11 



sequel! lly low temperature will not have such an m- 

 jurious ell'ect, unless two or three weeks of warm 

 weather has prevailed followed hy a drop in tempera- 

 ture. 



Under no consideration should an orchard be lo- 

 cated where a small water course, pond or swamp 

 is found in the immediate proximity on the north-east, 

 north or north-west sides because the cold air that is 

 formed in these places under low temperature, instead 

 of being dispersed by the wind will lodge over the sur- 

 face of the ground in the orchard and cause severe in- 

 jury to the trees, and if they are not entirely dormant 

 it will kill them. This applies also where the water 

 course is located on the south side and where the slope 

 is rather long and steep. The wind will disperse the 

 cold air from the surface of the ground on the north- 

 ern part of the slope, but wall not do so on the south- 

 ern part and consequently the trees growing on the low- 

 er south side of such slope will suffer from the cold 

 damp air coming off the water course, pond or swamp. 

 It must be remembered that it is not the cold wind that 

 kills the tree, but the cold, damp air that creeps over 

 the surface of the ground and settles. See graph-maps 

 pages 7 and 8. 



The future planter of an orange grove should bear 

 the foregoing in mind and select the site for his orch- 

 ard so that he has as perfect air drainage as possible; 

 that the composition of the soil is not too light; that the 

 slope towards the south is moderate; not over one 

 inch per foot if there is high land across the valley. 

 If the foregoing is followed there will be less frost dam- 

 age in the future than in the past. 



The reason for the greater part of the damage sus- 

 tained in November, 1916, and February and March, 

 1917, was in each case due to the fact that prior to such 

 low temperature the weather was warm and the trees 

 had begun to grow. The sudden drop of temperature 

 under conditions described in graphs on pages 7 and 8 

 w^as mainly responsible. If the trees had been dor- 

 mant prior to the low temperature, there would have 

 been no damage. 



On the 15th of November, 1916, the tcmi)erature was 

 high, the thermometer registering about 80 degrees 

 above zero; on the morning of the 16tli the tempera- 

 ture had dropped down to 27 degrees above zero. This 

 sudden drop was responsible for the serious losses sus- 

 tained at that time, both to the small as well as to the 

 larger trees. 



