314 FUNDAMENTALS OF FRUIT PRODUCTION 



The Plum. — Iowa's experience with plums in the winter 1898-1899 is 

 thus stated by Craig :^^ "Plums, native or European, worked on peach 

 or Myrobolan killed, on Marianna badly injured, on Americana slightly 

 injured, but these recovered rapidly except where they were, in a few 

 instances, permanently inj ured .... Americanas worked on peach roots 

 escaped where well rooted from the cion. Sand cherry stock (Prunus Bes- 

 seyi) has been used to some extent in the state. In no case have I found 

 these roots injured in the slightest degree. In passing I may add that ex- 

 perience has not yet developed the ultimate effect of this stock upon the cion. 

 Thus far its dwarfing influence upon varieties of the Americana type is 

 satisfactorily demonstrated. Domestica plums on own roots fared better 

 than the same varieties on peach, Myrobolan or Marianna." Elsewhere: 

 "On the matter of plums the sand cherry {Prunus Besseyi) appears to be 

 the hardiest form we know anything about. Native plums in the college 

 orchard on this stock were entirely uninjured last winter, while the same 

 varieties on Americana stocks alongside were injured or killed." Carrick 

 places Myrobolan in the same group as Mazzard cherry and pear for 

 hardiness. 



The Grape. — Reports of root killing in grapes are relatively rare. The 

 comparatively deep-rooting habit, combined with sufficient tenderness of 

 tops to discourage grape growing in regions where root killing is common, 

 may account for this apparent resistance. Furthermore, most grapes 

 of American origin are in fact hardy varieties on their own roots and if it 

 be safe to reason from the analogy of cion-rooted trees, the roots should 

 share the hardiness of the tops. Niagara has been reported to be notor- 

 iously tender in bud and root.^* Hansen^^ reports considerable trouble in 

 parts of South Dakota from root killing; the New York vineyards suffered 

 extensive damage in the winter of 1903-1904. Hedrick^- suggests that 

 the St. George (a variety of rupestris) stock used in some experimental 

 work at Geneva, N. Y., may be more hardy than certain others and notes 

 that American varieties on their own roots winter killed extensively. 



Carrick made numerous laboratory freezings of six varieties of grapes to 

 compare their relative hardiness. The varieties studied, representing several 

 species, fell readily into two classes, viz., Clinton, Concord and Diamond, "rather 

 resistant to cold" and Cynthiana, Lindley and Norton, "relatively easy to kill 

 by freezing." Within the groups the differences in hardiness are not striking. 

 For the hardier group, "Only scattering injury is recorded at —11°, —12°, and 

 — 13°C. At an exposure of —14.5°, 22 out of 27 Concord roots were uninjured, 

 and only a trace of cambium and cortex injury was noted in the remainder. 

 ... At —18°, however, the cambium, phloem, and cortex tissues were com- 

 pletely injured in all roots, with some xylem injury in the Diamond and the 

 Concord. . . . The limits of this second group (Cynthiana, Lindley and 

 Norton) he between —10° and — 12°C., the roots usually undergoing con- 

 siderable injury at —11°. In relative hardiness this places these varieties 



