Horticulture Principles and Practices

FIGURE 12–37 Overhead sprinkler irrigation system.
Such a system is relatively simple to install and
operate, but results in significant leaf wetting during
irrigation. (Source: Dr. AJ Both, Bioresource Engineering,
Department of Plant Biology and Pathology, Rutgers University,
New Brunswick, NJ 08901).
180 degree nozzle
Water source
Irrigation pipe installed
around edge of bench
90 degree nozzle
FIGURE 12–38
Perimeter watering of a greenhouse bench.
in the morning to give plant foliage a chance to dry during the day. This system is used
widely for watering bedding plants.
PERIMETER WATERING The cut flower industry cannot afford to have blemishes on foliage
and flowers. The perimeter watering system is a method of greenhouse irrigation in which
water is provided without wetting the foliage of the plants (Figure 12–38). Sprinkler nozzles
are installed along the perimeter of the bench. These nozzles deliver a flat spray, and
thus the foliage and the part of the plant stem to be included in cut flowers are not wet. The
water must be sprinkled at a high enough pressure to reach plants in the center of the bench.
ISRAELI DRIP SYSTEM (FOR HANGING BASKETS) The Israeli drip system of watering
hanging baskets involves hanging plants on a support pipe at intervals that coincide
with drip points on a plastic pipe located under the support pipe (Figure 12–39).
The disadvantage of this system is that water drips on foliage, predisposing it to disease.
To minimize this problem, plants should be watered early in the morning so that they
have a long time to dry before nightfall. A modern and efficient way of watering hanging
baskets is the use of carousels (Figure 12–40).
MISTING Misting systems provide very fine sprays of water. They are used on plant
propagation benches or beds. Mists are produced from sprinklers fitted with nozzles for
very fine sprays.
POLYETHYLENE TUBING Perforated plastic pipes may be used to water cut flowers.
Pipes are laid between rows of plants in the bed.
12.3 Internal Environmental Control 431