Page Six 



Another set of measurements presents data 

 perhaps still more interesting and instruc- 

 tive. Several hundred strongly vegetative 

 shoots of two, three and four-year-old 

 French prune and Bartlett pear trees were 

 selected and comparable branches headed 

 in such a way as to leave 12, 24 and 36 

 inches of the new growth. Table 3 sum- 

 marizes the results obtained on the prune 

 trees. Similar results were obtained from 

 the pear trees. 



These figures seem to indicate that head- 

 ing-back new growth an young non-bear- 

 ing trees reduces, in direct ratio to its 

 severity, resultant new shoot growth, stock- 

 iness and number of spurs formed. 



BETTER FRQ IT 



the Oregon Experiment Station have 

 already yielded results which emphasize 

 this statement. 



In order better to comprehend certain 

 plant responses, facts should be recalled 

 concerning the annual cycle of growth and 

 devclopement of the fruit tree. The sea- 

 son's first burst of growth — blossoms, leaves, 

 and new shoots — is made largely at the ex- 

 pense of plant food reserves, normally 

 stored in the tree during the preceeding 

 summer and fall. These stored plant re- 

 serves are thus very materially used up 

 during the early part of the summer and 

 as a consequence concentration of the cell 

 sap is lowest at this time. The crude sap 



TABLE III. 

 INFLUENCE OF SEVERITY OF PRUNING ON DEVELOPMENT OF ONE-YEAR SHOOTS 



OF FRENCH PRUNE 



Shoots of Equal Size Pruned to 



Circumference at Base 



Number of Spurs Formed — 



Length of New Shoots 



12 



inches 

 .57 inches 

 4.68 



154 inches 



24 inches 



.74 inches 

 9.43 



230 inches 



inches 

 ncehs 



36 



.9 

 1430 

 284 inches 



SUMMER pruning non-bearing trees, 

 whether performed early or late in the 

 season, exerts a marked influence on vigor 

 as measured by trunk increments. During 

 the summer of 1916 four blocks of 

 flourishing two-year-old trees consisting of 

 apricots, cherries, peaches, pears, plums 

 (Japanese and European) and prunes were 

 subjected to various treatments. 



Block A (152 trees) received no sum- 

 mer pruning, and the average increase of 

 trunks was 7.5 centimeters. Block B (252 

 trees) received a moderate thinning-out 

 and heading-back on May 4, and the aver- 

 age increase of the trunks was 6.5 centi- 

 meters. Block C (96 trees) received a 

 moderate thinning-out and heading-back on 

 May 4, and again on July 1 1, and the aver- 

 age increase of the trunks was 5.2 centi- 

 meters. Block D (30 trees) received a 

 moderate thinning-out and heading-back on 

 August 8, and the average increase of the 

 trunks was 5.4 centimeters. There were 

 only apricots, cherries and pears in this 

 block. 



From the figures just presented its seems 

 that summer pruning at any time is devital- 

 izing, and that midsummer cutting is more 

 weakening than that done during the early 

 part of the season. It is to be further noted 

 that two comparatively early summer prun- 

 ings were only a little more weakening than 

 one given late in the growing period. 



It is not the intention to give the im- 

 pression that little or no pruning of voung 

 trees is desirable, but rather that the 

 orchardist should bear in mind the observa- 

 tions herewith presented and shape his 

 pruning practices with the end in view of 

 obtaining the advantages to be derived from 

 a knowledge of the facts. 



Attention should, at this point, be drawn 

 to the fact that the same principles or 

 factors governing the growth of non-bear- 

 ing trees do not necessarily hold when bear- 

 ing trees are considered. The most excel- 

 lent pruning investigations in progress at 



taken up by the roots is transported to the 

 leaves where, with carbon dioxide from the 

 air, the complex plant foods are elaborated. 

 After the active vegetative period of 

 early summer is past the plant begins to 

 store such elaborated foods as are not 

 needed for the promotion of diameter 

 growth, nourishment of the fruit crop and 

 development of fruit buds for the succeed- 

 ing spring. As the season advances the cell 

 sap, under favorable growth conditions, 

 becomes more and more concentrated, in- 

 dicating the . storage of reserves for the 

 winter months and the following year's 

 growth. Any practice which will aid this 

 normal development of the tree should 

 materially benefit succeeding wood and 

 fruit production. 



31 arch, 1922 



TT HAS been demonstrated many times 

 -■- that heavy cutting during the dormant 

 period will result in rank succulent vegeta- 

 tive growth the following season. Un- 

 fortunately many growers have mistaken 

 these rapidly growing shoots as a sure in- 

 dication of a healthy and vigorous condi- 

 tion of the tree. Pruning, however, may 

 be so severe that the proper balance between 

 the vegetative and reproductive functions 

 are disturbed to such an extent that the 

 new growth will take practically all the 

 plant's energies to maitain and extend it 

 far beyond the proper time for the term- 

 ination of such devepoment and the begin- 

 ning of storage of synthesized plant foods. 

 Excessive pruning results in rank 

 vegetative growth near the pruning cut 

 which, with its soft, succulent, spongy tis- 

 sue, is probably wasteful in its use of soil 

 moisture and also in times of stress may 

 even withdraw water from the green fruit. 

 If soil moisture conditions are not remedied 

 shortly the tissues of the wilted, immature 

 fruit become irreparably injured. In sec- 

 tions of limited rainfall, or where irriga- 

 tion water is not plentiful, the question 

 of what type of tissue uses the greatest 

 amount of water is most important. The 

 data secured from careful experimentation 

 are meagre and seem somewhat contra- 

 dictory, but from field observations it ap- 

 pears that trees and especially vegetables 

 with very succulent growth are those which 

 suffer first from a deficiency of soil 

 moisture. 



The later the tree continues its active 

 prolongation of new wood during the sea- 

 son,, the less is the opportunity to store 

 plant food reserves and, therefore, the less 

 is the concentration of the cell sap. It 

 {Continued on ■page 23) 



Comparison of trees in background with those in foreground shows plainly how an application of miscible 



oil retards the buds in the spring. 



