JOB I: Getting acquainted with greenhouses.

LESSON 1: What is a greenhouse?

OBJECTIVES:

   1.  To create an interest in greenhouses.
   2.  To develop the students understanding of a basic greenhouse.
   3.  To acquaint students with the different types of greenhouses.
   4.  To acquaint the students with the various types of bench arrangements found in the greenhouse.

MOTIVATION:

   1.  Show slides of the various types of greenhouses that will be discussed.
   2.  Provide handouts that outline the types and purposes of greenhouses that will be discussed.

STUDY GUIDES:

   1.  What is a greenhouse?
   2.  Specifically, what is the purpose of a greenhouse?
   3.  What are the most common greenhouse production crops?
   4.  What makes the framework of a greenhouse unique (as compared to other structures)?
   5.  List the common materials used for structural support in a greenhouse.
   6.  What are the most common types of greenhouse structures? What are the advantages and disadvantages to using these various structures?
   7.  What are the most common materials used for greenhouse coverings? Which covering transmits the greatest amount of light?
   8.  How do you select a covering for a greenhouse?
   9.  Within the interior design of the greenhouse, benches are used to keep the plants above ground level. What are the most important factors
     one must consider when using or constructing greenhouse benches?
  10.  What are the three most common bench arrangements used in greenhouses?
  11.  What are the three primary factors that must be considered while selecting a particular crop for greenhouse production?
 
 

ANALYSIS:

1.  What is a greenhouse?
     A greenhouse is a structure that changes the environment in order to provide optimum conditions for plant growth.

2.  Specifically, what is the purpose of a greenhouse?

The purpose of a greenhouse is:
   a.  to provide a controlled growing environment
   b.  to provide a year round growing environment
   c.  to extend the growing season of plants, especially those that go dormant (rest) during cooler weather.
   d.  to improve the quality and quantity of a variety of plant crops.

   a.  Bedding plants
   b.  Flowering plants
   c.  Flowering plants – cut flowers
   d.  Vegetables
   e.  Houseplants

     The framework of a greenhouse is unique. It must be strong and stable enough to withstand the strong natural elements, especially high winds
     and heavy snow loads. A minimum amount should be structural material so that a maximum amount of light may pass through to the plants.

     The common materials used for structural support in a greenhouse: Wood, Steel, & Aluminum. Aluminum is light and easy to maintain;
     therefore it is a common material used in the construction of greenhouses.

Types of Greenhouses
   a.  Free Span or A-Frame - single house with a strong structure, maximum light transmission, good environmental and pest control. Takes up a
     large amount of land and is expensive to heat and build.
   b.  Ridge and Furrow – looks like a couple of free-span greenhouses put together. It does not require as many building materials, land area, and
     is less expensive to heat. It is treated as one house and has good pest control. However, the environment is difficult to control when growing
     a variety of crops. It is structurally weak under heavy snows.
   c.  Quonset – This structure is inexpensive, resistant to high winds, maintains good light efficiency, and works well for seasonal crops. It is
     difficult to ventilate and requires new covering each year.
   d.  Lean – To Structures – Ideal for greenhouse hobbyists, because it can be attached to an existing structure (home) and it can use existing
     heating, plumbing and wiring. It is less expensive to build than those mentioned above. Light transmission is moderate and pests are harder to
     control.
   e.  Lath or Shade House – A modified greenhouse, that is not completely sealed. It is constructed from wood or metal supports covered with
     wood lath strips or shade-cloth (allows for filtered light transmission) which provides 50-75% shade. Its purpose is to provide protection
     from wind and sun exposure. It often serves as a holding area for retail/wholesale plants.

 7.  What are the most common materials used for greenhouse coverings? Which covering transmits the greatest amount of light?

The most common greenhouse coverings:

   a.  Glass – 90% light transmission
   b.  Fiberglass – 90-95% light transmission
   c.  Polyethylene – 65-75% light transmission
   d.  Vinyl –90% light transmission

8. How do you select a covering for a greenhouse?

Selecting the proper covering for your greenhouse is important. You must consider:

a.  The amount of light needed for the crop(s).
b.  The life expectancy of the covering.
c.  The cost of the covering as well as its maintenance.

     Greenhouse benches must allow for quick drainage, allow for maximum light exposure (no crowding), and the center of the bench must be
     accessible to greenhouse workers. Benches may be constructed out of the following materials (Note: most durable and most expensive
     materials are at the top):

   a.Corrugated transite
   b.Aluminum
   c.Wooden slats
   d.Lath (snow fencing)

   a.  Cross-Bench Arrangement: Aisles are located along the sides of the greenhouse and between the benches – least efficient use of space.
   b.  Peninsular Arrangement: Wide center aisle with enough room for carts and equipment to get through, smaller aisles between benches –
     efficient use of space.
   c.  Length-of –house Arrangement: Benches and aisles run the full length of the house – most efficient use of space.

   a.  Product quality
   b.  Production costs
   c.  Transportation costs