Page 6 



blossoms are produced, on the same 

 trees, over 90 per cent of the growths 

 were of classes two and three. In 

 other words, these trees have a biennial 

 growth cycle in which the spurs fluc- 

 tuate from vegetative to fruitful. Fig. 

 1, B. The drain on the food reserve 

 for the production of blossoms and the 

 lack of a sufficient reserve seems to be 

 the factor limiting the growth of the 

 trees during the fruiting year. 



Annually bearing trees of any given 

 variety, like biennial ones, have growth 

 conditions which would account for 

 their regularity. In the first place they 

 are generally very much more vegeta- 

 tive. Their average terminal growth 

 is usually ten to fifteen inches in 

 length as compared to four to six inches 

 for off-year trees. Accompanying this 

 greater terminal growth are some very 

 important differences in blossom bud 

 production, such as the occurrence of 

 blossom buds on secondary growths 

 and the formation of some terminal and 

 lateral blossom buds. There are, how- 

 ever, two other main differences in the 

 growth of biennially and annually bear- 

 ing trees to account for their fruiting 

 differences. (1) Many non-fruiting spurs 

 during a fruiting year make enough 

 growth to become class two or class 

 three spurs (blossom forming) instead 

 of remaining class one spurs (non-blos- 

 soming), as is the case with biennial 

 trees. Thus some blossom buds are 

 formed while the tree is fruiting. (2) 

 What is probably the principal differ- 

 ence between the two types of trees is 

 in the fruiting spurs on third year 

 wood. Trees with short terminals de- 

 velop few spurs on second year wood. 

 Such as are produced are usually weak 

 and do not form blossom buds unless 

 spurs over the whole tree are forming 

 them. With trees having terminal 

 growths of a foot or more in length, on 

 the other hand, there are several spurs 

 on second year wood, some of these are 

 usually of classes two and three and 

 blossom buds are formed regardless of 

 whether the older spurs are in or out 

 of fruit. 



Before discussing control factors it is 

 well to restate that the spurs and 

 growth lengths of which we have been 

 speaking are not the cause of blossom 

 bud formation. Internal compositions 

 have been shown, as by Kraus and 

 Kraybill,* to be related to external re- 

 sponses, one of which is fruitfulness. 

 It is apparent, then, that any factor 

 causing changes in the reserve foods of 

 the plant could affect its fruiting. The 

 value of any cultural practice in giv- 

 ing fruiting is an indirect one, acting 

 through its having modified the internal 

 composition of the trees. It is prob- 

 able that less value should be placed 

 upon any single treatment as fertilizing, 

 cultivating or pruning, than has been 

 the case formerly. Different treatments 

 may have similar effects, thus pruning 

 of a certain type could have the same 

 effect upon fruitfulness as certain fer- 

 tilizer applications, through a like ef- 

 fect upon the tree composition. There 

 are, however, some rather definite ef- 



•Oregon Experiment Station Bulletin 149. 



BETTER FRUIT 



fects from the different practices and 

 it is in a few of these that we are 

 especially interested. 



Before deciding upon a cultural prac- 

 tice to remedy poor fruiting it should 

 be recognized first that lack of fruit 

 might come from either an over vege- 

 tative or an under vegetative condition 

 and that it is in an intermediated one 

 in which the greater fruitfulness oc- 

 curs. After having classified the trees 

 as to their condition, the character of 

 remedy to be used can be foretold more 

 accurately. The orchardist has rather 

 definite signs by which to measure the 

 vegetative state of the trees, as leaf sizes 

 and color, length and diameter of spurs 

 and branches, fruit sizes and colors 

 and the occurrence and position of 

 blossom buds. 



Trees with long growths, dark green 

 leaves and large, often poorly colored 

 fruits generally have a high nitrogen or 

 protein content and a low carbohydrate 

 content. The latter substances are ap- 

 parently used up in making new vegeta- 

 tive growth. The presence of nitrates 

 seems to largely determine the vegeta- 

 tive condition of the trees. With an 

 abundance of nitrates and moisture 

 there is a large growth and a conse- 

 quent lower carbohydrate content. 

 This creates conditions which have 

 been found to be unfavorable to blos- 

 som bud formation. Hence over vege- 

 tative trees are often unfruitful. Con- 

 versely, trees making little growth, hav- 

 ing yellowish green leaves and pro- 

 ducing small, unusually highly colored 

 fruits generally have a low nitrogen 

 content and a high carbohydrate con- 

 tent. The carbohydrates apparently ac- 

 cumulate because of little being used 

 up in the production of growth. Such 

 trees may be too low in vigor to pro- 

 duce blossom buds or, if they do de- 

 velop them in abundance, they are too 

 weak to produce much fruit. With this 

 in mind and knowing that fruitfulness 

 results from a condition of balance be- 

 tween the nitrogen and carbohydrate 

 content we can proceed to a considera- 

 tion of control measures with better 

 chances of making suggestions of value 

 than was possible formerly. In gen- 

 eral, nitrogenous fertilizers such as ni- 

 trate or soda, proper cultivation and 

 heavy pruning can be used to increase 

 the vegetative growth of the trees. The 

 opposite conditions, as sod culture and 

 no pruning may reduce the growth to 

 the point of poor fruiting. 



Biennially bearing trees are typically 

 low in vegetative growth. In their case 

 the question is usually one of what 

 means to employ to increase the 

 growth. This leads to the question of 

 the specific values of the different cul- 

 tural practices in inducing a condition 

 of greater vegetation. Unfortunately 

 not much is known of these values at 

 present. However, some generaliza- 

 tions based upon common experience 

 and experimental results can be made 

 with some assurance of keeping to fact. 

 Nitrogen is recognized as a raosl im- 

 portant fertilizer element in inducing 

 an increased growth. Experimental 

 trials show that the applications should 

 be made early and in a readily available 



January, 1921 



form. Two factors have a bearing 

 upon this result. One is the very low 

 nilrogen content of most soils at the 

 time of spur growth, even though they 

 have a high available nitrogen content 

 later in the season. The other is the 

 very short period of spur elongation. In 

 Wisconsin the shorter growths, which 

 are typically the fruiting spurs, make 

 their growth in length by the time the 

 trees come to full blossom. Any suc- 

 cess in increasing spur length and leaf 

 area depends naturally then upon an 

 application of fertilizer two or three 

 weeks before the trees blossom. The 

 result of the use of nitrogen fertilizers 

 is to increase the growth, especially 

 that of the terminals. From the off- 

 year standpoint fertilizers could be used 

 to maintain a terminal growth that 

 would give blossom bud formation on 

 the second year wood and fruiting in 

 the third year. 



Too little is known of the specific ef- 

 fects of cultivation in increasing tree 

 vigor. It is a common experience that 

 cultivation generally increases the 

 growth. Whether this is due more to 

 changes in moisture or in fertility con- 

 ditions is not certain. At any rate the 

 cultural treatment of any one season 

 seems to have more effect upon the 

 terminals than upon the spurs. This 

 might be expected from the relation of 

 cultivation to nitrate formation. Good 

 cultivation greatly increases the amount 

 of nitrates in the soil as compared to | 

 that in sod orchards. The important l 

 point is that the nitrogen content is notl 



Figure 2. Effect of "Small Cut" Pruning Upon 



Spur Growth. 

 Older run out spurs can he made more vege- 

 tative by making pruning cuts close to spurs. 

 Thin out top with many small cuts instead "I 

 by removing a fewer number of larger limbs. 



