Chapter 19 Greenhouses and Other Growing Structures

Chapter 19: Greenhouses and Other Growing Structures OBJECTIVES: List the purposes of a greenhouse. List and describe the types of greenhouse structures. List the common types of greenhouse covering materials. Describe greenhouse heating, cooling, and ventilation. Describe greenhouse benching.

The 3 purposes of a greenhouse: To provide a controlled growing environment for plants whose value justifies the expense. To permit the growth of plants in regions where survival outdoors is not possible. To extend the season of growth for plants at times when they would normally go dormant.

Types of Greenhouse Structures: Detached A-Frame: Provides the best environmental control; is the most expensive to build and heat.

Types of Greenhouse Structures: Quonset: Ideal for production of seasonal crops; requires new covering every year.

Types of Greenhouse Structures: Ridge and Furrow: less expensive to build due to lack of interior walls; good environmental control.

Types of Greenhouse Structures: Lath or shade house: provides a shaded area for production of heat sensitive plants.

Types of Greenhouse Structures: Hotbed or cold frame: a low growing structure that supplements solar energy with decomposing manure, electric cables, and heating pipes; used for propagation, starting, and hardening off.

The common types of greenhouse cover materials: - glass - fiberglass - soft plastic shade fabric polycarbonate acrylic

Some plastic-covered greenhouses have 2 layers of plastic with inflated air space in between. Advantage: makes covering more airtight and more heat-retentive. - Disadvantage: reduction of light intensity.

Greenhouse Heating: The greenhouse wall that is an energy liability is the North because no direct sunlight hits it. Most of the heat loss in a greenhouse occurs after dark. Therefore, fuel consumption in a greenhouse is greatest after dark.

Greenhouse Cooling: Fan and pad cooling - Uses exhaust fans and continuously wet pads of excelsior, cross-fluted cellulose, aluminum fibers, or glass fibers.  Fog evaporative cooling - Uses a high pressure pump to create a fine mist whose water droplets are so tiny that they remain in suspension in the air, then evaporate.

Greenhouse Ventilation: Greenhouse ventilation systems bring fresh air into the greenhouse to replace the warm internal air. During especially hot weather, ventilation alone may not be enough.

Greenhouse Benching: Greenhouse benches must fulfill 3 functions: Drain quickly. Be of a width that allows workers to reach the center. Maximize crops exposure to light.

Greenhouse Benching: The style of benches depend upon the crop being grown. Examples of crops that are grown on ground beds: Tomatoes and lettuce. Examples of crops that are grown on raised benches: Pot crops and cut flower crops. Raising the bench above ground has 2 advantages: Allows air flow; allows warmer root zone temperatures to be maintained.

Greenhouse Benching: 2 types of wood are recommended for wooden bench use: Naturally rot resistant Preservative treated woods

Greenhouse Benching: 3 greenhouse bench arrangements: Cross-bench arrangement Aisles along the sides and between the benches; least efficient use of space for growing. 

Greenhouse Benching: 3 greenhouse bench arrangements: Peninsular benching Each bench his accessible from both sides and the aisle end. Features a wide central aisle to accommodate carts and other equipment; narrow aisles between benches allow access by workers and efficient use of space.

Greenhouse Benching: 3 greenhouse bench arrangements: Length of house benching Uses growing space efficiently; workers must walk the length of house to get to the other side of bench.

Chapter 19: Greenhouses and Other Growing Structures OBJECTIVES: List the purposes of a greenhouse. List and describe the types of greenhouse structures. List the common types of greenhouse covering materials. Describe greenhouse heating, cooling, and ventilation. Describe greenhouse benching.