Viticulture
The Grenache vine is characterized by its strong wood canopy and upright growth. It has good wind tolerance (which is useful in the Mistral influenced Rhone region) and has shown itself to be very suited for the dry, warm windy climate around the Mediterranean. The vine buds early and requires a long growing season in order to fully ripen. Grenache is often one of the last grapes to be harvested, often ripening weeks after Cabernet Sauvignon. The long ripening process allows the sugars in the grape to reach high levels, making Grenache based wines capable of substantial alcohol levels, often at least 15% ABV. While the vine is generally vigorous, it is susceptible to various grape diseases that can affect the yield and quality of the grape production such as coulure, bunch rot and downy mildew due to the vine's tight grape clusters. Marginal and wet climates can increase Grenache's propensity to develop these viticultural dangers. The vine's drought resistance is dependent on the type of rootstock it is planted on but on all types of rootstocks, Grenache seems to respond favorably to some degree of water stress.
Grenache prefers hot, dry soils that are well drained but it relatively adaptable to all vineyard soil types. In southern France, Grenache thrives on schist and granite soils and has responded well to the stony soil of Châteauneuf-du-Pape with the area's galets roulés heat retaining stones. In Priorat, the crumbly schist soil of the region retain enough water to allow producers to avoid irrigation in the dry wine region. Vineyards with an overabundance of irrigation tend to produce pale colored wines with diluted flavors and excessive alcohol. The skin of Grenache is thin and lightly pigmented, making wines with pale color and low tannins. Older vines with low yields can increase the concentration of phenolic compounds and produced darker, more tannic wines such as those found in the Priorat region of Spain where yields are often around 5-6 hectoliters/hectare (less than half a ton per acre). Yield control is intimately connected with the resulting quality of wine with yields below 35 hl/ha (2 tons/acre), such as those practiced by many Châteauneuf-du-Pape estates, producing very different wines than those with yields closer to 50 hl/ha (5 tons/acre) which is the base yield for Appellation d'origine contrôlée (AOC) wines labeled under the Côtes du Rhône designation. The strong wood canopy of Grenache makes the vine difficult to harvest with mechanical harvesters and pruning equipment and more labor intensive to cultivate. In highly mechanized wine regions, such as Australia and California, this has contributed to a decline in the vine's popularity.
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