For a long time Tempranillo was ignored by the outside world as a slightly rustic northern Spanish grape of strictly local appeal. It was in the mid 1990s when I was granted my one and only audience with the Gallos in northern California that I realised the grape was now of international interest. Almost as soon as I had sunk into the crimson velour depths of the company limo I was interrogated about my thoughts on Tempranillo. Clearly the world's biggest wine company had it in their sights.

Tempranillo is best known as the dominant grape of red rioja, Spain's most famous wine. To make a parallel with the most celebrated blended red wine in the world, red bordeaux, Tempranillo plays the Cabernet Sauvignon part while the much juicier, fruitier Garnacha (known in France as Grenache) plays the role of plumper blending partner Merlot. Tempranillo provides the framework and ageing ability, together with the predominant flavour, while Garnacha adds weight. Mazuelo (Carignan) and the much finer Graciano (Morrastel) are also allowed in a Rioja blend.

Until the 1990s most red rioja tasted more of oak than grapes. The traditional way of making rioja – ageing for years and years in small, vanilla-scented American oak barrels – disguised Tempranillo's own flavour. But since bodegas in Rioja have seriously begun to age their wines for much shorter periods in French oak, and also to export young (Joven) unoaked wines, wine lovers the world over have started to come to grips with the essence of Tempranillo itself.

The flavour of Tempranillo is essentially savoury rather than sweet. The characteristic smell has hints of leather but the phrase I use most often to describe it is 'fresh tobacco leaves' – even though, as is so often the case with these useful 'trigger words', I am not at all sure I have ever actually smelt fresh tobacco leaves themselves. There is something sappy, fresh and vegetal about it, but also something definitively masculine, the sort of smells you would expect to find in a stereotypical gentleman's dressing room – which is, I suppose, where the leather comes in.

Tempranillo's skins are not especially thick, so the wine is not marked by particularly deep colour, and rot can be a problem, especially in the tight bunches of the newer clones (although compared to most internationally known grape varieties there are not that many clones of Tempranillo available).

The vine has traditionally been cultivated en vaso, as little low bush vines dotting the Spanish landscape, although some growers have been training it up a trellis to increase yields. What is sure is that when the right clone of Tempranillo is grown in the right spot without excessive yields and with real care, then it can produce extremely long-lived wines. I have had the pleasure of tasting late 19th century and early 20th century riojas from the likes of Marqués de Riscal and they are stunning wines on any level. Throughout northern Spain, Tempranillo's stronghold, vine-growing today tends to be in quite different hands from wine-making, which does not always optimise quality unfortunately.

So vital is Tempranillo to other Spanish wine regions that it travels under many local aliases. In Ribera del Duero, the high plateau south-west of Rioja, it is even more important and is known simply as Tinto Fino or Tinto del País. Bordeaux grape varieties and the local Albillo may, technically, be blended with it but rarely are nowadays, except in the region's most famous wine Vega Sicilia which has proved that Tempranillo grown in this extreme climate with its hot days and cool nights can withstand up to 10 years in barrel and still age for decades in bottle. Today there are all manner of young turks and middle-aged fortune hunters trying their hand at making a more modern, concentrated style of Ribera del Duero – all characterised by an intense, deep crimson and, in good examples, a flavour to match. Dane Peter Sisseck has had phenomenal success with his briary cocktail Dominio de Pingus.

In the small, warmer but extremely fashionable Toro wine region to the north, the local, loose-bunched form of Tempranillo is known as Tinta de Toro. So far Toro wine has been made quite simply and is a sort of exuberant, turbo-charged fruity essence of Tempranillo. But sophisticated winemakers have been moving in and we can expect to see more subtle, longer-lived wines emerging.

In Valdepeñas south of Madrid Tempranillo is known as Cencibel and is the predominant red grape, often lightened by blending with the local white Airén. Yields here can be too high for much varietal character to be evident. It is grown all over the Levante and in Manchuela is known as Jancivera. In Catalonia it is important and known in Catalan as Ull de Llebre, Ojo de Liebre in Castilian. In Penedès, as in Navarra north-east of Rioja, its traditional blending partner is Garnacha, but Tempranillo is considered vastly superior. The often antipodean 'flying winemakers' parachuted into Spain to cook up wines for northern European markets have had fun blending Tempranillo with fuller-bodied varieties such as Monastrell (Mourvèdre) and Merlot.

But Tempranillo is increasingly recognised as important over the border in Portugal, both in the north as Tinta Roriz where it is a respected ingredient in port, in the table wines of the Douro Valley and as an improving grape variety in the red wines of Dão, and in the Alentejo in the south where it is known as Aragonês. It is increasingly bottled as a varietal wine, and in the hot climate of the Alentejo in particular can be positively plump.

Elsewhere in Europe, the Languedoc in southern France has long cultivated Tempranillo, even if its produce tends to disappear in blends. The Australians are now becoming rather interested in its novel range of flavours and Brown Brothers of Victoria were the first to sell it in varietal, just-recognisable form. Argentina has grown substantial quantities of the vine they called Tempranilla for decades, presumably since it was imported by Spanish immigrants. Untroubled here by the autumn rains that can plague Rioja, it can produce much riper wines in the right hands. Winemakers such as Susana Balbo at Anubis have applied modern winemaking methods to it to sizzling effect.

Abacela pioneered the variety very successfully in southern Oregon and it is also grown in Washington state. As for California, land of the inquisitive Gallos, growers there have been growing Tempranillo – in small quantities admittedly – all along. The vine known as Valdepeñas is none other than this increasingly confident international traveller.

Specifically recommended examples include Dominio de Pingus, Ribera del Duero; Vega Sicilia, Ribera del Duero; Terreus, Pago de Cueva Baja (Mauro); Paga Negralada, Abadía Retuerta; Roda Cirsion, Rioja; Artadi, Grandes Añadas or Pagos Viejos, Rioja; Finca Allende, Aurus, Rioja; Muga, Torre Muga, Rioja; and Marqués de Riscal, Barón de Chirel, Rioja.