LIGHTING AND TEMPERATURE

Plants respond to the relative lengths to light and dark periods as well as to the intensity and quality of light. Artificial light has been used extensively to control plant growth processes under various conditions. Plants differ in the need for light; some thrive on sunshine, others grow best in the shade. Most plants will grow in either natural or artificial light. Artificial light can be used in the following ways:

•To provide high intensity light when increased plant growth is desired.

•To extend the hours of natural daylight or to provide a night interruption to maintain the plants on long-day conditions.

Proper lighting not only extends the gardening day by enabling the gardener to work in the greenhouse during the dark evenings of winter and early spring, but it aids plant growth. Three basic types of lamps used in greenhouse lighting are:

Fluorescent lamps - These have the advantage of higher light efficiency with low heat. This type of lamp is the most widely used for supplemental light. It is available in a variety of colors but cool-white lamps are the most common. High intensity (1500 ma) fluorescent tubes that require higher wattage are also commonly used to reach 2000 foot candles. - These have the advantage of higher light efficiency with low heat. This type of lamp is the most widely used for supplemental light. It is available in a variety of colors but cool-white lamps are the most common. High intensity (1500 ma) fluorescent tubes that require higher wattage are also commonly used to reach 2000 foot candles.

Incandescent lamps - These vary in size from 60 watts to 500 watts. They are used to extend day- length in greenhouses. The grower can vary foot- candle levels by adjusting the spacing and mounting height above the plants. These vary in size from 60 watts to 500 watts. They are used to extend day- length in greenhouses. The grower can vary foot- candle levels by adjusting the spacing and mounting height above the plants.

High-intensity discharge (HID) lamps - These have a long life (5000 hours or more). With improvements made possible by the addition of sodium and metal-halides, the lamp has a high emission of light in the regions utilized by plants. These have a long life (5000 hours or more). With improvements made possible by the addition of sodium and metal-halides, the lamp has a high emission of light in the regions utilized by plants.

Light Meters - Inexpensive light meters are available for measuring the light intensity. The most common light meters are calibrated in foot candles (1 ft cd =10.76 lux). Foot candles should be measured at the growing level of the plants. Research your particular type of plant and find out what the optimum foot candles are for growth or propagation. Adjust your light height accordingly so that the the foot candles are correct at the growing level when measured with the light meter.

LIGHT INTENSITY METER

Measure the number of foot-candles from sunlight or grow lights to create the optimum growing conditions for your plants.
Information booklet with recommendations included. No batteries required. GS-775

Temperature - As a gardener you will be concerned with 2 temperatures - the air temperature required in the greenhouse and the minimum outside temperature that your heating equipment must overcome. For most plants, a night temperature of 60 to 65 degrees F in the greenhouse is adequate. The general rule, however, is not to have a higher temperature than is necessary. If you grow some plants that require a higher temperature than is provided in the greenhouse, use a propagating case or a warmed bench with thermostatically controlled warming cables to warm the air surrounding the plants. This can be done at a fraction of the cost that would be necessary to heat the whole greenhouse to provide the same temperature. As a gardener you will be concerned with 2 temperatures - the air temperature required in the greenhouse and the minimum outside temperature that your heating equipment must overcome. For most plants, a night temperature of 60 to 65 degrees F in the greenhouse is adequate. The general rule, however, is not to have a higher temperature than is necessary. If you grow some plants that require a higher temperature than is provided in the greenhouse, use a propagating case or a warmed bench with thermostatically controlled warming cables to warm the air surrounding the plants. This can be done at a fraction of the cost that would be necessary to heat the whole greenhouse to provide the same temperature.

If you want a temperature of 60 degrees F, install heaters that will provide that temperature. If you want no more than frost protection, set the thermostat at 40 degrees F. Space heaters can maintain a minimum of 60 degrees F in the greenhouse. Higher temperatures on plant benches can be provided with soil-warming equipment.

Remember that heat is lost from a greenhouse by radiation, conduction, and convection through:

• Glass.

• Walls and other non-glass parts of the structure.

• Floor or soil.

• Ventilation, door openings, and cracks.

• Choose your greenhouse covering carefully.

---

CO₂ Control

Carbon dioxide (CO₂) and light are needed for plant growth. Closed greenhouses often have too little carbon dioxide during the day to effectively utilize available light. Therefore, plants grow poorly when air vents are closed. By enriching the atmosphere with CO₂, plant growth can be accelerated. Because light and carbon dioxide complement each other in plant growth, additional electric lights for greenhouses combined with good carbon dioxide control will increase yields of lettuce, tomatoes, orchids, chrysanthemums, carnations, snapdragons, geraniums, and other crops.

CO₂ equipment utilizing infrared sensors is available for greenhouse owners who want to benefit from carbon dioxide enrichment with supplementary lighting. The equipment will measure and control CO₂ levels from 0 to 2,000 parts per million which will satisfy most of the production needs of greenhouse growers. This equipment is fairly expensive and requires frequent calibration. Inexpensive color metric kits are also available for determining the CO₂ levels in your greenhouse.

Forms of CO₂

Forms of CO₂ for enriching greenhouse atmospheres follow:

•Bottled CO₂, which has been liquefied from a burning process. This liquid carbon dioxide is kept under pressure and is controlled by means of a solenoid or metering device.

•Dry ice, which may be placed in a greenhouse or growth chamber in block form or placed in a converter (a pressure bottle) and stored until needed.

•Burned sulfur-free gaseous fuels such as natural gas, LP gas, or a liquid carbon fuel such as kerosene.

"EnviroCept R-Value Paneling Compared To Other Popular Greenhouse Coverings"

Accelerates plant growth, +Insulation of 2.1R 2.3R, +Transmits 70-75% diffused tight, +Strong, durable, and flexible, +Chemical and mildew resistant, +Extends growing seasons, +Easy to handle and apply, +Not affected by temperature extremes, +High quality paneling at an affordable price!

***

Control Units:

Automatic controls are important. Without them, switching lights, fans, pumps, heaters, and misters on an off at a prescribed time would be a complicated and laborious task. Many time clocks, photo cells, thermostats, and other controls are available commercially. When used individually or in combination they will provide any time interval or control desired.

To Learn More About Planning Your Greenhouse Select Your Area of Interest by 'Clicking' on the Index Text Below.

TYPES OF GREENHOUSES & CONSTRUCTION

GREENHOUSE BASIC DESIGN & LOCATION

GREENHOUSE COLD FRAMES, HOTBEDS & PROPAGATING FRAMES

HEATING A GREENHOUSE

GREENHOUSE VENTILATION & COOLING

EnviroCept UV GREENHOUSE GLAZING PANELS