Section 4.1: Post-grafting Management of Vines – Soil Moisture Management
“Field grafting is a great way to change variety or clone and quickly return a vineyard to full productive potential. Field grafters are only partly responsible for the success or failure of field grafting. Understanding what preparation and follow-up is required as a grower to influence the final strike rate is critical. VitiSense provides all the information, techniques, demonstrations and explanations and to ensure your field grafting experience is a positive one”.
Excess Sap Flow
Excess sap buildup behind the buds will force the buds to all forward and reduce the contact of the bud with the trunk. Callusing also seems to become diluted and the buds don’t form a strong union with the trunks. This mainly occurs in low-lying, waterlogged soils, in high rainfall regions and in unseasonal wet Spring seasonal weather.
Testing for Excess Sap Flow
Testing for excess sap flow is simple. Firstly observe wet trunks and excessive “bleeding” of sap underneath the grafted buds. Just squeeze either side of the bud with your thumb and forefinger. If clear sap oozes from the bud then saw cuts will need to be used to alleviate the excess sap and save the bud.
Cutting trunks for sap release is sometime required to release the buildup of sap behind the grafted bud. If this is not released then callusing fails to eventuate and the bud then dries out and fails.
Consult your grafting contractor for advice before making the cuts.
Trunk Cuts to Release Sap Buildup
To alleviate the buildup of sap behind grafted buds, a single cut using a fold out pruning saw should be made under each bud. A knife is not a good substitute for the saw. It is the thickness of the saw blade that make the cut wide enough to release the sap for the period of time to be effective for the bud to callus. A knife cut is too narrow and will grow over and not be effective in releasing the sap for long enough to be effective. The saw only needs to be pulled in a single action towards the person making the cut. Do not make any more cuts deeper than a single movement saw cut. Ask the grafters to show you if you are in doubt. It is rare for these cuts to be necessary and a single cut is usually enough to be effective. Sometime in really wet soils and in some seasons, a second cut maybe necessary and this should be made below the original cut. Always consult your grafting contractor before making these cuts.
