‘Physiological’ pruning
A central focus of pruning is to prevent drying out and the resulting constrictions that would compromise sap flow.
When performed correctly, the method described results in a few small, superficial wounds that do not cause significant phytostress, do not impair the vine's sap flow and are therefore beneficial from a sap flow and phytosanitary perspective.
One-year-old wood
The one-year-old wood – the shoots from the previous year – is cut, leaving the crown at the base of the shoot. This results in very superficial drying, which does not affect the central flow path. If the crown is resected at the level of the internode in the sense of a ‘Coup rasee’, deeper drying occurs, which leads to a constriction and impedes sap flow.
Two-year-old wood
The cut of the 2-year-old wood from the previous year, on the other hand, is not made at the level of the departure of the parent branch, but rather leaving a stump that is no less than twice the cross-sectional area in length. The subsequent drying out of the stump extends directly to, but not into, the branch of the internode of origin, so that its sap flow is not compromised.
Perennial wood
The same rule applies to pruning perennial wood in the head area and prevents, among other things, the typical balding of the head area with all its negative consequences (see phyto-surgery). Failure to comply with this rule results in the familiar bald heads pruned using the old method, with all the negative effects this has on the health of the vine.
The sap flow compromised in the bare head area (see above) by constrictions and bypass circuits is replaced by ‘physiological’ pruning with an unimpeded and vigorous supply – from the roots to the shoot tips.