State the benefits and limitations of EACH.
  • 3. Thanet Earth video – answers to worksheet  The floor is covered in white plastic to maximise light reflection inside the house which speeds ripening.  In winter heat is provided and supplementary lighting. The ventilators are not opened so carbon dioxide is also supplemented.  The lower leaves are removed so ripening fruit is not shaded  Nutrients are provided in the irrigation water (which runs out of the rockwool blocks and is recycled).  The carbon dioxide is a by-product of the heating plant  Pests are controlled by predatory insects.
  • 4. Protected Growing - tomatoes  Tomatoes – Lycopersicon esculentum  Natives of South America. Tender perennials – but grown as annuals.  Raised from seed under glass – but plants ready to plant can be purchased at four sets of leaves stage.  Cordon or vine types are grown under glass and bush types outdoors.
  • 5. Tomatoes in the greenhouse  Planted out into growbags or 20l containers.  Irrigation systems assist with regular even watering  Supports must be provided for cordons  Side shoots are removed as they develop.  Tap flower trusses to encourage pollination.  Remove lower leaves to prevent shading of fruit  Growing tip stopped once five trusses form.
  • 6. Care of greenhouse tomatoes  Water – must be constant and evenly supplied.  Nutrients – supplied as liquid feed high in potash.  Light – shade in high summer or fruit may scorch. Otherwise clean glass and white plastic beneath containers.  Temperature – avoid cold and extreme heat. Control by ventilation, shading and damping down.
  • 7. Care of greenhouse tomatoes 2  Ventilation and humidity – humidity encourages fruit set and efficient use of water. Damping down cools the greenhouse and increases humidity.  However humid conditions (particularly if the air is cool) encourages botrytis – so ventilation is crucial.  Balancing act between controlling temperature and maintaining humidity.  Carbon dioxide levels are also restored by ventilation so open vents in sunny conditions.
  • 8. Pests and diseases - greenhouse  Whitefly – resistant to most pesticides. Controlled by good hygiene, fatty acid sprays and predatory insects.  Greenfly – control as for whitefly.  Blight – protected growing protects from spores (good idea to close the ventilators on warm humid nights).  TMV – buy virus free plants and don’t smoke in the greenhouse.
  • 9. Tomatoes - outside  Bush varieties best suited, no need to pinch out side shoots – small varieties can be grown in cloches. Protect fruit from contact with soil.  Watering needs attention and feeding with high potash feed is required.  Planted out in late May or June when the nights start to warm up.  Very susceptible to blight – protective spraying with copper based fungicide.
  • 10. Comparison of outdoor with greenhouse tomatoes Season Shorter for outdoor tomatoes Light Natural levels available – but cannot be supplemented Temperature Grow under cloches or use fleece at night – but control is limited Water Rain is available – but irrigation needed Humidity Natural levels – maintain by windbreaks Carbon dioxide Availability is not an issue Pests etc Very vulnerable to blight.
  • 11. Advantages and limitations Indoor - advantages Indoor - limitations Longer growing season Close control of humidity needed Protection from blight Expense of greenhouse Protected from cold All irrigation must be provided Outdoor - advantages Outdoor - limitations Bush types – no need to pinch out side shoots Vulnerable to cold – cloches etc only limited control Less watering needed Badly affected by blight Natural levels of nutrients Shorter growing season
  • 12. Construction materials – basic considerations  Thermal efficiency – important if structure is used in early spring or winter.  Strength – strong frame materials mean thin glazing bars and better light transmission  Maintenance – wood needs most, aluminium or plastic least.  Life span  Cost – cedar is most expensive, galvanised steel next.  Light transmission
  • 13. Construction materials - frames  Wood – soft wood or cedar. Requires regular maintenance, cedar is expensive. Thick glazing bars but good thermal efficiency.  Aluminium alloy – little maintenance. Strong so thin glazing bars. Poor thermal efficiency.  Plastic. Short life span. Low maintenance.  Steel – usually galvanised, if not short life span. Thin glazing bars but low thermal efficiency and very heavy.
  • 14. Glazing materials  Glass – horticultural or safety. Safety glass is heavier and more expensive. Good light transmission (95-97%) but poor thermal efficiency.  Polycarbonate – insulates but has less light transmission (85%). Double wall is more expensive than ordinary glass. Shorter life than glass.  Polyethylene sheeting – light transmission 89%, some insulation value, short lifespan.
  • 15. Learning outcomes 2.2 State the benefits and limitations of using protected structures for growing plants, (for example tomato, Lycopersicon esculentum) compared with growing the same plants outdoors. 2.3 Describe the effect of the environmental factors listed in 2.1 on plants in a protected environment. 3. Know the structural and cladding materials used for a range of protected structures. 3.1 List and describe the characteristics of a range of materials used for framework construction, including steel, aluminium, wood, and plastics. State the benefits and limitations of EACH. 3.2 Describe the properties of different cladding materials which can be used for structures, including glass; polyethylene film; polycarbonate; acrylic sheets; shade netting; and horticultural fleece. State the benefits and limitations of EACH.