330 FUNDAMENTALS OF FRUIT PRODUCTION 



the shorter growing season, tends to hmit the northward spread of grape 

 culture to points with winter extremes well within the adaptation of 

 the vine. 



Nevertheless, the grape is far from immune to winter injury. Varie- 

 ties with Vinifera qualities predominating or from species native to 

 regions of mild winters have distinct climatic limitations and even 

 the so-called hardy varieties frequently suffer. There is little evidence 

 to connect winter drought with winter injury except in so far as a dry 

 soil freezes deeper. Heavy winter irrigation has proved of no value 

 with Viniferas in New Mexico. '^^ Under very severe conditions root 

 killing may occur; at times the vines are killed to the ground and there 

 are frequent instances of killing of fruit buds because of imperfect matu- 

 rity. Gladwin''^ records three seasons out of eight at Fredonia, N. Y., 

 when the vines did not reach proper maturity. Sometimes heavy rains 

 late in the growing season bring about this condition; again it may 

 be due to the ripening of a heavy crop. The light crop usually following 

 a heavy fruiting is commonly ascribed to exhaustion of the vines but 

 it may be due also, at least in part, to the killing of a large number of 

 imperfectly matured buds. Since the grape bud is compound and mixed, 

 the primary floral parts may be killed and only the secondary shoot 

 develop the following spring. This tends to obscure the kilhng and the 

 sterility of the shoot is attributed to exhaustion following the heavy 

 crop of the preceding season. Gladwin shows that the three lightest 

 crops of the period studied followed the seasons when the sugar content 

 of the grapes (an index of maturity) was lowest. However, since vines 

 which have not borne are affected also much of the immaturity must 

 come from other causes. Indeed, Budd-^ considered immaturity and 

 tenderness to result from the lack of a crop and remarked that the wood 

 of Rogers' hybrids ripened well when bearing a crop but without a crop 

 did not mature. Much greater injury has been reported in low ground, 

 particularly in ground with poor drainage. 



At times very low temperatures, even when the vines are mature, 

 will cause a discoloration of the wood without actually killing the vine. 



Anthony^ reports recent investigations of the practicability of 

 growing certain Vinifera varieties in the eastern United States. When 

 a moderate amount of winter protection is given, by bending the vines 

 down and covering with a few inches of earth, very satisfactory results 

 are obtained. Indeed, with the varieties tested, the hmiting factor 

 seemed to be the heat and length of the growing season rather than tender- 

 ness to winter cold. Anthony states: "A well matured Vinifera is seldom 

 killed outright by the winter even if given no protection, but the effect of 

 the first winter is usually to decrease the plant's vitahty to such an 

 extent that it is unable to reach proper maturity the next season and so 

 is usually killed the second winter. " 



