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R2114 > Growing undercover > Flashcards

Growing undercover Flashcards

1
Q

What factors vary between the environment with a protected structure and that outside it?

A 
Temperature
Co2 levels
Light
Relative humidity
Pests
Soil water
Wind speed
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2
Q

What is a cloche?

A

A portable unit made of glass, rigid plastic, or sheet plastic stretched over a frame to protect plants or advance growth.

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3
Q

Pros & Cons of a polythene tunnel?

A

Need to be anchored firmly as can be blown away.
Creates a large growing space, for less cost than a greenhouse.
Easier to relocate than a greenhouse.
If polythene cover is damaged it will all need replacing.
Doesn’t let as much light through as a glass greenhouse.
Can contain crop bars - steel bars at head height which you can hang hanging baskets.

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4
Q

Pros & cons of a conservatory?

A

Usually attached to a house, and is centrally heated.
Can be extremely hot or extremely cold.
Main use is for humans, so environment not always ideal for plants. Too hot, dry.
Good for houseplants, tender perrenials, succulents, orchids and for starting off seedlings. Cuttings.
Can be limited light, as light can only enter from one side.

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5
Q

What is an alpine house?

A

An alpine house is used to display and protect alpine plants.
It is not heated.
More ventilation than an ordinary greenhouse.
Key is to prevent plants from getting waterlogged in winter. They don’t mind the cold.
Reduced risk of fungal disease.

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6
Q

What is the ideal humidity rate for most plants?

A

40-75% relative humidity

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7
Q

What are the pros and cons of wooden framework?

A

Cedar is more durable than pine and can last 10-25 years. Teak & mahogany are hard wood, but environmentally unsustainable.
Wood is a better insulator than aluminium or steel.
Wood is a natural material so looks more in keeping with garden.
Cons are it needs maintenance treating regularly with preserves, not as durable as aluminium, plastic or steel as will eventually rot. Also generally thicker than steel or aluminium so will block light.
More expensive than aluminium or plastic.

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8
Q

What are the pros and cons of aluminium?

A

Silver usually, but can be painted different colours and is better looking.
Frames are longer lasting than wood.
Cheaper to buy than wood.
Allow more light in as thinner than wood.
Low maintenance.
Long lasting and durable.
Poor insulator.
Less aesthetically pleasing than wood.
Lightweight so can blow away if cladding is also lightweight - eg. polycarbonate.
Not as strong as steel, bends more easily.

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9
Q

What are the pros and cons of steel?

A

Usually galvanised so has a grey coating.
Exceptionally strong, commonly used for polytunnels.
Also used in Venlo’s in the roof support system and stanchions.
Very durable.
Low cost and low maintenance.
If coated does not oxidise.
Heavier than aluminium.
Not commonly used in greenhouses. Steel will bend.
Less attractive in residential settings.

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10
Q

What are the pros and cons of plastic?

A 
Can be used for all structures.
Low maintenance, and durable.
Used for all different shapes.
Light so needs firm anchorage.
Not bio degradable.
Degraded by UV light.
Expensive compared to aluminium.
Less beautiful than wood. Coloured plastics are expensive.
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11
Q

Pros and cons of horticultural glass as a cladding material?

A 
Long lasting, but shorter than toughened glass.
Good light transmission.
Good heat retention.
Very scratch resistant, although can be scratched which affects light transmission.
Heavy.
Strong but breakable.
Low maintenance. 
Cheaper than toughened glass.
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12
Q

Pros and cons of Safety glass as a cladding material?

A 
Long lasting, wind resistant.
Tougher than horticultural glass.
Thicker than horticultural glass, so lower light transmission.
Heat retention reasonably good.
Can be coated so even more scratch resistant.
Strong resistance to breaking.
Weight heavier than horticultural glass.
Expensive.
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13
Q

Pros and cons of Polythene as a cladding material?

A 
Light weight
Flexible.
Less expensive than glass.
Can be treated with chemicals  to change properties.  Good for specific crops.
Limited lifespan.
Poor light transmission compared to glass.
Can be easily vandalised.
Can blow away!
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14
Q

Pros & cons of polycarbonate cladding material?

A

Shorter lifespan than glass, but longer than polythene.
Can be 10-20 years.
Can easily be cut to shape with a saw.
Good light transmission.
Excellent heat retention - particularly if twin walls.
Strong & light.
Expensive.
Often yellows over time so affects light transmission.

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15
Q

Pros & cons of acrylic sheets?

A 
Used for cloche or greenhouse.
15 years lifespan.
Can be moulded into shapes/curves.
Good light transmission.
Can be drilled.
Lighter than glass.
Reduction in light transmission over time due to scratches.
Can cost more than polycarbonate.
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16
Q

Pros and cons of shade netting?

A 
Lifespan up to 10 years.
Used in a shade tunnel.
Various degrees of shading to suit crops.
tear resistant.
Maintains a lower temperature.
Reduces photosynthesis.
Prevents excessively high temperatures.
Costs more than polycarbonate.
Low maintenance.
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17
Q

Pros and cons of horticultural fleece?

A 
Short lived.
Heat retention is good.
Economical.
Flexible.
Doesn't need strong framework, can be pegged down.
Not long lived or weather resistant.
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18
Q

What are the top 3 glasshouse designs for allowing maximum winter light?

A
  1. Curvilinear
  2. Mansard
  3. Dutch light
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19
Q

What is the best orientation for a greenhouse in northern hemisphere?

A

Ridge of greenhouse runs East to West. Sun from the south will hit one side of the sloped roof for higher penetration of light.
Also less shadows from the structure are cast over the greenhouse.

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20
Q

What should you consider when positioning a greenhouse?

A

Don’t position underneath trees or near buildings where they will cast shadows and block light.
Honeydew from insects on trees can cause sooty mould and therefore block light.
Leave 1 metre space around the outside of the structure, so you can get in to clean and maintain.
Convenient access - near to house, but not too near!

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21
Q

Why use supplementary lighting?

A

Extend season - eg. maintain summer type 14 hour days light.
Extend day length - eg create a 12 hour day in the middle of the winter.
Increase the quantity of light when natural levels are low. over cast days or winter.
Change the type of light - vegetative growth or flowering growth respond to blue and red respectively.
Allows work to be carried out in the greenhouse at night.

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22
Q

Why use shading?

A

Reduce light levels for shade loving plants. Such as ferns, or seedlings or lettuces.
Reduce temperature eg. Cyclamen persicum
To manipulate the photo period eg shorten the day length eg. for short day plants such as poinsettia so that flowering is initiated. If left to their own devices they’ll flower too late for Christmas!

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23
Q

What symptoms will plants show if not getting the enough light?

A

Etiolation - long and stretched with longer internodes.
Pale yellowing leaves.
Thin leaves.
Smaller leaves.

24
Q

What symptoms will plants show if not getting too much light?

A

Colour of leaves may appear bleached.
Foliage can turn brown and shrivel
Leaves can become small and curled at the edges.
Too much light often linked to higher temperature too.

25
Q

What does red light do?

A

Red lights cause plants to become tall and leggy at the vegetative stage. But good for growers if you want to encourage flowering.

26
Q

What does blue lights do?

A

Blue light can cause plants to grow low, compact and stocky – this can be useful in the vegetative stages to produce lots of leaves and a compact plant

27
Q

Give 4 examples of types of lamps?

A
  1. HID (High intensity discharge)
    Not as efficient as LED. Examples – sodium, metal halide and mercury
  2. LED lights becoming more common
  3. Fluorescent- give a mix of warm and cool light - good for working in.
  4. Incandescent (uses electricity to heat a filament)
28
Q

Define the term cladding material?

A

The material used to cover the framework of the structure so that it is suitable for the growth of protected crops.

29
Q

How can you reduce light in a protected environment?

A

Shade netting can be used inside or outside the structure. Reflects light away in summer reducing the heat and light levels. In winter reflects heat back into glasshouse insulating it.
Outside can be prone to algae/dirt. Inside less effective at reducing the heat.
Flexible.
Can be installed manually or automated blinds.
Life expectancy several years.
Shade paint - although more difficult to remove.

30
Q

How to grow Poinsettia undercover?

A

Poinsettia’s are raised by cuttings bought either as rooted or unrooted.
They need 4 week period of 12 hour days to initiate flowering. Naturally would occur after Christmas. In order to force them to flower in time for Christmas, growers manipulate the light from late September. Use blackouts to give them a 12 hour night. Flowering then begins in November, and they’re ready for the shops early December.

31
Q

Methods to achieve the optimum temperature?

A

Heating methods to maintain temperature.
Cooling methods to reduce temperature.
Insulation to reduce heat loss.
Close monitor of temperature for fast action
Heat can be generated using various fuel sources.

32
Q

How can you reduce heating costs as it’s expensive?

A

Improve insulation.
Reduce external wind speed with a wind break.
Maximise light transmission, as this will create heat.
Accurate control of heating system.
Divide the protected structure into sections, and only heat where necessary.
Choose more thermally efficient cladding.
Reduce air leakage with better fitted cladding.

33
Q

What sort of heating system suits a small greenhouse?

A

Electric as they are more efficient.

34
Q

What sort of heating system suits a large greenhouse?

A

Gas or oil heating systems.

35
Q

How does a gas fired heater work in a greenhouse?

A

Heats water and pumps it through pipes which can be ground level, bench level or above.
Can be mains gas or bottled propane gas.
One of the least expensive methods of heating a greehouse.

36
Q

What are the limitations of gas heating system?

A

Using non renewable resources.
Carbon emissions.
May be difficult to control.
May produce toxic fumes so ventilation is vital.
Therefore loss of heat.
Co2 emissions.
Need to be monitored as can be dangerous to people working in them.
Used for 30m square plus sized greenhouses.

37
Q

How does an electric/fan heater work?

A

Used for small greenhouses where high temperature not required.
1-2 fan heaters.
Need electric mains supply in greenhouse.
Expensive, but no danger of toxic fumes, so no need to ventilate. Therefore less heat lost through ventilation.
More easily controlled, but will be a dry heat next to plant nearest. Hard to distribute heat evenly.
Will lower relative humidity, so you may need to water more frequently.
Heating element can be turned off in summer, and used as a cooling fan instead.

38
Q

How does electrical convection work?

A

Like a house radiator!
Electrical tubular heaters produce slow convected heat evenly.
More gentle heat, so less likely to damage plants than fans.
Good for greenhouses that have misting systems, as heating elements are encased.
Cheaper to install than a traditional hot water system.
less economical to run in large greenhouse.
Limited to medium / small greenhouses.

39
Q

How do electrical cables work?

A

Soil warming mats/cables that run through sand or beneath growing medium or under the greenhouse floor.
Requires electric connection to mains. Economical, uniformed heat. Less wasted, as can target plants such as sown seeds or cutting that need bottom heat.

40
Q

How does a biomass boiler work?

A

Same as a gas/oil burner boiler but burns wood, logs, pellets.
Usually larger and needs constant supply of biomass.
Expensive to install.
Seen as carbon neutral, as the carbon emitted is equal to the amount absorbed over months and years trees were living. Provided they’re all replaced with new trees.

41
Q

Name 4 methods of cooling a greenhouse?

A

Forced ventilation
Natural ventilation
Evaporation
Shading.

42
Q

Describe forced ventilation?

A

An extractor fan sucks the warm air out, and cool air is drags in through vents. Fan blows cool air into green house.
Costly.
Can be sealed system, so pest and disease access is reduced compared to natural ventilation.
If sealed, may need Co2 enrichment.

43
Q

Describe Natural ventilation?

A

Used in tunnels, ends and doors open to allow natural air flow through.
Slide vents or doors opened to allow cool air in, and roof vents, allowing hot air to rise up and escape.
Raise the sides of a polytunnel.
Weather dependant.
Can be automated with roof vents.

44
Q

Describe evaporation technique?

A

Damping down and misting will reduce the temperature.

45
Q

Describe shading technique?

A

Used in a domestic setting. Lowers light and therefore reduces the heat. Shade netting over a polytunnel, or greenhouse inside or outside. Shade paint.
Screens can be automated whereas shade paint not so flexible.

46
Q

What is relative humidity?

A

Relative humidity (RH) = Relative humidity is the amount of water vapour in the air relative to the total amount of water the air can hold at a given temperature.

47
Q

What are most plants ideal relative humidity?

A

40-75%

The higher the temperature the lower the relative humidity is.

48
Q

How to control relative humidity?

A

Heating - raising the temperature will reduce the relative humidity.
Damping down or misting will increase the relative humidity.
A heating system that circulates air will increase ventilation and further reduce humidity.
Ventilation will also reduce the relative humidity as air often outside is lower RH ie. drier.

49
Q

What are the 4 functions of ventilation?

A

Cooling down in summer.
Humidity levels year round.
Co2 control year round.
Prevention of disease.

50
Q

Name 4 different types of irrigation

A 
Watering can (manual)
Hose pipe (manual)
Drip systems (mainly containers, but open ground too.)
Seep hose
Tube dripper system for pots.
Capillary system (containers)
Overhead sprinkler system (automated)
51
Q

Describe watering can method and it’s pros and cons?

A

For smaller areas. Various rose capacities.
More flexible in amount given to each plant.
Can use grey water or rain water from water butt.
Water can be aimed at root zone, so lower risk of fungal disease.
Labour intensive.
Only feasible for small areas.

52
Q

Describe hosepipe method of watering and pros and cons.

A

Can have lance fitted to alter flow like watering can.
No time wasted refilling a watering can.
Can be specific about how much to water each plant, if done manually.
Can be attached to a sprinkler and be on a timer.
Trip hazard. Difficult to manoevre. Requires mains supply. Easy to overwater. Difficult to use harvested rainwater.

53
Q

Describe an automated drip system and pros and cons.

A

Mainly used in containers, but can be used in open ground.
Pipes deliver water directly to plant at base of the stem. Network of pipes connected to branching tubes which can be sunk into each container. Held in place with pegs.
Can be automated with a timer.
Less water waste.
Water can be directed to root zone.
Nozzles can get blocked by impurities.
Can’t use grey water or rain water.
Expensive to install but will last years.

54
Q

Describe seep hose system and pros and cons.

A

For borders, a type of soil soaker hose a type of drip/trickle irrigation. Hoses are porous, so water seeps out along wherever it’s laid.
Regular and more even plant watering.

55
Q

What is a capillary system?

A

A type of sub irrigation for plants in containers only. 2 types of capillar systems. Matting or sand.
Deep bench lined with heavy plastic and then wet sand. Plant containers must have holes in. Sand kept constantly moist. Doesn’t work with clay pots as they wick the moisture.
Capillary mat - heavy felt like material placed over a plastic sheet. Mat is continually wet and containers sit on top.
Potting media must be specific to that plant so that it has optimum water holding capacity
Capillary mats often the site of algal growth which must be controlled.

56
Q

Describe an overhead irrigation system, and the pros and cons?

A

A network of rigid overhead pipes, with mini sprinklers or nozzles at various points. Anti drip nozzles installed to prevent large drips on plants beneath.
Good for large space and flexible.
Wet foliage can encourage disease.
Can be automated with a timer.
Water can be wasted if plants widely spaced.

R2114 (6 decks)

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