Greenhouses and growing structures

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Greenhouses and growing structures

• Horticulture 2

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Greenhouse

• A building characterized by the roof and walls
  made largely of glass or clear plastics, that
  provides an environment for plant growth.
• A range of greenhouse is just a group of
  greenhouse that are placed in one location

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Greenhouses come in a variety of styles.

• Even span

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2. Quonset
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3. Gothic
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4. Lean-to
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5. Contiguous
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6. Ridge and furrow
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Greenhouse coverings

• Glass- in the past, glass was the covering of
  choice. It was somewhat durable, and let in a
  high percentage of light.

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However, glass can be easily broken, and does
become brittle with age.

• Another choice was rigid plastics, like fiber
  glass. These panels have durability, and are
  inexpensive. Light transmition is good, but not
  as good as glass panels. Sun can cause
  fiberglass to yellow and chip. It is also quite
  flammable.

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Currently, the greenhouse covering most often
used is polycarbonate.

• Polycarbonates, sometime known by the commercial
  name, Lexan, is widely used in variety of
  applications. For greenhouses, it is know for
  good light transmition, strength, and even can be
  insulated to prevent heat loss.

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The last covering commonly found is poly plastic.

• Polyethylene plastic is a durable soft plastic.
  It is commonly used on temporary greenhouses, or
  seasonal cold frames. Although it can be
  effective, sun can cause deterioration of poly
  greenhouse skins in just a few months.
• So, it is inexpensive, but must be replaced
  frequently.

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Polyethylene covering on a hobby greenhouse.
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Greenhouse frames, or the skeleton of the
greenhouse come in many materials.

• Wood- the least expensive and the easiest to
  find. Redwood or cedar has the best durability,
  and lumber must not be chemically treated. Wood
  frames tend to rot, warp, and decay. To prevent
  these problems, wooden frames should be painted,
  usually white for light reflection. Painting must
  occur on a regular maintenance schedule.

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This is an example of a wooden frame greenhouse.
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Wood and steel frames-

• This framing system is not as popular as it once
  was. The combination of wood and steel was
  considered durable, but required frequent
  maintenance, like painting. It is considered
  more durable than the all wood house, but as
  mentioned, does require work.

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An example of a wooden and steel frame.
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Aluminum frames

• Most greenhouses constructed at this time have
  aluminum frames. It is durable, light weight,
  but strong. It doesnt require painting. It can
  be expensive.

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Aluminum frame greenhouse.
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Heating, cooling and ventilation of greenhouses.

• Heating, cooling, and ventilation of a greenhouse
  is essential for good plant growth. Without
  adequate air movement, and cooling systems plants
  will not flourish, and disease could follow. In
  many parts of the country, heating systems must
  be able to keep the greenhouse warm in even the
  coldest temperatures.

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Heating systems include

• Hot water heat. Hot water is circulated through
  pipes heating the air in the greenhouse. These
  pipes are commonly finned, allowing for more
  heated surface area, and better heat
  distribution.

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Steam heat is another heating system found in
greenhouses.
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One of the most common is forced hot air.These
units are hung from the ceiling of the
greenhouse. Sometimes, the greenhouse uses
convection tubes to evenly distribute the heated
air.
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Greenhouse cooling this can be done in many
ways.One of the most common is Fan and Pad.Pads
are moistened by water, and the fan behind them
cools the air that is blowing into the greenhouse.
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Greenhouses can also be cooled by evaporative
coolers.Water moves over the fan, and blown into
the greenhouse.
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To keep the greenhouse cooler in the warm spring
or hot summer months, shading clothes are often
used. These can be placed on the interior or
exterior of the greenhouse. This fabric is made
of plastic, and the grower can choose the amount
of shading required for the crop or the climate.
Shading can be done with paint as well.
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Ventilation of the greenhouse keeps the air
moving and helps keep the temperatures in the
greenhouse regulated.

• One way to ventilate the greenhouse is with roof
  or side vents. The vents open and close at a set
  temperature.

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Exhaust fans are also used to control air
movement. Some fan bring in air, and some fans
expel heated air .
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In ventilation, convections tubes are also used
to allow cool air to move throughout the
greenhouse. These clear plastic tubes often run
the length of the greenhouse. The fan at one end
keeps the tube inflated.
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Watering systems Plants need water, although
not every day. Here are some methods that
greenhouses can use to get this job done. The
first is sub irrigation. Using capillary action,
the plants are watered from below. This is
beneficial to plants like African violets, with
pubescent leaves.
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A system similar to the sub irrigation is the
system is called the ebb and flow system.
Benches are flooded with water, and when watering
is completed, the benches are drained.
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Another popular greenhouse watering system is the
spaghetti or drip system. This system uses small
tubes connected to a header. These tubes emit
gallons of water per hour. They work well
because water is not wasted, it goes where it
needs to be. However, it requires more
maintenance than other systems.
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Spray systems are another way of watering the
greenhouse. This systems waters much like a
system used to water lawns. It can be easily
installed, but some plants do not do well when
watered in this manner.
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Mist systems are commonly used in greenhouses as
well. They are frequently used on seedlings and
on newly seeded flats.
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Of course, watering can always be done by hand.
This method does take time, is sometimes
inaccurate. It is inexpensive, and anyone can do
it. Done with hose sprayer or cans, it gets the
job done.
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Lighting is another factor to consider when
building a greenhouse. Although sunlight is
preferred, supplemental lighting must be used.
In the winter, and spring this supplemental
lighting helps the plants with photosynthesis.
There are 3 main types of lighting a greenhouse.
One is high density gas discharge, another is
florescence, and the last is incandescent bulbs.
This chart shows the comparison between the
different types, and the number of bulbs needed
for the same amount of light.
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Incandescent lighting
Fluorescent lighting
High intensity gas discharge lighting
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With additional lighting, greenhouse crops can
be very successful, even in winter.
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Now for the interior of the greenhouse. Benches
are the tables that plants are placed on.
Standard industry size is 4x8, but this can
vary depending upon the growers needs. Benches
can be made of a variety of materials. Small
greenhouse may choose wood, or wood and wire
mesh, which are inexpensive to make.
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Other benches can be made of plastic. This
material is durable, easy to keep clean, and will
not warp. Plastic benches are available in many
sizes, and can be stacked.
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Commercial greenhouses often choose metal
benches. These benches can be stationary or
rolling, giving the grower many options in crop
selection.
All benches must be sturdy, easily maintained, a
comfortable working height, and of course, allow
water to easily drain.
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The last item to consider is the flooring
material. Options include, crushed rock or
gravel, concrete slab or blocks, and dirt. What
the grower needs to remember is the maintenance
of each of these floors. The greenhouse should
be a safe place to work, with all tools and
equipment stored, and should be kept weed free.
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An important part of the greenhouse is the head
house. The head house is the workspace for the
greenhouse. It should have benches for work,
bins for soil, storage for pots, tools,
fertilizers, and pesticides.
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Additional growing structures include

• Cold frames- The only heat that the cold frame
  has is from the sun. The cold frame acts as a
  halfway point for plants that have been growing
  in the greenhouse and outdoors. At this time,
  when the plants become hardened to outside wind,
  temperature, light and water fluctuations, the
  cold frame is essential.

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Shade house or Lath house

• The lath house or shade house are primarily used
  to protect plants from damaging sunlight and
  temperatures. They resemble pole buildings with
  a removable covering. They are most commonly
  found in the southern climates.

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Cold frames
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Lath house
Shade house
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Cold storage facilities are important to the
horticulture industry. Most fruits, vegetables,
and flowers are held in storage before they are
sent to market.
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Greenhouses are an important part of horticulture.