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if one thorough application is made to the trees before the buds open. 



Winter and Spring Frost May Injure the Blossoms. The un- 

 fruitfulness arising from winter or spring frost injury is sometimes 

 confused with self-sterility. A common form of injury is that in 

 which the pistil is blackened and stunted, having made no percepti- 

 ble growth during the opening of the flower. These pistils always 

 drop from the tree soon after the petals have fallen. Another and 

 not less common form of injury is that in which the pistil has made 

 a partial growth but has no well developed ovary. Unless a careful 

 examination is made, blossoms like this would not be considered as 

 winter-injured. The killing of the pistils is the most common form 

 of winter injury to fruit buds. 



The injury to fruit blossoms from cold is of all degrees. During 

 the opening of a normal flower, the pistil grows. It is often taken 

 for granted that if this growth occurs the pistil is uninjured ; but it 

 may be that even though a pistil reaches its full size, it may yet be so 

 injured that it cannot develop into fruit. Some of the imperfect 

 development of flowers which is attributed to winter injury may be 

 caused by unfavorable conditions during the previous season, when 

 the buds were being formed; yet it is likely that winter injury to 

 pistils is more common and more serious than appears at first sight. 



Rain May Injure Fruit Blossoms. The unfruitfulness which 

 often follows a rain during the blooming season is sometimes con- 

 fused with self-sterility. A careful fruit-grower watches the weather 

 anxiously when his trees are in blossom, for he knows this is the 

 most critical period in the growth of the crop. Injury to fruit blos- 

 soms from rain is common wherever fruit is grown, but is particularly 

 serious along the Pacific Coast and near the shores of the Great 

 Lakes. It has been estimated that more fruit is lost in California 

 from cold rains during blooming time than from all other causes com- 

 bined. Like winter injury to fruit buds, there is no way of preventing 

 this loss except to secure a more favorable location, since it is not in 

 man's power to prevent rain. 



If a rain comes while the trees are in full bloom the pollen is 

 washed from those anthers which have already opened, and is thus 

 prevented from reaching the stigma. Should the rain be a short one, 

 no serious harm need result from this loss of pollen, for the unopened 

 anthers will burst and pollination will begin again soon after the 

 sun comes out. The washing away of pollen has very little influence 

 in decreasing the setting of fruit, particularly when the rain is short. 

 There will generally be enough pollen to supply the pistils before or 

 after the ram. 



The poor setting of fruit which often follows a long rain and 

 sometimes a shower is due more to a loss of vitality in the pollen or 

 to some mechanical injury to the pistils; also, in large measure, to 

 the fact that bees and other insects which promote the beneficial cross- 

 pollination between varieties are absent. If the rain lasts for several 

 days, the pollen may lose its vitality. It is also natural to suppose that 

 a hard rain may wash off, dilute, or otherwise injure the juices of 

 the stigma so that the pollen cannot germinate after it falls upon the 



