20 



From what we can learn, the soil itself has no direct effect, but 

 a weak root-system due to defects in the air, heat, texture, or mois- 

 ture of the soil, will not be in a condition to supply the necessary 

 water and food to a fruiting vine. Excess of nitrogenous sub- 

 stances in the vine due to over-manuring or to over-cultivation of 

 a rich border, easily aggravate "shanking." It is said by 

 good authorities that "shanking" occurs when the vine is deficient 

 in potash, and they recommend this to be supplied in some form 

 as a manure to the soil. Dropping of the grapes is also a common 

 result of any disease of the foliage, stems, or roots of the vine. 



BLANCHING. 

 " Chlorose" or " blanching," is a disease which has caused much 

 trouble in the south of France. The vine-leaves lose their deep 

 green shade, then become yellow or completely blanched. The 

 loss of colour generally begins near the margin of the leaf, and 

 spreads inwards between the veins ; the affected parts may or may 

 not become withered. Young green twigs sicken like the leaves, 

 and may dry up. The woody branches are retarded in growth, 

 and new leaves given off remain small and blanched. As the 

 malady almost always develops before the flowering period, both 

 flowers and young fruit are stunted and discoloured, and probably 

 dry up or fall off. French experience shows that chlorose is worst 

 on very limey calcareous soils. On such soils the vines sicken in 

 the first year, and gradually lose their vigour ; death may ensue, 

 but frequently the vines recover gradually each year, and the 

 chlorose may disappear. Where the soil is less calcareous, the 

 disease is less intense. On clay or siliceous soils, chlorose only 

 appears in some cold wet spring, when yellow patches may appear 

 on the leaves, but growth is hardly interrupted, and if the weather 

 improves, all comes well again. The primary cause of chlorose 

 is the presence of too much carbonate of lime (limestone or chalk) 

 in the soil, and its action is assisted by any condition of the soil 

 which increases the amount of soluble lime. This is further 

 assisted by want of water, light, heat, or air, which defects tend to 

 weaken the general health of the vines. The disease is diminished 

 by any mode of cultivation which promotes good drainage in the 

 soil, or which strengthens the growth of the vine. Above all, 

 applications of sulphate of iron (green vitriol) to the soil round the 

 roots of the vine do most to cure chlorose ; this is the case, even 

 though the soil naturally contains iron. As many of the great 

 vine-growing districts of France have a calcareous soil, chlorose is 

 a serious disease, and, during the Phylloxera epidemic, it assisted 

 in almost exterminating the vine, and in ruining many a grower. 

 During recent years, however, great progress has been made in 

 checking both Phylloxera and chlorose. This is done by selecting 

 vines produced by grafting the European vine (Vitis vinifera) on 

 stocks of American vines. Briefly, however, certain varieties of 

 Vitis vinifera grow fairly well on calcareous soils (e.g., Folle- 

 Blanche, Pinot, Colombeau, etc.) ; these are grafted on stocks of 

 the American Vitis Berlandieri, which is found wild only on 



