White Bluffs spokesman. [volume] (White Bluffs, Wash.) 1907-1938, 1935-03-28


It must be admitted that these
data are unsatisfactory because they
do not go into sufficient detail.
The three stages of development
given are not sufficient to cover
all the changes in susceptibility
to damage which are found during the
period of development of a fruit bud
through the blossom stages to the small
green fruit. Detailed information to
supply the deficiency is not available
except in the case of apples and pears.
These data on critical temperatures on
apples and pears are given in Tables
2 and 8.
These critical temperatures are based
on field observations by the U. S. Wea-
ther bureau over long period of years.
Most of the work on apples was done
by the writer in the orchards Of North
Central Washington, in cooperation
with the state horticultural depart
ment. The work on pears was done
mostly by F. D. Young in the Rogue
River valley. The temperatures given
are considered safe as a basis for rec
concentrations for successful orchard
heating operations. Some fuel will be
wasted in maintaining temperatures
according to these recommendations
but the grower who has orchard heat
ing equipment cannot afford to take
chances. All temperatures mentioned
are sheltered-th ermometer readings. A
sheltered thermometer is one which is
exposed in the orchard with board
screen over the top to cut off free RAJ
diation to the sky. The temperature
given by such thermometer is the
temperature of the free air which sur
rounds the buds and blossoms.
Additional information on cherries
and other fruits:
The most dangerous stage in general
comes after the petals have fallen and
the fruit has set. All of the fruit is
then in nearly the same condition, and
the entire crop may be killed in
single night. It is at this time that
orchard heating operations should be
most carefully conducted Apples and
pears at this stage of development
/ usually are not seriously injured by a
temperature of 285 deg. F. for 80 min
utes or less, provided the duration Of
temperature below 80 deg. F. does not
exceed two hours. If the temperature
drops to % deg. F. at sunrise, and has
not been below 80 deg. F. more than
two hours, heating is unnecessary.
However, if it appears that the lowest
temperature during the night will be
below 90 deg. F., or if the tempera~
ture falls below 80 deg. F. more than
two hours before sunrise, heaters
should be lighted and the tempera-
ture maintained as near 81 deg. F. as
possible throughout the remainder of
the night.
ApricOts Extremely Tender
Small, green apricots are extremely
tender just after the shucks (dried
1 calices) have dropped and before the
pits have hardened. Apricots in this
stage of development have been in
] jured at long-continued temperatures
of 81 deg. F., and many growers be-
lieve it necessary not to allow the tenn
peratures to fall below 80 deg. F. as
long as the pits are soft.
From what little data are available
italian prunes appear to be exception
ally hardy before the fruit has set
In eastern Washington when pruneS
were generally showing color but none
were in full bloom, they sustained
practically no damage following
frosty night with temperature below
30 deg. F. for seven consecutive hours
with the lowest temperature % deg
F. Only scattered blossoms were dam.
aged. Later in the same year, wher
the trees were estimated to be 85 PEI
cent In full bloom, temperatures be-
low 80 deg. F. for more than 10 con
secutive hours, with the lowest tenn
perature 1877 deg. F., killed only abou
10 per cent OF the blossoms. Practical.
all the blossoms not open at the tim
of the frost escaped injury. The prun
crop harvested in the fall was abou
rs per cent of normal.
With the crop in the small green
fruit stage a temperature below 3
deg. F. slightly more than five hours
with the lowest temperature 26 deg. F
caused loss of approximately Is pc
cent of the fruit on the trees.
Few. data are available regarding
temperatures which will damage cher
ries Bing cherries about one-third Il
full bloom suffered about 33 per cen
damage on frosty night with tn
temperature below 80 deg. F. for 81
and one-half consecutive hours an
the lowest temperature 243 deg. I