Sunday, December 09, 2012

Grapevine Growth

It's amazing how fast grapevines grow.
From the pictures below you can see their development from early September to early December.
This year the Pinot Noir seems to have developed much larger leaves than normal and certainly more vigorous shoot growth. This may be the result of our wet spring and plenty of residual soil moisture.
We have been green pruning fairly severely already in order to thin out the fruitless shoots. This allows more air circulation around and through the canopy to help prevent fungus.
A less dense canopy also allows better spray penetration.
In addition it also prevents shading ie. allows more sunlight onto the leaves and bunches to assist in the ripening process. This means increased sugar levels (higher resultant wine alcohol), increased colour in red grapes, increased tartaric acidity and overall better varietal flavour.

Meanwhile the Pinot Noir bunches are developing. They have reached the 31st stage according to the Eichhorn and Lorenz system ie. berries pea size, bunches hanging down. The berries will continue to 'swell' until they are touching. This is known as bunch closure. Some varieties 'close' more than others. Chardonnay for instance has very tight bunches while those of Cabernet Sauvignon are more open. Tight bunches always have problems with botrytis in wet conditions and it is always essential to get a preventative spray on before bunch closure as a follow up to the first at 80% cap fall.

              Grape berries follow a double sigmoid growth curve. The initial phase of growth results from cell division and expansion. Then the growth slows. This  is known as the lag phase. This is not a physiological growth stage, but an artificial designation between the two growth periods of the berry, the second of which is ripening. This is signalled by veraison or colour change.

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