Symptoms and damage
Many of the more showy
and exotic succulents originated in frost-free climates. As a result, when
temperatures remain below freezing for several hours, they suffer freeze
damage. The damage originally manifests itself as blackening of the exposed
parts of the plant .After
a few weeks, the blackened area will dry out
and become crisp.
When exposed to a severe freeze, portions of
columnar cacti will yellow, and then die completely .In
freeze-damaged barrel-type cactus, the margins of ribs become
straw yellow. If temperatures are not
substantially below freezing (a “hard freeze”) and the freeze lasts for only a
few hours or less
Freeze damage can be prevented. It is important
to become acquainted with temperature requirements of the particular species.
Protective measures often can be taken to assure survival. Cold-sensitive
plants should be grown in areas that receive radiated heat at night from a
patio or wall or in hilly areas where air temperatures are slightly warmer.
Covering the plant with a cotton sheet will
help on nights that are just at or slightly below freezing. Another strategy is
to place a 60-watt light bulb under the cotton sheet, taking care that the
light bulb does not touch the plant or the cotton sheet. Do not cover the plant
with plastic sheeting. Plastic is a poor insulator and will transfer the cold
directly to the plant wherever it touches the plant. Containerized plants can
be moved indoors until freezing weather has passed. If kept dry and placed in a
brightly lighted area, they will survive without damage.