WINTER INJURY IN RELATION TO SPECIFIC FRUITS 329 



line traced for Lombard. . . . In fact a majority of the standard varie- 

 ties, such as Coe Golden Drop, Italian Prune, Jefferson, Lincoln, Moore 

 Arctic, Pond, Shippers' Pride and Washington, would probably be found 

 to conform fairly well to the same limits as Lombard." Of the Japanese 

 plums, "Abundance, Chabot (Chase, Yellow Japan), Hale, Red June, 

 Willard and Ogon seem to be about as hardy as Burbank. Satsuma 

 stands about midway between Burbank and Kelsey." 



In North Dakota, Waldron-°^ states: "Only one species of plum 

 (Americana) can be grown with any success in the State. So far as 

 tried here they are all hardy though some ripen late and most of them 

 are vigorous and productive. . . . All things considered they are the 

 easiest and most profitable fruit to grow in North Dakota. . . . For 

 general cultivation the following varieties will be likely to succeed: De 

 Soto, Forest Garden, Weaver, Cheney, Wolf, Rolling Stone, and Wyatt. " 

 In parts of Minnesota RoUing Stone, De Soto, and Surprise are too late in 

 ripening their fruit to be satisfactory in cultivation, though they are not 

 stated to lack hardiness." For the colder parts of Vermont several 

 varieties have been reported to be as hardy as the sugar maple : Stoddard, 

 Hawkeye, Quaker, Aitkin, Surprise, Cheney, De Soto, Forest Garden, 

 Wolf, Wyant and Weaver, ^os 



In Wisconsin many varieties have brought their buds through a tem- 

 perature of — 38°F. in one winter, though they succumbed to — 23° in 

 another, ^^ indicating that the condition of the tree makes a considerable 

 difference in the amount of cold that can be endured. In view of the work 

 of Chandler with peaches and Roberts with cherries it seems possible that 

 the advancement of the buds when they enter the resting stage may 

 have much to do with their hardiness. No definite data are available, 

 unfortunately, on this point, but the superior hardiness of the Americana 

 group, which is late in maturing, appears to justif.y investigation. It 

 would seem, since plum blossoms are injured more frequently than the 

 woody parts, that maturity might be delayed safely to some extent 

 without unduly increasing liability to injury in other ways.'*^ 



Recent investigations in Minnesota indicate that some of the injury to plum 

 blossoms is associated with early breaking of the rest period. Treatment to 

 increase hardiness by retarding blossom formation and development would tend 

 also to delay the breaking of the rest period. 



The Grape. — Winter killing is not so prominent a factor in grape 

 growing as it is with some of the tree fruits. Two reasons may be assigned 

 for this comparative freedom from injury. First, varieties grown com- 

 mercially in the majority of sections subject to winter killing are de- 

 scended, at least in part, from the native species and therefore profit 

 from the adjustment of the native species to their environments. Second, 

 the difficulty ox seeming satisfactory ripening of the fruit, because of 



