Posted on January 24 2018
It may not seem, at first, that knowledge of the way in which a vine grows year on year could improve the enjoyment of drinking the fermented fruits of said vine.
But it really can. If drinking, for you, is not just a method of wetting your whistle, parching your thirst or getting tipsy but, rather, is a way of discovering the history, geography, geology, climate and culture of a given region then a little thought about the way in which the vine itself works is bound to add to your enjoyment.
Let's keep it simple. These are the various phases of a year in the life of a vine, starting post harvest.
Late Autumn: post harvest and the vines need to replace carbohydrate reserves in order to be productive the following year. Some warmth and sun required for this.
Winter: Once the carbohydrate reserves are filled the leaves turn brown and either winter frost or low temperatures cause leaves to fall. The vines become dormant and it is a good time to prune the vines in readiness for the following year.
Spring: As temperatures rise above 10 centigrade, the vines start to come back to life. The tips of the canes start to bleed sap as the vines awaken and buds start to swell. This leads to the first sign of greenness as shoots burst from the buds. Growth is slow at first and relies on energy stores filled post harvest. These young shoots grow leaves, which eventually become old enough for photosynthesis and thus further energise the vine.
Late Spring: Around 4 weeks after the shoots first show, the most rapid period of growth begins with shoots growing as much as 1 inch per day. 40-80 days after bud break, flowering begin depending on temperature. Shoot growth generally slows dramatically in this period, unless temperatures are mild and water/nitrogen are plentiful. At the very end of spring, generally, buds are initiated for the following year's fruit, the vine flowers (when temperatures reach 15-20c) and fruit set occurs. Fruit set is the process of pollination and thus transformation from flower into fruit. Fruit set is a crucial period that can be affected by climate - both hot conditions with low humidity and water stress as well as cold, cloudy and rainy conditions can reduce fruit set. On average 30% of flowers become berries, the others falling in a process called 'shatter'.
Summer: The first important occurrence in the summer is veraison - that is the changing of the berries' colour to either red/black or yellow/green. At this point the berries soften and starting gaining sugar and the vine starts to gain carbohydrates in the trunk, arms and roots. Then comes the all important step - the harvest! The harvest date is determined by the ripeness of the berries, and this is essentially a choice for the winemaker. Generally the warmer the conditions the quicker the grapes will ripen, so the sugar levels increase and the acid levels drop. In cooler conditions the grapes will ripen more slowly and usually end up with lower sugar levels and higher acidity. Rain during harvest times can lead to grapes splitting, getting rotten and also a dilution of concentration in the wine.
So, those are the main stages in the life of the vine.
Once you know the crucial points in the year for the vine, you can understand better why 'vintage variation' exists, why frost appearing at the wrong time (spring for example where fruit set can be disrupted or young leaves burned and damaged) can be a catastrophe and how it is somewhat of an art when it comes to choosing harvest dates.
Harvest early and you will have a leaner, more lifted, fresh and vibrant wine. Harvest late and you will have accumulated more sugar, and thus alcohol in the final wine, a fuller body and more richness and perhaps even more complexity.
Let's leave that oh-so-important topic to another blog.