Trellis Trials: A case for Scott Henry in Sauvignon

Dr Stewart Field, a lecturer at Nelson Marlborough Institute of Technology (NMIT), says research conducted over the past two seasons, in trials at Wither Hills and wine production and analysis at the Bragato Research Institute (BRI) and NMIT wineries, showed multiple advantages of the Scott Henry system compared to vertical shoot positioning (VSP) four-cane pruning.

The positives of decreased disease risk and increased yields “dwarf” the extra management costs of the system, which sees shoots trained down to a bottom wire at flowering, extending the exposed canopy and fruit. “I can’t see why more growers located on vigorous soils in Marlborough are not using Scott Henry,” he says.

Wither Hills Viticulturist Ben Burridge began the trial work after the company took over a lease block of grapes with some Scott Henry trellis in place. He had already seen the success of the system, having bought fruit in a botrytis-afflicted year from a producer using Scott Henry trellis. “We were getting fruit from across the valley, and we noticed the difference in quality,” he says. “Since the infrastructure was there, we decided to give it a go.”

The decision was not without its challenges, with frost in the first year leading Ben to switch back to VSP, having been informed of the difficulty of managing their new system on frost-damaged vines. Labour supply issues the following year made it “a mission to get the right people in at the right time”, with shoot training in November and December, while other work is in full swing.

That year it cost the company an extra $2,000 per hectare to implement the alternative system, whereas the year after, when they had better labour and timing, it was only $1,000. In a normal year there are at least two more passes required by the system, first positioning the shoots two or three weeks after budburst, then dropping them around flowering. Stewart says there is no more effort required in pruning and the additional cost is easily covered by higher yields and better-quality fruit, with less bunch rot.

In the second year of the trial, in 2022, the yield was close to 6 tonnes per hectare greater in the Scott Henry vines, with no significant difference in ripening, although Scott Henry had slightly higher brix.

The increase in yield was largely due to a “significant” increase in berry size, as well as a “slight” increase in bunch number and berry number/bunch. There was no difference in shoot number.

Total acidity was significantly higher in the VSP “largely due to significantly higher malic acid”, says Stewart. There was also significantly higher botrytis pressure in the VSP vines. When it came to chemical analysis of the wines, the VSP fruit produced significantly higher thiols in both vintages, but there was no difference in methoxypyrazines.

One cautionary note Ben raises is to be vigilant about the timing of sprays, especially in November and December, because the canopy can be “sticking out and crazy” before being trained down, making it challenging to get coverage. “But once you have dropped it looks really good.”

Delegat uses Scott Henry in all its vineyards, having trialled the system in 2009 and implemented it across the operation by 2012. Company viticulturist Rob Trought recalls Dr Richard Smart (see Smart Choice sidebox) saying, “don’t tell me you can’t do it; prove to me you can’t do it.” It turned out they could, and Rob says the benefits were quickly apparent, including higher yields and less disease, while the company’s fruit was often remarked upon as being cleaner in tougher years. “It gives us more resilience in wetter seasons.” However, he says it can be challenging to start with, and he applauds the operations supervisors and managers who have made it a standard operation in the vineyards.

Stewart says despite the benefits of Scott Henry trellising, and positive outcomes for companies like Delegat, there is resistance to change. He also knows of growers who have tried the system and slipped up on timing – too early to catch all the shoots or increased breakages, or too late because the tendrils have already attached to an upper wire. “I think that’s what’s happened with a few growers – they have tried it and got that bad result."

Smart Choice

Dr Richard Smart, former Government viticulturist at the Ruakura Research Centre in Hamilton, first met Scott Henry in 1983 in Oregon. “I was impressed with the system which Scott had developed, based on canopy management principles,” he writes from his base in Australia.

“Trials in Gisborne, Hawke’s Bay and Marlborough demonstrated the benefits of conversion of standard New Zealand vertical shoot positioning trellis.” Richard describes “consistently higher yields by 30% or more, typically earlier ripening, less bunch rot, and less need for leaf removal. All of this with very small increases in cost”.

Richard says the method has proved very successful for Sauvignon Blanc and other varieties in Marlborough, and research results with red varieties have shown improvements in quality. The extra costs are one movable foliage wire below the head, and an extra 25 to 30 hours per hectare for a shoot positioning pass downwards, about two weeks pre-flowering, he adds. “A major company in Marlborough has used this method successfully for over a decade and in Hawke’s Bay and Australia. Why not follow their lead?”