i8 The Coeorado Experiment Station. 
out new leaves which will take the place of the injured ones 
Prevention of Frost Injuries in General. —As this is a subj< 
that would require a bulletin to be satisfactorily handled, we v 
give only some of the most important features concerning orcha 
heating. The following conclusions were drawn after consulti 
over forty of the leading orchardists of the State who had us, 
orchard heaters: 
1. The fact that every orchardist, who had been interview I 
upon this subject, claimed that the orchard heater is a good inve- 
ment as an assurance in the fighting of frost, indicates that t: 
orchard heater has come to stay. 
2. The oil heater is usually preferred over the coal, whi 
more than five acres are to be heated, because of its more econo • 
ical maintenance. 
3. On cold, windy nights orchards with low headed trei 
receive more benefit from the heaters than high headed ones. 
4. Good thermometers well tested should be in the orcha I 
as well as on the outside. 
5. Careful study of the stage of growth of the fruit bn; 
should be made to ascertain their hardihood against frost iniuri. 
In regard to the stage of growth of the fruit buds, bloom al 
set fruit of peaches and apples, as compared to their resistance > 
frost, the following opinions are given: Prof. W. L. Howal 
*states that in Missouri fully dormant peach buds can stand 8 : 
o degrees below zero. When appreciably swollen, zero is the da- 
ger point. When the buds are showing the pink, they can stand 5 
degrees above zero. W hen the petals are off they stand 30 degres 
above zero. For apples, when the petals begin to show, they ci 
possibly stand a temperature of from 20 to 22 degrees above zei. 
From this stage on their resistance to cold becomes less and less 5 
growth progresses. 
Prof. P. J. O’Gara fstates that, in the Pacific Northwe, 
peaches in bud are injured by a temperature of 29 degrees F.; 1 
blossom bv 30 degrees, and set fruit by 30 degree F. Apples 1 
bud are injured by a temperature of 27 degrees; in blossom by 2, 
and set fruit by 30 degrees F. 
Prof. O. B. Whipple {found that it is doubtful if, in Colorad, 
a temperature of 30 degrees F.' will injure fruit or buds, in ar 
stage of growth. That a temperature of 28 degrees, if of lot 
enough duration to freeze the tissues solid, will kill peaches 1 
* Reprint from the Annual Report of the Missouri State Board 
Horticulture, 1909. 
tParmers’ Bulletin No. 4 01, U. S. Dept. Agr. 
JFruit Growing in Arid Regions, by Paddock and Whipple, p. 3c- 
The MacMillan Company. 
