70 FUNDAMENTALS OF FRUIT PRODUCTION 



below normal. ... It is evident from the precipitation figures for 1913 that 

 the pines in that year depended entirely upon winter precipitation for their height 

 growth. Since the total precipitation in April, May, and June was only 0.25 

 inch, it may be readily seen that an addition of 2 or 3 inches during this period 

 would have resulted in an appreciable increase in soil moisture and presumably 

 in height growth. Such was the case in 1914 and in a more marked degree in 1915 

 and 1917. If, as is often the case, the first of April marks the end of the season's 

 storms, a dry period of 3 months prior to the beginning of the summer rains may 

 be expected. Since yellow pine, on account of the low temperature, does not 

 begin growth until about the middle of May, a dry period of 6 weeks intervenes 

 between the last storm or the disappearance of snow and the beginning of growth. 

 During this period a large portion of the stored moisture supply is dissipated 

 without benefit to the tree. If, on the other hand, belated storms continue 

 through April and into May, the stored water supply is not only conserved, but 

 may be actually augmented. A typical example of the first type of spring was in 

 1916. Despite a winter precipitation of over 16 inches, the highest on record in 

 9 years, soil moisture conditions, after it became warm enough for growth, were 

 decidedly below normal. . . . The years 1915 and 1917 are examples of the 

 second type of spring. The winter precipitation was only 9.4 inches in 1914-15 

 and 6.1 inches in 1916-17, but in both years the precipitation between April 

 1 and May 15 was around 6 inches." 



The '^Second Growth" of Midsummer or Late Summer. — A second 

 period of rapid vegetative growth frequently occurs in late summer or 

 fall. Usually it takes place after terminal bud formation on both spurs 

 and shoots in the case of spur bearing species. Sometimes the terminal 

 buds on the shoots "break" and a new shoot growth is pushed out; 

 sometimes terminal buds on many of the spurs "break" and a secondary 

 spur growth takes place and sometimes the lateral buds, rather than 

 the terminals, initiate this new shoot growth. In some instances terminal 

 bud formation has not yet occurred in the primary shoots of the season, 

 though growth has slowed down very materially, so there is a sudden 

 flush of rapid vegetative development. Occasionally this "second 

 growth," as it is generally called, is as extensive in amount as that made 

 early in the season, though this is not usually the case. Without doubt 

 nutritive conditions within the plant and in the soil have something to 

 do in determining "second growth" but the fact that it occurs almost 

 invariably after heavy rains or irrigation following a drought, leads to 

 the conclusion that it is due at least in part to changed moisture con- 

 ditions. It is to be regarded as a phenomenon likely to accompany irregu- 

 larity in moisture supply late in the season, and is a response of the 

 plant to disturbed moisture relations. This second growth is sometimes 

 accompanied by fall blooming in some of the tree fruits. Without 

 doubt the "flush" of certain evergreen plants of tropical countries is 

 a related phenomenon. It sometimes gives rise to two "annual" rings 

 in one season in the trunks and limbs of trees and other woody plants. 



