Florida Agricultural Experiment Station


radiation frost and usually occurs on still nights as a result of
the rapid loss of heat from the earth to the upper atmosphere
by radiation. By reason of the high humidity of the lower air
layers, this type of freeze is much less common in Florida than
in California. In this type of freeze the trees in groves or parts



















 Fig. 82.-Disastrous effects of the freezes of 1894-95 on citrus trees,
 showing the crop destroyed and the trees defoliated and killed
 back. From "The Cultivation of Citrus Fruits" by H. Harold
 Hume. By permission of The Macmillan Company.)
of groves in the lower situations suffer most, since the cold air,
being heavier than the warm air, flows to the lowest places. In
such cases the injury frequently is localized or spotted in groves
(Fig. 83) and the lower parts of trees are commonly injured
more than the upper parts.
 The second type of freeze is the so-called "blown-in" or "cold
wave" type, which may last from one to a few days and is usually
accompanied by considerable wind. In such a freeze a large body
of cold air is carried down over the state from the north by the
migration of a high pressure area and the conditions usually re-
sult in a very rapid radiation of heat from the soil also. Most
of the severe freezes in Florida are of this type. In such a freeze
the trees on the more exposed situations commonly suffer more
than those at lower elevations or those less protected by timber
and the upper parts of the trees often are more seriously in-
jured than the lower parts.