When plants are under-fertilized more
nutrient can be added, no harm done.
Overfertilization can kill a plant quickly.
Growers take no chances when they
change hydroponic nutrient water solutions
every 2 weeks. Even though the solution
may have nutrients left, it is probably
unbalanced since the plants have used
some of the nutrients, and not others.

Chapter 15

AIR AND

TEMPERATURE

Temperature, movement, humidity and
content of the air all affect plant growth.
Unlike warm-blooded animals, which
can function regardless of the outside
temperature, plants’ rate of metabolism,
how fast they function and grow is
controlled by the temperature of the
surrounding air.
At low temperatures, under 65 degrees,
the photosynthesis rate and growth are
slowed. The difference in growth rate is not
readily apparent if the temperature dips
once in a while or the low temperatures are
not extreme. However, temperatures under
50-55 degrees virtually stop growth.
Temperatures in the 40’s cause slight
temporary tissue damage. When
temperatures dip into the high thirties tissue
damage which takes several days to repair
may result, especially in older plants.