Yields

Flowering

Lower yield predictions after inclement December.

SOPHIE PREECE

“ROLLER COASTER” temperatures over flowering have resulted in poor fruit set in Marlborough’s Sauvignon Blanc vines, leading to predictions of an average or below average crop this year.

With budburst a week behind normal and winery space compromised by the November earthquake, a drop in vintage expectations is a welcome story to those concerned by the high inflorescence numbers counted in November last year, indicating the potential for a crop as large as 2016.

Forrest Estate’s John Forrest has lost around 20% of his crop because of a long flowering period in December, which was rain-ridden with variable temperatures. “I think because there was a high bunch number, and now we have a low berry number per bunch, we may be back to an average or just below average crop,” he says, happy about that result. “Previously everyone was talking about a 2016 again, with a 20% – 25 % above average crop. Well I think that’s gone.”

In a recent Vine Facts, Marlborough Plant & Food Research A cool December has impacted on berry numbers. (MPFR) Scientist Rob Agnew called January’s weather pattern a roller coaster of temperatures. The same variable temperatures occurred in Marlborough in December, over the period of Sauvignon Blanc flowering, he says.

Fellow MPFR Scientist Mike Trought says studies indicate that grape vine flowering occurs approximately two days after a weather event. A hot day might kick off the process, but a cool change a few days later can stymie it, resulting in the loss of flowers. “When you think about it, grape vines are not very good at setting fruit,” he says. “Each Sauvignon Blanc flower has four ovaries in it. The chances of getting a fertilised ovary is probably only about 10%.” The difficult flowering period may result in an increase in Millerandage, or hen and chickens, in some varieties, where small seedless berries cluster alongside fertilised berries with set seeds and normal size. However, Mike says that, in general, seedless Sauvignon Blanc berries do not develop to the same extent as a variety like Pinot Noir, and it is less likely to be a problem in Marlborough’s main variety. The lower yields may also be an advantage in this slightly later season, advancing ripening a little earlier than might have otherwise been expected, he says.