A damage survey including 59 fields at the Range Cattle
Station following the 1957-58 winter is summarized in Figure 7.
This was the first injury over an extensive area recorded in
south Florida. It can be seen that in spite of severe losses, more
than half the pastures had in excess of 20% survival. These
were returned to grazing by June 1, and even the most severely
damaged areas were in use by July 1, after fertilization and
favorable moisture conditions. There was no consistent relation-
ship between fertilizer rate and stand loss observed in 1958 ex-
cept on several small pastures which received 300 pounds N per
acre annually and suffered more winter damage than ones
treated at lower rates.
 Levels of fertilization above 200 pounds N per acre annually
should be avoided where winterkilling of pangolagrass is an
important factor. Control of N fertilization holds little promise
for cold damage reduction in the main pangolagrass-growing
areas of the state since few pastures receive more than 200
pounds N per acre. Added to this is the fact that winterkilling
in unfavorable years shows limited relationship to N fertilization
below this level. It is doubtful that a build-up of plant health
and vigor can be used to increase the winter hardiness of pango-
lagrass sod. Lack of dormancy is associated with the problem,
and any condition which encourages cool season growth increases
susceptibility to cold damage.

Rainfall
 The winterkilling noted in 1958 occurred during a high rain-
fall period which was thought to be at least partially responsible
for the damage (13). Subsequent mortality observations made
in the spring periods of 1962, 1963, and 1964, following normal
to dry winters, showed that excess moisture is, at most, a minor
factor in winterkilling.

Ground Cover
 Effect of amount of ground cover on extent of cold damage
is variable, but evidence shows that damage is increased by the
presence of large amounts of mature or dead grass, particularly
under heavy N fertilization (30). This gives rise to the descrip-
tion of winterkilling as "smothering". Tall grass protects
underlying leaves and stems from light frost damage but is not
effective against severe cold temperatures. Trials with Coastal
bermudagrass in Gainesville in December 1962 indicated that
minimum temperatures in 12-inch grass did not fall as low as in