Thursday, 8 January 2015

Use of Cosy Tex to accelerate Pinot Noir flowering in a UK vineyard

Champagne and Southern England are climatically distinct. The sea breaches of the English Channel and the North Sea help give us mild winters, but we pay the price with our cool springs and summers. 

Mean monthly temperatures, degrees Celsius. 


















Parity is reached with Champagne in September, but this is a month when both light and temperature become limiting for vines. Frustratingly, acids and sugars become sticky after the autumn equinox, come rain or shine.

The sluggishness of late Spring delays UK vine flowering relative to that of Champagne, and sets veraison back by 2-3 weeks. Pinot Noir and Chardonnay on the Montagne de Reims and Côte des Blancs commence ripening in mid-August, whilst in England, the threshold of the autumn equinox foreshortens maturation and turns October into a month of hope rather than realisation.

Two consequences follow from our stalled summers:

Firstly, our climate gives us no wriggle room: days and weeks lost to bad weather in the summer cannot be made-up later in the season because we run out of effective days; and

Secondly, acids tend to be higher for a given level of sugar vis-à-vis Champagne.

Poor weather increases the financial jeopardy of grape production. In the UK, 2012 was a write-off, whereas Champagne was able to regroup and take advantage of late season warmth.

The issue over acids has no definitive answer. Malic acid can be very dominating, even in sparkling wine. It adds flavour and an impression of weight - useful in our fickle climate - but it is very forceful. Personally, I find it has a greater affinity with Chardonnay than Pinot Noir, and I find its character can become too brutal on clay soils, which seem to bolster its effect. Others will disagree.

Forcing vines to flower early therefore has distinct advantages, particularly for still wine production, and in 2014 I experimented with a product called Cosy Tex to see if I could accelerate early season phenology through to floraison.

Cosy Tex is a woven polythene mesh. The product provides 86% light transmission, is 100% permeable, gives 2-3 Celsius of frost protection and, depending on the area covered and irradiance, can elevate day time temperatures by 3-4 Celsius.

Cosy Tex comes in rolls of various lengths and widths, and can be secured to top wires and vineyard posts by the manufacturer’s clips.

We attached the Cosy Tex in late-April, and achieved an accelerated budburst compared to the rows outside. Early in May, we had three nights of frost, which got progressively harder. The vines underneath the Cosy Tex were untouched during the first two events, but we recorded -4C outside on the third night which resulted in a 60% loss of shoots within the Cosy Tex protected environment, and near 95% loss outside. One issue with the product is that it increases humidity, which raises the frost risk for a given negative temperature value, whilst the advancement of the shoots also increases susceptibility.

In the middle of May we were hit by storm force winds, gusting 55mph. Our method of securing the fabric proved inadequate and the Cosy Tex blew off. The winds didn’t abate for three days, and I finally re-secured the cover a week later. With strong winds forecast at the start of June, I removed the fabric from the vineyard altogether.

Overall, the vines benefited from the covers for three weeks, which brought flowering forward by approximately 7 days,  compared to the surviving uncovered shoots. If we had managed to maintain the covers in place to flowering, then the advantage could have been as much as 2 weeks. We were also unable to study the impact on flowering, which may have been beneficial due to micro-climate warming and reduced wind speeds. We will not know whether the reduced light transmission effected bud flower initiation until this spring.

We will repeat the experiment this year. The use of additional wires passed  through the Cosy Tex should enable us to withstand 50mph winds, and we hope to get a better understanding of the fabric’s full potential by summer 2015.

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