Horticulture Principles and Practices

may be used for one pot or a group of several pots. Alternatively, a pot
may be set on a wooden block placed in a saucer and treated like the
pebble tray setup.
3. Enclosed chamber. For plants that are very sensitive to low humidity, enclosed
glass or plastic chambers or bottles may be used to hold potted plants or grow
such plants (as is done in a terrarium).
4. Move plants. Certain parts of the home have higher humidity levels than others
(e.g., bathroom and kitchen). Plants may be moved close to these humid sections
during the winter months.
Caution: Relative humidity and temperature work together. If the temperature is high,
RH will be low. On the contrary, when RH is high and the temperature in the house drops,
water will bead on the leaves. These droplets of water provide a humid environment for
maintenance of disease organisms.
11.3.8 WATER
Water plays a very important role in plant nutrition. One of the most common problems
in houseplant culture is overwatering. Plant species differ in their moisture requirements.
Several factors determine the water needs of houseplants:
1. The room condition, which varies with the season, determines how plants must
be watered. Warm or hot environments cause plants to lose more water than
cooler environments.
2. Actively growing plants use more water than dormant plants.
3. Plants with thin leaves and larger leaf surfaces transpire more and thus need more
water than other types of plants.
4. The container material plays a role in the moisture needs of plants. Plastic,
styrofoam, and glazed containers retain more moisture in the growing medium
than clay pots or unglazed containers. Plants grown in unglazed pots require
frequent watering.
5. Plant growth media differ in their water-holding capacity. Sandy soils or those
containing perlite drain more freely than those containing organic materials such
as peat. Freely draining soils require more frequent watering than those with
good water-holding capacity.
6. The size of the container in relation to plant size is also critical. When a large plant is
grown in a small pot that can hold only a small amount of water at a time, more
frequent watering is required. In addition, the roots of large plants in small pots
become pot-bound, requiring repotting of the plant.
The greatest danger of overwatering is from watering according to a set schedule.
It is safest to always determine that a plant needs water before providing it. If, a week
after watering, the soil is still reasonably moist, further watering should be delayed.
Symptoms of overwatering are wilting (in the presence of abundant moisture), yellowing
of leaves, and rotting; symptoms of lack of moisture include drooping of leaves and
wilting. Although these symptoms are stress alerts, it is best to avoid them. Plants cannot
be revived after a certain stage of wilting, especially in the case of plants with thick
leaves. Sometimes, when the plants are revived, portions of the leaves (the edges) may
be permanently scorched, leading to disfigured leaves and decreased aesthetic appeal.
Physiologically, alternating between drought and adequate moisture conditions (just like
repeated freezing and thawing of food) offsets developmental processes in the plant
including reproductive processes and may cause tissue death.
Many different types of equipment are available for measuring soil moisture.
A moisture meter may be purchased by the avid gardener. For most people, a simple
moisture indicator that changes color based on the dryness of the soil is satisfactory.
There are other ways in which soil moisture can be determined without using
11.3 Caring for Houseplants 369