GRAPEGROWERS from the Barossa have decided to pull or graft their vines in the lead up to spring to create a more premium, profitable and sustainable vineyard business. More than 50 growers turned up to hear McLaren Vale-based viticulturist Tony Hoare share his grafting knowledge at an information session presented by the Barossa Grape & Wine Association.
Grapegrowers are reworking vineyards in an effort to better meet winery expectations and keep pace with the ever-changing popularity of different winegrape varieties.
There is a consolidation of what varieties work best in particular regions and have the greatest value for growers and wineries into the future according to Hoare Consulting viticulturist Tony Hoare.
Hoare, who has more than 20 years’ experience grafting grapevines in different wine regions, says field grafting is a popular option for reworking vines to change varieties or clones.
And says there are even more frequently asked questions about how to get it all done as an option to replanting, including the following.
T BUD, CLEFT GRAFT OR CHIP BUD?
Each of these methods of grafting grapevines have their merits. Chip budding is the most popular due to speed in covering large areas and high strike rate.
Strike rates of 90 per cent or more should be expected from field grafting using the chip bud method.
WHAT CAN I GRAFT?
Almost any combination is possible with a trunk diameter above the size of a 10 cent piece.
While an older trunk diameter is no limitation, they are more prone to diseases such as Eutypa, which will reduce the area for bud placement and can spread to kill the bud with time.
Successful strike will also depend on compatibility of the bud and rootstock, as well as virus status of all vine material which can be tested.
CAN I DO IT MYSELF?
Grafting is a skill some people acquire quickly while others have more difficulty. Part of the skill relies on having four cuts made well.
The back of the bud needs to be perfectly flat, and the base of the bud needs to have enough of an angle and surface area to allow for a successful callus to form.
The third cut made on the rootstock with a budding knife should be flat and have as small a surface area as possible exposed once the bud is placed in the cut.
The fourth cut is a small wedge made at the bottom of the grafting cut where the bud will sit. A dull ‘snap’ sound should be heard when the bud is pushed into the wedge cut on the trunk and should sit firmly prior to taping.
Consistency of cuts is required to ensure a good strike.
TAPING: HOW IS IT DONE?
The art of taping is another one of those things which look easy – until you try it. But get it wrong and you can bring undone all the effort of completing a perfect graft.
Hoare says the white, one-inch tape is best.
“The textured version with good elastic strength makes taping easier,” he adds.
“On average you can budget for 50 vines per roll – around 50m.”
This will increase with trunk diameter and depend on the efficiency of the taper.
A figure-eight taping pattern going above and below the bud should allow an ‘eye’ pattern to secure the bud in place. If the ‘eye’ is not as small as possible without covering the bud, it is likely to dry out and die.
The ability to cover the ground in good time is an important consideration for taping and most experienced grafters have a separate taper to follow them and stay no more than five vines ahead to lower the risk of buds drying out.
Full article in the September 2014 issue of Grapegrower & Winemaker.