Resource Book on Horticulture Nursery Management

water is often too costly and may contain harmful fluoride. Pond or river water is subject
to disease organisms and may require expensive chlorination.
Orientation: The greenhouse frame casts shadows. The magnitude of the shadows
depends upon the angle of the sun and thus upon the season of the year. The latitude and
altitude of the area should be considered while selecting the site because it affects light
and shadows. It should be built with the ridge running east to west so that low angle of
the winter sun can enter along a side rather than from an end where it would be blocked
by the frame trusses. The ridge of single greenhouse should be oriented from north to
south since the angle of the sun is much higher. Ridges and furrows greenhouses at
latitudes should be oriented north to south in order to compensate for a shadow that
occurs from north roof and gutter of each adjacent greenhouse. The north-south
orientation permits this shadow to move across the floor during the day, whereas the eastwest
orientation does not.
Economy of Construction
Ridge and furrow type construction is usually more economical and needs less land
area. Some disadvantages are excessive shade from the gutters, lack of temperature
control of individual houses and no side ventilation. If forced air ventilation is used the
problem of ventilators is nullified. The greenhouses should be arranged in such a manner
so that labor is conserved and the crop can be handled more effectively. The greenhouses
should be constructed in such a way that flowers can be cut and moved to the grading
area and pot plants moved from area to area or to the shipping room very easily.
Repair and Construction Equipment
Owners of greenhouse businesses have to handle jobs like boiler repair and
operation, painting, glazing, pipe fitting, carpentry, concrete work, gas engine
maintenance, motor repair and routine maintenance of electrical and refrigeration
equipment. The larger greenhouse operation will need to have one or more individuals
who handle the engineering problems on the place.
Atmospheric Environment of Greenhouse
The atmosphere or environment in the green house affects the growth of plants. A
study of the effect of the atmospheric environment upon the plant is a study of the
response of the plant to its climatic surroundings. These factors with which the grower is
directly concerned include the air temperature, the light intensity and duration, the carbon
dioxide content of the air the relative humidity of the air, wind velocity and rainfall.
Some of the factors may be partially controlled under some conditions, but usually the
grower must alter his technique to fit the weather conditions. Any discussion of these
climatic factors implies that they all interact and therefore each one must be considered in
relation to all the others.
Air Temperature: The effect of air temperature upon plant growth must be
considered under two interrelated categories- the day temperature and the night
temperature. This distinction is well recognized by the commercial greenhouse grower. It
is universal practice to operate a greenhouse with a differential between the range of air
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