April, ig20 



BETTER FRUIT 



Page 



bloom, especially where the enforced 

 dormant season of winter is very long. 

 The blossoms, on the other hand, are 

 very tender. There is a great range in 

 the degree of frost which will cause 

 injury, depending largely on the condi- 

 tion of the tree during the time that the 

 fruit buds are forming and developing, 

 as well as on the duration and severity 

 of the frost. Buds and blossoms on trees 

 which have been forced into premature 

 dormancy, either by lack of moisture or 

 by severe attacks of red spider, arc 

 much more susceptible to frost than 

 those on trees which have continued 

 growth late enough in the fall to pro- 

 vide for the proper development and 

 maturity of the buds. After differentia- 

 tion of fruit buds commences in the 

 summer, the almond leaves should re- 

 main on the tree until late into the fall 

 in order to strengthen and develop the 

 fruit buds and store up the elaborated 

 food material for the use of the buds 

 in their normal development through 

 the winter. Studies of almond buds 

 gathered from healthy trees which held 

 their leaves until late fall frosts at 

 Davis, showed the first evidence of dif- 

 ferentiation between fruit and flower 

 buds commencing about August 18, 

 while the flower was not completely 

 developed until February 18 following. 

 During the intervening time develop- 

 ment proceeded unchecked through the 

 winter even though the tree was ap- 

 parently dormant. During the time the 

 crop is ripening on the trees, little is 

 done toward storing food material for 

 the buds. If the leaves turn yellow or 

 drop soon after harvest, the trees do 

 not have the opportunity of storing a 

 sufficient supply of plant food for their 

 normal requirements and the buds are 

 insufTiciently nourished during the 

 winter period. The resulting buds are 

 weakened and the indications are that 

 they are unable to endure unfavorable 

 climatic conditions in the spring, such 

 as light frosts, continued cold weather 



Courtesy College of Agriculture, Berkeley, California 

 Illuslration showing some of the almond varieties grown in California. 



or sudden changes from warm to cold 

 weather. 



The most tender stage in the blossom- 

 ing and development of the young fruit 

 seems to be immediately following the 

 dropping of the calyx lobes from the 

 young fruit as it first commences to 

 swell rapidly. The blossom becomes 

 more and more tender as it opens out 

 and reaches the above stage. After the 

 young fruit has attained the size of a 

 pea it rapidly becomes more resistant 

 to low temperatures. Blossoms with 

 the petals exposed but not yet opened 

 have been known to stand temperatures 

 of 24 degrees F. and blossoms with 

 petals beginning to fall have stood 28 

 degrees F. No records are available 

 as to the duration of these temperatures. 



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 Harvcslii)^ nlmnnds by knockjnt^ 



olU'ye of Agriculture, Berkeley, California 

 onto sheds spreml on the ground. 



In other cases, blossoms with the petals 

 falling have been killed by tempera- 

 tures of 30 and 31 degrees F. It must 

 be remembered in this connection that 

 the almond blooms earlier than other 

 orchard fruits and, therefore, is often 

 subjected to much more severe frosts 

 than occur during the blooming period 

 of the later fruits. The greatest injury 

 is likely to occur when a frost follows 

 one or more days of warm weather. 

 When the mean temperature both day 

 and night remains low, frosts that 

 might otherwise kill the flowers or set- 

 ting fruit do no harm. This is what 

 occurred in February, 1917, at the Uni- 

 versity farm, when repeated frosts at 

 blooming time did not harm whatever. 

 In determining the desirability of a 

 location in regard to its freedom from 

 frost, the possibility of adequate air 

 drainage is an important item. For 

 this reason the lands along the lower 

 foothills immediately above the floor of 

 the valleys are ordinarily much less 

 subject to frost — because the cold air 

 is free to drain away to the lower levels. 

 Generally the lands along the banks of 

 streams which have been built up high- 

 er than the other lands of the Great 

 Valleys through which they flow, are 

 less subject to frost by reason of the 

 natural flow of the cold air from them 

 to the lower lands adjacent. For the 

 same reason the planting of almonds in 

 the lower lands of the valleys, no mat- 

 ter how large the valleys may be, 

 should be avoided, unless the locality 

 has been thoroughly tested for a long 

 period of years and has proved to be 

 an exception to the rule because of 

 some peculiar situation with favoring 

 air currents or air drainage, such as 

 might exist near a natural draw in the 

 hills where the settling of the cold air 

 in some portions of the adjacent valley 

 might be prevented. Such locations are 

 generally confined to very small areas. 

 Oftentimes an opening or draw in the 

 hills may serve as an outlet for the 



