for January, 1920 



399 



Why Fruit Trees Do Not Bear 



ONE of the most trying and disapponiting experi- 

 ences for a fruit grower, is to have his orchard 

 reach an age when he expects a crop, only to find 

 that it does not produce. As chief of the division of 

 horticulture at the Oregon Agricuhural College one of 

 the most common letters that I received from growers 

 was, "^Vhy don't my trees bear?" 



To answer this question, we can to advantage, divide 

 the trees into two classes. First, trees which do not 

 bloom; second, trees which bloom but do not set fruit. 

 The first class is influenced by many factors, such as var- 

 iety and vigor. Many a grower has expected trees to 

 bear at an age when they naturally could not be expected 

 to bear. Some varieties will begin bearing at five years 

 of age. But on the other hand, some varieties will not 

 bear crops until they are seven years of age, and in some 

 cases much older. 



I have known Northern Spy and Yellow Newtown or- 

 chards to be unproductive until they were twelve to fif- 

 teen years of age, but under such circumstances, I might 

 add, wrong orchard practices had frequently been re- 

 sorted to. The vigor of the tree determines the produc- 

 tion of blossoms. 



The heavy pruning and intensive tillage • desirable for 

 trees from one to five years of age, is undesirable for a 

 tree from five to ten years of age, and if the practices are 

 continued may keep some varieties of fruit from bearing 

 crops until they are fifteen years of age. With trees from 

 five to ten years of age in normal vigor, less tillage and 

 irrigation, not very much cutting back but more of a thin- 

 ning out process in the pruning, will encourage trees to 

 come into bearing. 



It is to the second group of trees, namely those which 

 bloom but do not set fruit, that we need perhaps to give 

 the greatest attention. For though one may be disap- 

 pointed if trees do not bloom, the disappointment becomes 

 even greater if the trees bloom, yet fail to produce. 



There are many factors to be considered in answering 

 the question why some trees will bloom and yet fail to 

 l)roduce fruit. The climate is one of the greatest fac- 

 tors for us to consider, and Jack Frost takes an annual 

 toll from many trees. Not perhaps so much the actual 

 freezing of the tissues, but the rapid thawing of frozen 

 tissues is responsible for the huge loss in the early 

 spring. Where orchards are not exposed to the direct 

 sunlight early in the morning, or where a bank of fog or 

 cloud drives in, we often notice that the damage is little 

 or nothing. 



There is a relation between the vigor of the trees and 

 the amount of frost damage experienced. Between the 

 condition of vegetation and effect of low temperatures. 



The degree of development of the vegetation in the 

 spring at time of frost, and its relation to resulting dam- 

 age is a very interesting one. For a number of years, I 

 have observed that trees which are just starting to grow. 

 or trees which have reached the blooming or setting pe- 

 riod suffered less from frost damage than trees which 

 are half way between in their development. 



LTnder the heading of climate, we must consider cold 

 weather during the lilooming period. There may not be 

 frosts, but the temperature is so cold in the middle of the 

 day that insects and especially bees will not fly. When 

 the temperatures are around 50° or less, very few bees 



work, and T ha^ 



■nown seasons when we experi- 



enced practically no killing frost, but a protracted cold 

 raw spell. Such a sjjring is generally followed by a very 

 lieht set of fruit. 



Lold rains and driving storms in the spring wash out 

 tlic pollen and prevent the work of insects. In fact, high 

 winds interfere wit;> ihe pollination of tree fruits if they 

 are insect pollinated. The walnut and filbert on the other 

 hand, are pollinated by wind, and a certain circulation of 

 air might be an advantage in such cases. 



Diseases such as scab on apples and pears, and brown 

 rot on the cherry and prune, will often destroy all the 

 blossoms. Trees which have been severely winter injured 

 are often so devitalized that they seem to lack vigor and 

 strength to develop blossoms. 



The busy bee is the most important factor in the pol-- 

 lination of our tree fruits. Fruit districts need more and 

 more of these valuable insects. 



The vigor of the trees is one of the biggest factors in 

 the setting of fruit. When trees come into bloom for the 

 first time, they will often produce a profuse blossoming. 

 Init give a very poor set. The d'Anjou pear is one of the 

 best examples. This tree is often white with blossoms by 

 the seventh year, but it is often very unfruitful. 



As this variety becomes older, it seems to gradually 

 overcome this condition and begins to set better. Un- 

 doubtedly some of the young orchards which bloom 

 heavily but set poorly are somewhat too vigorous to 

 bring about the best setting of fruit. 



In our older districts however, of the northwest, with 

 pear, apple or prune orchards, the lack of vigor is respon- 

 sible for the poor set. Leaving too much weak and de- 

 vitalized wood in the trees, the lack of thorough tillage, 

 arid above all the lack of keeping the soil supplied with 

 nitrogen is the biggest factor in the failure to set fruit. 



In speaking of pollination, there are certain terms which 

 we use that we should all understand. The word "fruit- 

 ful" means the variety has ability to produce fruit. This 

 fruit may or may not have seeds. "Barrenness" means 

 the variety will not produce seeds which v.-ill germinate. 

 'T^'ertility" that the variety will produce seeds which will 

 germinate, and "sterility" that the variety will not pro- 

 duce seeds which will germinate. 



Now while a variety may be fruitful, or even fertile, 

 when planted by itself, still nature seems to favor the 

 crossing of fruits, and where two or more varieties are 

 planted together, there is not much danger but what a 

 good crop will be secured. 



However, there are several glaring exce])tions. For 

 exainple the Spitzenburg apple is almost sterile, and the 

 AMnesap produces no pollen. So that a combination like 

 that would be bad. 



The question is often asked how does pollen affect the 

 fruit ? It seems to affect the size, making the fruit 

 larger, it gives more specimens to the tree and often 

 makes them heavier and firmer. There is a seeming cor- 

 relation between size and weight and number of seeds. 

 Heavy apples have plenty of good seeds. 



Again the quality, and firmness, because of the pres- 

 ence of the seeds, is greatly improved. 



Color is probably not affected directly, for if there is 

 any effect of pollination on color, it would be indirect ow- 

 ing to change in size of specimens. A close checking on 

 this subject over a good many years, causes us to con- 

 clude that color is not generally aft'ected by pollination. 



The bright bands of red on yellow apples, or the dif- 

 ferent colored bands of red on certain apples which run 

 from the stem to the calyx have been attributed as a 

 result of pollination but a close study will show that this 

 is really a bud variation character and not a pollination 

 character. — C. I. Lewis, in American Fruit Grower. 



