Adaptations Of Resistant Stocks To Soils And Climates

Resistance, of course, counts for naught in a stock which comes from a

species unsuited to the soil and climate or other circumstances of the

locality in which the vineyard is to be planted. The several species

used for stocks differ widely in the requirements affecting growth so

that the grower must make certain that the resistant stock he selects

will find congenial surroundings. Stocks in congenial circumstances

are frequently more resistant than others inherently more resistant,

but which are not otherwise adapted to the particular conditions of

the vineyard. Species of grapes vary greatly in their root systems,

some having thick, others slender roots; the roots of some are soft,

of others hard; some have roots going down deeply, others are almost

at the surface of the ground. Manifestly these various root-forms are

but adaptations to loose and heavy, dry and moist, deep and shallow

soils, or to some circumstance of climate. A vine bruised by adversity

is in no condition to withstand phylloxera. Therefore, since the

adaptability of a variety to a soil or climate may be changed by the

stock, the adaptations of stocks to soils and climates must have

attention.



Affinity of stock and cion.



Different varieties of grapes do not behave alike on the same stocks,

and different stocks may affect varieties differently. Even when the

kinship is close, some grapes resist all the appliances of art to make

a successful union; while, on the other hand, quite distinct species

often seem foreordained to be joined. For example, Rotundifolia, which

has the highest resistance to phylloxera of any species, is useless as

a stock because it is impossible to graft any other grape on it, while

Vulpina and Rupestris unite readily with varieties of Vinifera, the

slight decrease in the vigor of the grafted vines serving oftentimes

to increase fruitfulness. Something more is necessary, then, than

botanical kinship. Just what is necessary, no one knows, beyond: that

there must be conformity in habit between stock and cion; that the two

must start in growth at approximately the same time; and that the

tissues must be sufficiently alike that there be proper contact in the

union. Yet these facts do not sufficiently explain all of the

affinities and antipathies which species and varieties of grapes show

to each other. Unfortunately, the grape-grower has had but little to

guide him in selecting stocks and has had to learn by making repeated

trials.