Saturday, May 26, 2012

Pruning Assessment

We use the pruning season to assess how we are going to set up vineyards for next vintage. The number of buds left at pruning time will determine the shoot density through the next growing season. High shoot densities lead to shaded canopies that in turn can produce low grade red fruit at harvest.

Shoot density is defined as the number of shoots per metre of canopy. This number varies depending on the type of trellis system, for example, the ideal density for vertical shoot positioned (VSP) trellis system  in the Adelaide Hills is 10-15 shoots per metre. For semi-sprawling canopies, shoot density can reach levels of up to 30 shoots per metre.

Here are a couple of reference vineyards we have worked on. 

1. Trying to improve Shiraz quality.

This McLaren Vale Shiraz vineyard that was shoot thinned as our trial for Vintage 2012. This vineyard was thinned to approximately 20 shoots per metre. This was an attempt to let more light into the vineyard canopy.

For Vintage 2013 we assessed this vineyard as having moderate vigour.

The vineyard has moderate vigour, with canes 60cm-140cm.

Before pruning.


After pruning.

The most common pruning system used throughout McLaren Vale is “Spur Pruning” whereby last year’s canes growing from the cordon are pruned back to two nodes to form a ‘spur’.

If the vines were more vigorous, then in an attempt to balance vegetative growth and increase cropping potential, we could have retained more buds. This can be done using a Finger and Thumbpruning system. It is similar to the spur pruning system but rather than reduce two canes to a normal two bud spur, the upper cane is retained and shortened to around 4 buds.

Pruning detail. This shows that it was difficult to leave vertical spurs.
2. Maintenance Pruning

This vineyard grew a Shiraz fruit to a high grade in Vintage 2012. They are aiming for a repeat this season by keeping their canopy open by close pruning making sure spurs are upright and the buds per metre are 18-20.

After pre-pruning.

Pruned - note the straight spur positioning.

This vineyard is leaving 18 buds per metre and will produce a low to moderate shoot density for Vintage 2013. This pruning job was assessed as being adequate to set the vineyard up for A-Grade target.

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