Atmospherical Influences 65 
The proper treatment for trees whose shoots have been 
frost-killed, is to head them back severely to sound wood 
in order to get rid of the injured, and to supplant it by 
active, healthy growth. This pruning is best done shortly 
before the foliage starts, when the extent of the injury can 
be better noticed. ‘Trees or branches thus injured by fall 
frosts may sometimes leaf out and bloom in spring, but they 
soon succumb for lack of sufficient water-supply through 
the injured parts. 
The loss of foliage with the approach of winter, which is 
a natural physiological process, is more or less connected 
with changes in temperature conditions, and hence in some 
years may occur earlier, in others later than usual, without 
being a sign of sickness. Besides leaves, certain species, 
like Elm, Linden, Black Locust, Poplar, Willow, Oak, 
Bald Cypress, and many others shed more or less regularly 
whole branchlets, from one to ten years old, and more. 
This phenomenon may also be considered pathological, 
although it occurs quite frequently, and sometimes regu- 
larly and systematically. Neither the cause nor the rem- 
edy is known. This shedding of branchlets is entirely 
different from the loss of the tips by frost, regularly experi- 
enced by some species like Linden, Elm, and Sycamore, and 
by exotics which find the summer too short to finish their 
erowth. This habitual freezing back can be prevcnted by 
defoliating the branchlets before growth ceases, when the 
wood will harden before the frosts come. 
In other species such loss of the young twigs occurs only 
under special conditions, namely, when the young wood 
has not been matured in time. This is apt to happen when 
a late and warm moist fall follows a dry summer, inducing 
belated growth which does not harden but remains succulent 
and is nipped more or less severely by the early frosts. 
