POLLINATION OF PLUMS 281 



instance, experience has shown that the Tragedy can be brought to 

 greater bearing by the presence of other varieties of European 

 species, and the Hungarian is well pollinated by the Peach and the 

 Grand Duke plums. The bearing of Wickson is greatly increased 

 by association with Climax. It is clearly demonstrated that planters 

 of plums should pay attention to association of varieties except in 

 the case of the French and the Sugar prunes, neither of which re- 

 quire cross-pollination. 



Careful studies of prune pollination have been made during the 

 last seven years by Prof. A. H. Hendrickson both with reference to 

 varieties and the desirability of bees as pollinating agencies and 

 the results published in Bulletins 291 and 310, which can be had by 

 application to the University Experiment Station at Berkeley, and 

 they should be studied by all planters. The work is still in prog- 

 ress in 1921 and new results being recorded which can be had by 

 correspondence with the Division of Pomology at Berkeley. 



THINNING PLUMS 



In shipping plums it is essential to thin the fruit systematically 

 as stated in Chapter XII, to get fancy sizes. The^ smaller varieties, 

 such as Beauty, Diamond.etc.. should be left about an inch apart, 

 while Gaviota, Formosa, Tjrand Duke, Santa Rosa and Wickson 

 may be left two to two and a half inches apart. Imperfect plums 

 should be removed first, and in all cases care must be exercised to 

 avoid loosening the stems of those remaining. 



IRRIGATION OF PLUMS AND PRUNES 



Irrigation of plums and prunes to secure size of fruit and thrift 

 of trees, is undertaken in different producing regions as local con- 

 ditions may require. The discussions in Chapter XVI have par- 

 ticular applicability to the plum family. 



VARIETIES OF PLUMS AND PRUNES 



As with other fruits, comparatively few varieties of the plum 

 are largely grown in California, and the list is continually changing 

 by rejection of old varieties and introduction of new which, for ship- 

 ping purposes, are largely of Burbank origin. 



The 1920 conferences of growers, canners and nurserymen 

 reached the following conclusions on plum varieties : 



Approved for Shipping. Anita, Beauty, Cal. Blue (Vacaville), Burbank, 

 Climax, Diamond, Gaviota, Giant, Grand Duke, Duarte, Hungarian, Kelsey, 

 President, Santa Rosa, Tragedy, Wickson. Additional for home use: Apex 

 Plumcot, Damson, Satsuma. 



Disapproved. Clyman, Coe's Golden Drop, Abundance, Botan, Fellen- 

 burg, Formosa, German, Paragon, Red June, Standard, Sugar. 



Approved for Canning 1 . The canners recommend planting 25 per cent 

 Washington, 40 per cent Yellow Egg, 25 per cent Jefferson, 10 per cent 

 Bavey's Green Gage. Disapproved: Imperial Gage. 



