In 1990 almost 10% of Italian vineyards, or more of 100,000 ha/ 247,000 acres, were planted with some form (biotype/clone) of Sangiovese. In its various clonal variations and names (Brunello, Prugnolo Gentile, Nielluccio, Morellino, etc), Sangiovese is the principal vine variety for fine red wine in Toscana, the sole grape permitted for Brunello di Montalcino, and the base of the blend for Chianti, Chianti Classico, Vino Nobile di Montepulciano, Morellino di Scansano and the vast majority of Supertuscan. It is, in addition, the workhorse red grape of all central of Italy, widely planted in Umbria (where it gives its best results in the DOCG wines Torgiano Riserva and Montefalco Rosso), in the Marche region (where it is the base of Rosso Piceno and an important component of Rosso Conero), and in Lazio. Sangiovese can be found as far afield as Lombardia and Valpolicella to the north and Campania and Puglia to the south.
Yet in 2004, researchers Vouillamoz and Grando at San Michele all'Adige identified the parents of Sangiovese: the Tuscan "cherry grape" Ciliegiolo and Calabrese Montenuovo, an obscure variety found in Campania though probably originating from Calabria. (…) Ciliegiolo was already cited in 1590 in Toscana by Giovanvettorio Soderini under the name Ciriegiuolo. In his book Soderini also mentioned the variety Sangiogheto.
This is commonly accepted as the first mention of Sangiovese, but there is no evidence that Sangiogheto actually was Sangiovese. Indeed, when Soderini writes about the way to make a very good wine, he says "beware of the Sangiogheto, who thinks to make wine from it will make vinegar".
Moreover Sangiovese was rare or almost unknown in Toscana prior to 1700, whereas Trebbiano and Malvasia were the most widespread grapes. This is consistent with Sangiovese probably being born sometime before 1700 from a spontaneous cross between Ciliegiolo and Calabrese Montenuovo.
Calabrese Montenuovo is not a register variety and its true identity is still not known, but researchers were prompt to make it clear that it is not Nero d'Avola from Sicilia, a variety often called Calabrese. In fact, the name Calabrese is commonly used for several distinct cultivars in Italy, even from Sangiovese.
Cosimo Trinci, in 1738, observed that wine made solely with Sangiovese were somewhat hard and acid, but excellent when blended with other varieties, a judgment echoed by Giovanni Cosimo Villafranchi in 1883. Bettino Ricasoli found a way to tame Sangiovese's asperity - a substantial addition of sweetening and softening Canaiolo - which became the basis of all modern Chianti and of Vino Nobile di Montepulciano (although Ciliegiolo, Mammolo and Colorino as well as the white grape Malvasia and, especially, Trebbiano were subsequently added to the blend). The use of small oak barrels, begun in 1970s, can be seen as a modern solution to the same problem of excessive asperity.
Conventional ampelographical descriptions of Sangiovese, based on the pioneering work of G. Molon in 1906, divide the variety in two families: the Sangiovese Grosso, to which Brunello, Prugnolo Gentile and the Sangiovese di Lamole (of Greve in Chianti) belong, and the Sangiovese Piccolo, of other zones of Toscana, with the implicit identification of a superior quality in the former. Current thinking is that this classification is too simplistic, that there is a large number of clones populating the region's vineyards, and no specific qualitative judgment can be based on the size of either the berries or the bunches. Significant efforts are at least being made to identify and propagate superior clones; mass-selection in the past sought principally to identify high-yielding clones without any regard for wine quality. The variety adapts to a wide variety of soils, although the presence of limestone seems to exalt the elegant and forceful aromas that are perhaps the most attractive quality of the grape.
Over production tends to accentuate the wine's acidity and lighten its color, which can also oxidize and start to brown at a relatively young age. Too often Sangiovese has been planted with scant attention to exposure and altitude in Toscana, where the vine is cultivated at up or even beyond 500m/1,640 ft. A good part of contemporary viticulture research in Toscana - which involves increased vine density, lower yields per vine, better clones, more appropriate rootstocks, lower vine training systems, small oak barrels, more suitable supplementary varieties for blending different temperatures and length of fermentation - is dedicated to resolve a single problem: how to put more meat on Sangiovese bones, how to add flesh to its sizable, but not always sensual structure. Throughout modern Toscana, Sangiovese is now often blended with a certain proportion of Bordeaux grape Cabernet Sauvignon, whether for Chianti or highly priced IGT and Vini da Tavola.
Jancis Robinson - The Oxford Companion to wine