ONE REASON WHY SOME FRUITS DON'T FRUIT 



D. F. JONES 



Connecticut Agricultural Experiment Station 



^T IS gratifying for the home gardener to discover 

 that there are positive advantages in having a number 

 of varieties of a fruit, one tree of each, rather than 

 several of only one variety. But these varieties ought 

 selected with some regard to each other. There can 

 hardly be a greater disappointment than the unfruitfulness of 

 trees which have been carefully tended during many arduous 

 years. Of course it may happen that the varieties planted are 

 poorly adapted to soil and season; but above all proper pollina- 

 tion is likely to be overlooked. 



Some of our most highly prized varieties fail to set fruit unless 

 pollen is available from different varieties of the same sort. 

 Cross-pollination is absolutely essential with many (and gener- 

 ally desirable with nearly all) kinds of fruits in order to insure 

 full, well developed crops. Particularly is this true of Cherries, 

 Apples, Plums, Grapes, and Berries. 



Practically all of the commonly grown Sweet Cherries are 

 self-sterile while none of the Sour Cherries are apparently so. 

 Fortunately the Sour Cherries serve as pollinators for the 

 Sweet Cherries, provided they blossom at the same time. 



Among the list of Apples which fail to set fruit properly when 

 planted singly are many of our most popular sorts such as: 



Rhode Island 

 Greening, Golden 

 Russet, Tolman 

 Sweet, Twenty 

 Ounce, Mcintosh, 

 Gravenstein. 



Other varieties, 

 such as Northern 

 Spy, Esopus Spit- 

 zenburg, Fameuse, 

 and Oldenburg 

 produce some fruit 

 but not in quan- 

 tity when other 

 than their own 

 pollen is excluded. 



This little pot grown tree of Gover- 

 nor Wood Sweet Cherry promise.! 

 a full crop of fruit. To test the 

 effect of pollen from different 

 sources part of the branches were 

 self-pollinated and part were cross- 

 pollinated. Only the flowers that 

 were treated with pollen from 

 another variety set fruit; the re- 

 mainder of the tree was entirely 

 barren (see photograph above) 



Grapes, Brambleberries, and Strawberries are nearly always 

 benefited by cross-pollination. 

 Plums are notoriously self-sterile. 



OBVIOUSLY varieties to be suitable pollenizers for each 

 other must blossom at the same time. A difference of four 

 days in this respect is allowable. It is also desirable that the 

 different varieties come into bearing at the same age. For ex- 

 ample, Northern Spy Apple trees will frequently delay fruiting 

 until nine or ten years after setting, while Wealthy blossoms and 

 often sets fruit at two or three years. One would not want to 

 await the bearing age of the Spy trees to get fruit from the 

 Wealthy. 



The source of pollen has no effect upon the quality or color of 

 the fruit which it starts into growth. A sweet cherry is not 

 less sweet for having been pollinated by a sour. A Greening 

 apple is just as green whether fertilized by Red Astrachan or 

 Grimes Golden pollen . 



APPARENTLY to make the troubles of the fruit grower 

 more trying some varieties are not only self-sterile but are 

 likewise cross-sterile in certain combinations. They do not set 

 fruit any better even when cross-pollinated unless the right 

 kind of varieties are at hand. The Western cherry growers 

 found this out to their sorrow. None of the three leading com- 

 mercial varieties in the West — Napoleon, Lambert, and Bing — 

 are suitable pollinators for each other. These varieties made 

 the best showing in the test orchards where a large number of 

 sorts were being tried out. Here they received plenty of com- 

 patible pollen. But when planted by themselves in large 

 orchards they failed to set profitable crops. In such a case 

 less desirable varieties must be included in the orchards to 

 make the main crop varieties normally productive. Among the 

 Apples, as an illustration, Delicious and Grimes Golden, Duch- 

 ess and Baldwin, Stayman and Graverstein, Yellow Transpar- 

 ent and Stark proved to be unsuitable combinations at the 

 Maine Station in many trials. While Yellow Russet by Bald- 

 win; and Northern Spy, Opalescent and Wealthy, when pol- 

 linated by Ben Davis were particularly good combinations. 



Information is not available in regard to the pollen require- 

 ments of all varieties of fruits, but many failures can be avoided 

 by planting as many different varieties as possible, and this is 

 usually desirable in the home garden for other reasons. In 

 large plantings, it is absolutely essential not to limit the list of 

 varieties too much unless it is shown that the few chosen ones 

 are well adapted to each other in all ways. Much useful infor- 

 mation for prospective fruit growers will be found in these pub- 

 lications: for Apples, Maine Station (Orono) Bulletin 287; 

 for Cherries, Oregon (Corvallis) Bulletin 116; and for Plums, 

 Maryland (College Park) Bulletin 207. 



If trees are healthy and bloom normally, but fail to set fruit, 

 it is well to suspect a lack of suitable pollen. This can be tested 

 by bringing flowering branches of other varieties when the trees 

 are in full bloom and shaking these among the flowers and leav- 

 ing them in the trees for the wind and the bees to complete the 

 job. A good set of fruit will be the reward if the fault lie's with 

 the pollen and if suitable varieties have been brought together. 



SELF-STERILITY in tests made at the John Innes Hor- 

 ticultural Institute in England is clearly shown in the 

 accompanying illustrations. Governor Wood Sweet Cherry 

 was treated by hand with pollen of the same variety and at 

 the same time on different flowers with pollen of Early Rivers. 

 Only the cross-pollinated branch bore fruit and this had a full set. 



