112 PROCEEDINGS OF TWENTY-SIXTH FRUIT-GROWERS- CONVENTION. 



California as frosts. Notwithstanding statements sometimes published, 

 that certain areas are in the so-called frostless belt, there does not 

 appear good reason for believing that any portion of the State may not 

 be visited by frost. 



The losses to the fruit crop, both citrus and deciduous, through frost, 

 have been so large that special attention has been given to methods of 

 protecting orchards; and these methods are discussed in detail in the 

 following pages. With citrus fruits the frosts of December, January, 

 and February are to be guarded against; the fruit being ripe and ready 

 for shipment. With deciduous fruits the late spring frosts do the 

 damage. Almonds, apricots, grapes, peaches, and prunes are hurt 

 while in bud or while the fruit is just setting, by the frosts of March 

 and April. The damage depends in all probability as much upon the 

 condition of the tree as upon the degree and duration of the cold. For 

 example, a sharp frost during the first or second week of April some- 

 times does less damage if the trees are fairly past the blossoming 

 period than the same frosts would have caused occurring about the 

 middle of March. 



Attention is invited to the excellent table prepared by Mr. Samuel 

 H. Gerrish of Sacramento, giving the dates of first and last light and 

 killing frosts; also the dates of blooming fruit trees in Sacramento, 

 from 1869 to 1901. 



The protection of gardens, both vegetable and flower, is also impor- 

 tant. The particular frosts affecting gardens are the frosts of February, 

 March, and April, and it is pointed out in the succeeding pages that the 

 same general principles used to protect orchards should be followed in 

 the protection of gardens. A clear, still night, following thirty-six or 

 forty-eight hours of boisterous north wind, is likely to be followed by 

 frost, particularly if the movement of the air in the given locality has 

 been such as to cause a settling of cold, relatively dry air strata in the 

 hollows or depressions of the land. The formation of frost is essentially 

 a problem in air drainage, and if by any means we can prevent 

 streaks, pools, or basins of stagnant, cold dry air, we can largely prevent 

 frost. Frost, as commonly understood, is the water vapor of the air 

 deposited upon the plant at a temperature below 32°. The damage to 

 plant life is, however, really caused by the falling or rising temperature, 

 and not by the deposit of ice. The water vapor plays the part of an 

 index only. Indeed, the action of the water is preventive. Dry air at 

 a temperature of 32° weighs 563 grains per cubic foot. Water vapor at 

 32° weighs 2.1 grains per cubic foot at a saturation of 100 per cent. 

 Air at a temperature of 25° F. weighs 572 grains per cubic foot. Given 

 a little time, therefore, on a still, clear night, the loss of heat by radia- 

 tion from the plant surfaces and the ground will bring about a settling 

 of the colder air to the bottom. The ground will be covered with frost. 



