Air currents are of local or regional occurrence and though not often the determinant of profitable culture of plums have sometimes been important factors in choosing a location to grow this fruit. The occurrence, direction, moisture condition and temperature are the attributes of air currents usually considered. The failure of many plums to grow in the prairie region of the Mississippi Valley and the Great Plains is no doubt due in some measure to winter winds. The problem of varietal adaptation is more or less complicated in any region by the nature of the air currents. An extremity of any of the constituents of what we call “weather” endangers the plum crop at blossoming time. In New York stresses of weather are probably the predominating causes of the non-setting of fruit on plum trees which bear an abundance of blossoms. This is well shown in a study of the relations of weather to the setting of fruit made by the New York Agricultural Experiment Station in which it is held that several phases of weather at blossoming time cause the loss of plum crops.[146] Thus late frosts, wet weather, low temperature, strong winds and wide daily ranges in temperature were factors in the loss of fruit crops in all of the failures during a period of twenty-five years. Quite as significant was the fact that in all of the years during this period when there was sunshine and warm, dry weather during blossoming time there were good crops of fruit. Locations for growing the different varieties of plums are selected with reference to general and local climate. As regards general climate, latitude, altitude and proximity to large bodies of water are the chief determining characters; as regards local climate, the lay of the land has most to do as a determinant. Again, varieties are selected with reference to time of blooming, that they may escape in some degree injurious climatal agencies. Lastly, varieties are selected having greater capacity, from one cause or another, to withstand injurious weather. With all varieties it is found that cultural treatment to induce strong vitality helps a tree to withstand stresses of harmful weather at blossoming time. The above considerations show that the blossoming dates of plums should be known for the proper culture of this fruit. In the following table averages of the blooming dates of varieties of plums for the eight years just past, 1902 to 1909, inclusive, are given.