222 GROWTH OF TREES AND FORMING OF FRUIT BUDS 



The four classes are as follows: 



Class L If the supply of moisture and nitrogen is abun- 

 dant, but that of carbohydrates is restricted, growth will be 

 weak, slender, and feeble, and there will be little or no pro- 

 duction of flowers. Although this condition is not common in 

 orchards, it might occur if trees were defoliated yearly by in- 

 sects, diseases, or spray material. Trees pruned heavily in the 

 summer would probably fall into this group also. 



Class II. If the supply of moisture and nitrogen is abun- 

 dant, and there are sufficient carbohydrates to utilize this nitro- 

 gen supply, a strong, vigorous wood and leaf growth results, 

 but still very few fruit buds are formed. The carbohydrates 

 are used in growth, leaving no surplus for fruit-bud formation. 

 This condition is well illustrated by vigorous, rather heavily 

 pruned young orchards, which continue to grow vigorously, on 

 rich, moist, fertile, cultivated soils, but do not come into 

 bearing. 



Bearing apple trees which have been too heavily pruned and 

 headed back in the dormant season usually fall into this class 

 for two or three years after the pruning. The carbohydrates 

 stored in the limbs, spurs, etc., are cut away in the pruning, 

 resulting in an unusually large supply of nitrogen and water 

 for those buds which remain. The removal of so many buds 

 also reduces greatly the amount of growth and leaves which 

 normally would have been produced. Thus, less carbohy- 

 drates would be made and stored. 



Class III. If the moisture and nitrogen supply is ample, 

 and there is an excess of carbohydrates over and above the 

 amounts utilized with the nitrogen, there is not only a good 

 growth of tree, but also an abundant supply of fruit buds. 

 This is the condition found in healthy, producing orchards. 



Class IV. If there is a deficiency of nitrogen and an abun- 

 dance of carbohydrates, an extremely weak growth, yellowish 

 foliage, with either few flowers produced or else a production 

 of flowers too weak to set fruit results. This is the condition 

 usually found in so-called '^starved^' or "devitalized orchards." 



