Grenache is an unlikely hero of a grape. Until recently reviled or at best ignored in much of the world, it is the grape chiefly responsible for two of the world's more celebrated reds, Châteauneuf-du-Pape and, a more recent star, Priorat.

Part of Grenache's problem is that it is so widely planted. Although in this century much of it has been uprooted as part of the EU vine pull scheme, at the end of the last century it was planted on more land than any other grape in the world apart from La Mancha's white Airén grape because, as Garnacha, it was Spain's most common red wine grape. It is widely planted all over the northern half of the country that has more land planted to vines than any other in the world. In both Rioja and Navarra it is regarded as playing a distinctly ignoble second fiddle to Spain's vine speciality Tempranillo. The wine it produces here can be much softer and jammier than the well structured, deeper-coloured Tempranillo, but it doesn't have to be. Provided yields are restricted, and particularly if vines are relatively mature, Garnacha can produce some alluring rich, spicy reds in northern Spain – and there are particular pockets in Rioja Alta upriver of Nájera and in Rioja Baja in the high vineyards of Tudelilla, for instance, where Garnacha vines are renowned for the voluptuous flesh they can bring to a Rioja. The ambitious Roda bodega, for example, values top quality Garnacha as highly as fine Tempranillo.

In Navarra Garnacha has traditionally been used to produce pale wines labelled either rosado or, slightly darker, clarete. Indeed the relatively thin skins of Grenache/Garnacha have persuaded many a winemaker – most notably in Provence – to make a rosé out of this misunderstood grape. But this is only part of the story. A whirlwind tour of many northern Spain wine regions, both famous and obscure, last year convinced me that Garnacha is an under-used resource in many Spanish vineyards.

Perhaps its reputation has been sullied by the red-fleshed version known as Garnacha Tintorera in Spain, and Alicante Bouschet elsewhere (grapes with red flesh are generally regarded as slight cheats). There is also a variant with particularly hairy leaves widely planted in Spain as Garnacha Peluda and in Roussillon and western Languedoc as Lledoner Pelut. It is customary to blend the hairy-leaved and regular versions.

But what has most dramatically revived Garnacha's reputation in Spain is the intense, minerally top wines grown on the schists of Priorat where ancient Garnacha bush vines provide the backbone of many of the greatest wines, Álvaro Palacios’s L’Ermita being a case in point.

As Grenache the vine is planted all over southern France. Just north of the Spanish border in Roussillon it is common in at least three different colours: purple-skinned Grenache Noir, pale crimson-skinned Grenache Gris and green-skinned Grenache Blanc. On the steep terraces overlooking the Mediterranean above the ports of Banyuls and Collioure it can reach extraordinary ripeness levels (a general characteristic of Grenache everywhere) and is the chief ingredient in the sweet, strong vins doux naturels made there. Banyuls is the most famous but further north in Roussillon it produces similar wines such as Maury and Rivesaltes as well as doing its bit to make Roussillon's dry red table wines so strong and ripe-tasting. If there is one single characteristic of Grenache-based wines it is a sweet ripeness, coupled with quite tough tannins if yields are low.

Grenache Blanc makes interesting, if sometimes slightly blowsy, white table wines all over the south of France. They tend to relatively low acidity, high alcohol and fast development, but make a delightful change from the thinner offerings of its traditional blending partner Maccabéo (see Macabeo).

As for Grenache Noir, it is one of the most important red wine grapes of the Languedoc where it has long been blended with Carignan (also underappreciated), Syrah, Mourvèdre and, sometimes, a bit of Cinsault (another grape often used for rosés). Increasingly, however, Grenache/Syrah/Mourvèdre, or GSM, is regarded as the holy trinity in this part of the world. This is the classic blend for the southern Rhône's best red wines: Châteauneuf-du-Pape, Gigondas, Vacqueyras, Lirac, Tavel and a host of increasingly exciting bottlings from Rasteau and Cairanne. The Syrah adds structure and longevity. Difficult-to-ripen Mourvèdre can add an exotic gamey, almost animal note. But Grenache Noir is the grape most at home in the best dry, almost drought-prone vineyards of the southern Rhône.

With its upright growth and strong, sturdy trunk, Grenache is ideally suited to being grown as a water-seeking bush vine in hot, windy areas, its only disadvantage being its predilection to set relatively little fruit. But that, of course, means all the more flavour in the grapes that remain. Some of the finest Châteauneuf of all, that made at Château Rayas, is made from Grenache Noir alone, and although Château de Beaucastel, perhaps even better known, incorporates all 13 of the grape varieties permitted in red Châteauneuf, Grenache and Mourvèdre each constitute about a third of most blends.

The vine is relatively late ripening so can be grown successfully only in quite warm regions. It is particularly important, as Cannonau, in Sardinia where locals claim the variety had its roots before being exported to Spain and France when the island was part of the kingdom of Aragon. Calabria and Sicily also grow some.

In California it is widely planted but chiefly associated with the cheap and cheerful Central Valley and oceans of blush wine. It makes very small quantities of serious wine when pruned severely but doesn't ripen particularly successfully in coastal regions. For some reason the state's Rhône Rangers, wine producers who have turned their backs on Chardonnay and Cabernet to explore the possibilities of such grapes as Syrah, Mourvèdre, Viognier and Roussanne, have virtually ignored Grenache.

In Australia too it took some time for old Grenache vines to earn anything like the respect accorded to old Shiraz and Mataro (Mourvèdre) vines, but each year more and more new bottlings emerge from the Barossa Valley in particular carrying the name Grenache either in splendid isolation or as a fully acknowledged ingredient in a blend with Syrah and Mourvèdre.

Old vine Grenache bottlings are emerging from South Africa and the variety is also grown in Israel and North Africa.

Suggested Grenache-dominated wines include Ch Rayas, Châteauneuf red; Ch de Beaucastel, Hommage à Jacques Perrin, Châteauneuf red; Dom Santa Duc, Gigondas; Dom du Mas Blanc, Banyuls hors d'age de Solera; Dom Gauby, their best Grenache Blanc white wine; L'Ermita, Priorat, Alvaro Palacios; Greenock Creek Grenache, Barossa Valley; and David Grenache, Swartland.