208 GROWTH OF TREES AND FORMING OF FRUIT BUDS 



can be used as one measure of tree growth, although their 

 thickness and also the increase in the diameter of the branches, 

 spurs, and trunks should also be considered. 



(6) Determine When Length Growth Ceases. The time at 

 which length growth ceases varies with the different fruits and 

 with several other factors. Thus it is common knowledge that 

 peach trees normally continue growth in length much later in 

 the season than apples, pears, or European plums. The 

 length of the growing period for terminal shoots varies with 

 many factors such as: (1) age of tree, (2) rainfall, (3) sum- 

 mer heat, and (4) to some extent with pruning and soil fer- 

 tility. 



Vigorous, young trees normally continue terminal grow^th 

 later in the season than old trees. In seasons of abnormally 

 heavy rainfall growth may continue much later than in years 

 of normal rainfall. Trees which have been pruned heavily 

 usually grow later in the season than lightly pruned trees. 

 'Heavy applications of nitrogenous fertilizers, especially if 

 moisture is abundant, also generally cause trees to grow much 

 later than usual. 



The rate of terminal growth is very rapid early in the 

 season; it gradually slows down and finally ceases. In most 

 years, length growth is completed by the first to the fifteenth 

 of July, at least in the northeastern and central-eastern states. 



(c) Determine When Growth in Thickness Ceases, Limbs, 

 trunks, roots, and other parts increase in thickness and may 

 continue such thickening for a considerable period after length 

 growth of shoots has ceased. As long as the bark will peel 

 readily, the cambium cells (the thin layer of actively growing 

 tissue just insid.e the bark) are probably still dividing and 

 growth is continuing. Branches and roots apparently increase 

 in thickness even after the cambium cells have ceased to 

 divide. 



(d) Study and Determine the Location of Leaf Buds, 

 Fruit Buds, and Fruit Spurs. Buds on fruit trees are pro- 

 duced in the axils of the leaves on the sides of shoots and spurs 



