SELF-STERILITY IN APPLES 



C. B. S., U. S. DEPT. OF AGRICULTURE. 



ABOUT ten years ago Prof. M. B. 

 Waite called attention to the abso- 

 lute sterility of certain varieties of 

 pears when fertilized with their own pollen. 

 Later Prof. F. A. Waugh and others showed 

 that all the varieties of Japanese plums and 

 practically all the native American plums are 

 self-sterile, and will not bear any fruit what- 

 ever, unless crossed with other varieties. 

 This work led to similar investigations with 

 apples, and very interesting results have been 

 obtained. The Ben Davis apple, which 

 proved self-sterile at the Kansas experiment 

 station, was found entirely self-fertile at the 

 experiment stations in Rhode Island, Ver- 

 mont, and Canada. Even in Kansas, where 

 26 per cent, of the self-fertilized blossoms 

 set fruit, it was found that the self-polli- 

 nated fruit was not so large or so vigorous 

 as the fruits from cross-fertilized blossoms 

 on the same tree. Besides, a much larger 

 proportion of the self-fertilized fruits drop- 

 ped before they reached the size of a hazel- 

 nut than of the cross-pollinated fruit. 



The following alphabetical list shows the 

 varieties of apples that have thus far been 

 found by actual trial at one or more experi- 

 ment stations to be self-sterils : Astrachan, 

 Relleflower, Ben Davis. Blenheim, Canada 

 Red, English Russet. Fameuse. Gravenstein, 

 Grimes Golden. Hawley. Huntsman, King, 

 Mann, Northern Spy. Porter, Primate, Rib- 

 ston, Rhode Island Greening. Roxbury 

 Russet. Spitzenberg, Stark. Talman Sweet, 

 Wealthv. Williams Favorite. Willow Twig 

 and Winesap. 



The following varieties have been found 

 more or less self-fertile and capable of pro- 



ducing some fruit when standing alone, and 

 not cross-pollinated : Alexander, Astra- 

 chan, Baldwin, Ben Davis, Bough, Che- 

 nango, Early Harvest, Esopus, Fa- 

 meuse, Jonathan, Ontario, Rhode Island 

 Greening, Smith Cider, Twenty-Ounce and 

 Yellow Transparent. With many of the 

 varieties in this list not more than one blos- 

 som in a hundred set fruit when self-ferti- 

 lized. With scarcely any was a good crop 

 secured, and in nearly every instance the 

 fruit has been smaller and less desirable than 

 cross-pollinated fruit. The conclusion seems 

 inevitable that large blocks of a single va- 

 riety of apples should never be planted. Va- 

 rieties should be intimately mixed in the or- 

 chard to insure cross-pollination. These 

 varieties should be such as will blossom 

 about the same time and be capable of cross- 

 fertilizing each other. 



With respect to. the latter point, Jonathan, 

 Huntsman and Cooper Early proved especi- 

 ally valuable as pollenizers at the Kansas ex- 

 periment station. Prof. G. H. Powell, at 

 the Delaware station, found that Paragon, 

 Staymen, Winesap and Lily of Kent, all 

 weak pollen bearers except the latter, to be 

 inter-sterile, and should therefore never be 

 planted together in commercial orchards for 

 the purpose of cross-pollination. Further 

 work along these lines to determine what va- 

 rieties bloom together and are most suitable 

 for pollenizing each other is very desirable. 

 And since varieties behave differently toward 

 each other in different sections of the coun- 

 try, these data should be determined in many 

 different localities. 



