|Viticulture is the production & science of growing grapes for the table, dried fruit or wine making markets. |
Essentially it involves getting the fruit to optimum ripeness and quality for its purpose before harvesting. For the purposes of this website, the term viticulture will only be used with reference to grape growing for wine making.
In nature, it is the vine's mission to create sweet and attractive fruit to invite birds and other creatures to eat then spread the seeds of the grapes to ensure future existence. To do this it uses the leaves of the plant to perform photosynthesis which creates and provides energy for fruit to ripen and to develop sugars. This sweetness ensures there is a great interest in the fruit as a food source. Once consumed and digested, these seeds are deposited in droppings, and so continues the cycle.
However, in viticulture today, desirable wine grape varieties are grafted onto rootstocks which have been developed for, or are naturally adapted to, conditions that benefit the production of quality grapes. These can be rootstocks resistant to phyloxera (a ground dwelling aphid that has devastated vines due to their debilitating and voracious appetite for certain grapevines), drought tolerant rootstocks, nematode resistant rootstock, vigor controlling rootstock, and plenty more.
After a few years in the ground these newly planted vines begin to bear fruit of a quality and volume suitable for wine production.
Firstly, the cycle begins with dormancy in Winter. At this stage the vines are pruned to suit the desired outcome, climate, the soil type, the variety and the goal for the viticulturist which is generally the best quality possible. The factors considered revolve around crop weight as a direct relationship between the amount of fruit a vine produces and the quality of wine that it makes; the balance between vine age and its outputs are considered, as are many other factors, including a positive financial return for the grapegrower. The most common methods of pruning include spur pruning, where approximately eight spurs of two buds per spur remain per arm or cordon, and cane pruning, where two canes are taken from the centre of the vine and wrapped around wire as arms out each side of the vine, leaving approximately 16 buds per cordon. Typically each bud will produce one shoot with generally two bunches of grapes per shoot.
Initial growth starts with the bud swelling, as Spring warms, and then progresses to "wooly bud". Literally a wooly looking cover fluffs out as the bud opens allowing the soft first leaves or "flag shoots" to rise without any interference or damage. About a month later the immature inflorescence appear, the flowers, and over time lose their calyptras which are the caps covering the internal organs of the flower, which will be fertilised by the wind and bees. (It is interesting to note that if you take a cross section cut of a dormant bud and place it under the microscope you can see the viable bunches sitting there to become the fruit. There is generally two or three ensuring in the event of crop damage the vines will have some insurance. Also important to note is the influence of the previous vintages season, can determine the quality of these bunches.) At this point, what happens with the elements greatly determines the success of the vintage. High wind, rain and hail can greatly affect flowering and "fruit set", the viability of flowers becoming grapes. Following fruit set, the vines continue to grow leaves which help to ripen the bunches of grapes. As the berries grow they begin to form bunches with hard green pea like structure. Slowly these berries begin to lose the high acidity and start to accumulate sugars.
Following this is the stage called veraison. At this stage for red (actually called black) grapes, the colour presents as a dull hue of pink. Each berry slowly ripens at different rates sometimes presenting a mottled range of shades in a bunch. As with most fruit the more sun exposure, the greater the colour and ripeness, so canopy managment is important to either allow more or less exposure depending on the climate. Cooler zones sometimes 'leaf pluck' to offer more light to the bunches and warm/hot regions prefer some shading.
During this stage the viticulturist is working to ensure that the canopy allows the perfect balance of sun exposure and air flow, which assists in reducing disease and potential humidity, which is bad for grapes as it produces disease pressures which affects quality and flavours and yield. In addition, this time is spent trimming and maintaining the vines, ensuring their nutritional status is adequate, checking for pests, controlling weeds and irrigating; overall creating the best environment in which to grow ripe fruit with excellent qualities.
Once the warm weather arrives, timing and vineyard practices become more important. Picking time (harvest) is near. The pressure is now on to get all factors in alignment. As the acid, predominantly malic acid (like in apples) falls away and the sugar increases, so does the physiological ripeness of the berries. The seed begins to brown which reduces the hard green spicey sappy tannin, as seen in wines made from under-ripe fruit, the typical flavour profile is coming into balance and the colour is in full bloom for it's variety. These now rich, ripe berries are susceptible to bird attack which would damage the crop. Due to the now tightly bunched fruit (in most varieties), disease becomes more of a risk with reduced airflow. Furthermore, rain and hail damage can split the fruit, also allowing disease to penetrate. Alternatively, excessive heat can push the sugar levels (known as brix or baume) too high, creating unblanaced wines. Hopefully though, this period makes the grapes perfect for harvesting, where they can express concentrated flavours, colours and aroma associated with the variety. At this stage the distance between each set of leaves (internodal space) is getting shorter and slows to a final leaf, with all the energy now focussed on ripening the fruit to its potential.
When the flavours are ripe and balanced and the grower can coordinate the pickers or harverster in line with the weather, and the winery has space and ability to receive and process the fruit, the harvest can begin.
It is regarded that open bunches with smaller than average berry size increases the quality of wines. Due to the fact that much of the associated colour and flavour is derived from the grape skin, it is important to note that a smaller berry has a higher surface to volume ratio. As berries get smaller, the relative surface area increases. This essentially means a concentration or amplification of colour and flavour associated with the skin which influences the final product, the wine. (Imagine two empty red balloons. Fill one with a small amount of water, the other near bursting. Now if you were to blitz them individually in a blender, the coloured parts would be less concentrated in the largest balloon giving a lighter colour. Also imagine these particles as flavour. The smaller balloon would show a higher intensity of colour.)
Following harvest, the vine's canes now begin to lignify, becoming woody instead of a green sapling nature, and carbohydrates are shifted down to the root stores for next season. Simultaneously the fruit for next year will be laid down in the buds. The health of the vines will again determine the success of the following year so at this point the nutritional status of the vines should not be neglected by the viticulturist.
Next, moving into Autumn, is sinescence. The leaves turn a mottled yellow and red and are cast off leaving naked canes. Pretty soon, the pruners will be through to groom the vineyard in preparation for another vintage.
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