White Bluffs spokesman. [volume] (White Bluffs, Wash.) 1907-1938, 1926-03-26
INJURIOUS TEMPERATURES
By Albert w. Cook, Assistant OBJ

INJURIOUS TEMPERATURES
By Albert w. Cook, Assistant OBJ
server, U. S. Weather Bureau.
Efficient orchard heating demands
an economical use of labor and fuel
and requires a knowledge of the
temperatures that cause injury to the
buds or blossoms. Growers frequent
ly light the heaters too soon, in or
der to maintain margin of safety,
resulting in needless burning of oil
or briquettes. On the other hand,
some of the less cautious growers
wait until the critical temperature is
reached before lighting the heaters
and. as result, often suffer some
loss of fruit.
From reading of the popular lit
erature on the subject one would be
lead to infer that the buds have
definite critical temperature and when
this temperature is reached they all
freeze. This is wide of the truth.
There is range of several degrees
between the highest temperature that
will kill or 4 of the buds and the
temperature that will kill all OF them.
1t should be remembered that on the
same branch are buds that have swol-
len but slightly while others are in
full bloom. There is also a great dit
ference in the hardness of the indivi-
dual buds. "A freeze or two in the
spring may not materially reduce the
crop for there are many times more
buds on the trees than actually ma
ture into fruit. However, the buds
killed by the first freeze in the spring
are the ones most advanced because
as the buds mature they become
more susceptible to frost. The killing
Of the early buds would retard the
maturing of the fruit few days as
the later buds would probably be
naturally thinned if the early buds
had not been killed. Fruit from late
bloom is usually understood and OF
poor quality. It is very rare that a
tree has so many buds that it can not
lose half of them and yet mature an
average crop in the fall. This frost
thinning is undesirable because it
is not uniformly done. One part of
the tree may bear no fruit while an
other part may be heavily loaded and
thinning will be necessary.
In the process Of natural thinning
the number of fruits on the trees is
steadily and rapidly reduced after the
period of full bloom and the loss OF
large percentage of the fruit re-
tanned on the tree at this time is like
ly to reduce seriously the size Of the
crop harvested.
The stage of advancement is Of
the greatest Importance in estimating
resistance to low temperature; the
same degree Of frost that causes little
or no damage to fruit in the bud
may injure the greater portion of the
crop two or three days, or IA week
later. In the case of most deciduous
fruits, the same temperature will
cause far more permanent damage
after the fruit has set than. during the
period when the trees are in full
bloom, and the later the frost after
the fruit has set the greater the &C
tual loss. One or two injured bios
SONS in each cluster are usually SUI
ficient fer good crop. With
cherries a larger percentage OF the
blossoms must mature in order to OBJ
tain full crop land damage during
full bloom is more serious.
However, until some physical
measurement of the hardness Of fruit
buds is worked out temperatures
which buds will endure without being
killed can not be given definitely mol
can loss of fruit from spring freezes
be accurately determined.
West and Edlefsen, of the Utah
Experiment Station, have arrived al
the following conclusions LITTER freez
ing over $4,000 apple, peach, apricot
and cherry buds:
~, alberta peach buds in full
bloom 2o degrees safe temperature
28 degrees kills Ia to IL, 26 degrees
kills 1-2, % degrees kills 9-10, 18 de
grees has failed to kill all.
| (2), Sweet cherries in full bloom
80 degrees is safe temperature. 2!
degrees kills one fifth, rs degree
kills IL. When just showing colo
20 degrees killed 40 per cent.
(3), Injury is per cent to 10 pc
cent greater when fruit is setting thai
when in full bloom with same mini
mum temperatures.
| (4), Sour cherries are the hardest
then apples, peaches, apricots, an
sweet cherries.
Different varieties of the sam
fruit often differ considerably in de
gree of resistance to frost danag
and when the same critical tempera
ture is given for all varieties, it
applicable only In very genera
way. The following table of critica
temperatures as recorded by a Pre-
perly sheltered thermometer in the or.
chard is meant to give a general ide
of what the blossoms will endure 70
one half hour or less without injury
Fruit Closed but Full After frui
showing color bloom has SCI
Apples .........- Is % 20
Peaches ...-..... Is rs 20
Cherries 49,. rs 20 80
Pears ............ Is 28 80
Apricots ...... rs Fl 80
Prunes mecca. % 20 80
The best possible arrangement t
be followed by the orchardist VIII
protects his orchard is to first deter
, mine the temperature the buds wi
, stand, based on stage Of developmer
ETC.. allow a certain amount as