FROST DAMAGE TO ORCHARDS 



against frost, and this often is a most practicable method. 

 One quart of water evaporated into the air, in a space eighty 

 feet square will protect against frost as much as raising the 

 temperature ten degrees. 



A slope which faces the water usually is better than one 

 exposed the other way. The prevailing strong winds, however, 

 have something to do with this, as well as sun and soil. South 

 and west slopes are not so good as others, except for quinces 

 and grapes, so far as the frost problem is concerned. A body 

 of water will influence the temperature to a useful extent up 

 to a distance of from five to fifteen miles. No difficulty will 

 be had in getting local information on this point, and one 

 season's acquaintance with conditions will tell the story pretty 

 well. 



As the entire country from Ontario south is adapted to some 

 or all of the fruits, there are ten times as many inland acres 

 as there are of those under the protection of bodies of water. 

 Over all this area other things must be relied on to control 

 frost trouble. The first of these is air drainage next to right 

 varieties, moisture, fertility and pruning, the most important 

 requisite for success with fruit. 



The greatest danger to blossoms from frost comes during 

 still nights. Frosts seldom come when a wind blows, because, 

 when it is in motion, all the air is mixed together and its tem- 

 perature is uniform throughout. After there has been enough 

 spring warmth to produce bloom, nearly always enough will 

 be stored up in that neighborhood to keep the temperature 

 of all the atmosphere above the danger point if it is distributed 

 properly by air movement or wind. Air-drainage is air-move- 

 ment by gravity when the wind is not blowing. 



Air-drainage, and freezing at blossom-time, depend on 

 comparative height, not on distance above sea-level. It does not 

 take much slope or drop to do the work, although several hun- 

 dred feet will do no harm. Often a rise of ten feet will mark 

 the line between frost and safety, and places with a difference 

 of ten feet in elevation sometimes will show a difference of 

 ten degrees in temperature. 



Warm air rises, just as steam does. Cold air sinks, just as 

 water runs down hill. Every little obstruction, like a few feet 

 of roll in the surface, a hedge or windbreak, even the dirt 

 thrown out of a ditch, will cause a deflection in the downward 

 flow of cold air, and may protect or doom the plants in an area 

 alongside of it. The shoulder of a hill, a hollow or a valley 

 will direct air-currents. 



When it strikes an obstruction in its flow, air bounds quite 

 a distance away from the earth, and does not come down again 

 for rods. The flow of air to the sides is deflected in the same 

 manner. We can only hint here at the influences of various 

 combinations of hills, bluffs, draws, woods, drops and land- 

 angles. No rules can be given for this. By studying the situ- 

 ation you nearly always can tell where the flows of cold air 

 will be. When the sun goes down, the earth and air cool rapidly. 

 If it is a still night, the natural or gravity movement of the 



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