All know that after the sap begins to flow in the spring, a vine, if
cut, will bleed. It seems that at this early period of its development
the sap vessels have no power of contraction. Many suppose that the
same state of things continues throughout the growing season, and are
afraid to cut their vines. But after the vine has begun to grow freely
(when the leaves, for example, are as large as the palm of one’s
hand), a wound very soon contracts, bleeds little or none, and heals
over as in a tree. Any pruning which is necessary upon the old wound
may, therefore, be fearlessly performed.
Some inexpert cultivators, in order to let the sun fall upon the
grapes, pluck off the leaves; hoping thus to procure sweeter grapes.
This is the very way to have acid fruit. Where is the sugar prepared
for the cluster but in these very leaves which are taken off? Without
leaves, the sap which flows into the cluster has undergone but
imperfectly those chemical changes on which the fruit depends. Every
leaf in the neighborhood of the fruit is precious.