It’s been said a million times before, great wine is made in the vineyard. The key essential ingredient in any great wine is having wonderful fruit to begin with, and once a winemaker has that, they do their level best not to mess it up. Essentially, no matter how great a wine maker is, they cannot make a silk purse out of a sows’ ear, or to put it into the vinous terms, they can’t turn ordinary grapes into wonderful wine.

In many ways the Holy Grail of wine starts with the grapes and the grapes begin with viticulture, and that is why viticulture is so important because it is the foundation stone of all wine, good and bad. Knowledge of viticulture, even at a very basic level, is not important for the enjoyment of wine, but that knowledge can certainly help wine lovers understand, to a certain extent, a little about why they may like or dislike a particular wine.

“Some of the characteristics that create green flavours in the wine are generally held in the leaves and they come into the fruit during the ripening period. With good canopy management, or with vines that are old, there are very few leaves around the fruit and the grapes are capable of generating lovely fruit flavours which are dominant. The green flavours basically disappear early on.

In today's environment, much of the fruit has been hedged and has a lot of lateral (leaf) growth around the fruit which allows the green flavours to come back in. The growers then leave the fruit on the vine until those green flavours have gone, but by that stage, by the time the grapes seem to be fully ripe, they are into the high alcohol level and the resulting grapes are into the black end of the flavour spectrum. I don't think that's good for the wine because once the grapes get into that black flavour spectrum, I think you simplify it because you have got rid of a large percentage of the flavour profile.

When you pick the fruit, its unlikely to be perfectly balanced (ripe) through the whole vineyard but when you have waited so long to get the grapes physiologically ripe, you have reduced the flavour spectrum to a small percentage of its possible complexity. The biggest problem we face is that if you are chasing physiological ripeness and don't have the ability to work the vineyard as well as you would like to; viticulturally you are going to find it very difficult to make complex wine. You are going to wind up with a more simple wine with higher alcohol levels and a sweeter wine.”

“The balance between physiological (flavour) ripeness and sugar ripeness is a focus for viticulturists in every vineyard region, be it Burgundy or McLaren Vale.  Generally the superior sites will be physiologically ripe and sugar ripe at around the same time.  "Green flavours" are generally present in the fruit at berry formation and begin to decline in concentration during the ripening phase which begins at veraison.  At the same time tannins 'ripen' and fruit flavours and colour build.  The final composition of the fruit is a balance between the rate of 'green decline' and 'fruit flavour increase'.  The conditions that favour rapid flavour increase and green decline are (simplistically) high light intensity and warmer temperatures.

In Australia it is generally felt that sugar ripeness is often reached before physiological ripeness.  It is therefore necessary to try and accelerate the rate of physiological ripening relative to sugar ripening.  We try and achieve this by increasing exposure of the fruit to the sun.  There are a number of ways of achieving this.  Firstly, over-vigorous vines produce lots of leaves and shaded fruit. Choosing a low vigour site is a good start.  Moderate, considered inputs of water and fertiliser also assist in reducing vine shoot growth.  Heavy trimming can promote lateral growth which further congests the fruit zone with leaf, so naturally devigorating the vine is preferable to chopping off excess growth.  Careful irrigation management can, in the right soils allow us to mildly stress the vines to the point where some of the leaves in the fruit zone are shed.  We generally begin irrigating straight after this in order to maintain the rest of the leaves in good health.  Canopy lifting during the season, leaf plucking at fruit set and removal of unnecessary shoots soon after budburst can also be used to produce an uncluttered fruit zone. 

I am unaware of any compound that is held in the leaf that moves to the fruit in response to trimming or lateral growth.  I suspect that vines that require heavy, multiple trimming are naturally over vigorous and produce 'greener' fruit at higher sugar due to the mechanism described above.”

Even a viticultural cretin like me can understand this, how wonderfully simple it all sounds, if only it was that easy in practice. However this information certainly helps to understand the process and ripening grapes successfully.

My thanks to both Mark and Toby for their comments.