‘When just released they’re vibrant and fresh,’ says James Fox, winemaker at Rockford Wines. ‘Then they go in the closet for two to three years,’ he continues, referring to a closed period when the wines are less expressive. Barossa Shiraz can be muscular but tannins are rarely hard or angular even when young. This friendly, approachable nature means drinking early is an option.

While there’s wild, hedonistic pleasure to be had, the best drinking is yet to come. At around 10 to 12 years of age, they start to take on real complexity. The fruit is still plush and juicy, and the oak is better integrated, weaving smoke and spice through the wine in a more harmonious way. ‘10 to 15 years is ideal,’ says Fox.

At around 20 years you can expect forest floor notes, often interwoven with spices like star anise, cigar tobacco and black olive – umami characters start to emerge. ‘They plateau at 20 then enter a lovely holding pattern,’ says Ian Hongell, winemaker at Torbreck (lead image); they become ‘like a time capsule.’ The best examples retain freshness, energy and salinity as they reach this point; less balanced examples start to wobble, with any excess acid, oak or alcohol showing through. Their overall trajectory depends on numerous factors, including vine age, sub-region, soils, winemaking and vintage.

Barossa Valley is home to the oldest Shiraz vines in the world, dating back to the 1840s. According to Hongell at Torbreck, they have ‘longer, danglier bunches that take longer to ripen,’ and offer ‘a different profile of tannins and expression of fruit.’ This old-vine material contributes to the concentration and intensity of the style. But that’s not the only natural factor benefitting the region’s Shiraz and its longevity.

‘Barossa’s greatest strength is its soils,’ says Brett Hayes of Hayes Family Wines, and the expression of Shiraz is very different depending on where it’s grown. Since 2008, the Barossa Grape and Wines Association has co-ordinated extensive research to examine the various terroirs of the Valley. They have defined three main zones: Northern Grounds, Central Grounds and Southern Grounds.

Many of the best come from the Northern Grounds, which combine power with textural finesse. There are great expressions too from the Central Grounds, often even more concentrated, that develop forest floor aromas with time. I didn’t taste any made from pure Southern Grounds fruit, but according to one winemaker they have a reputation for ‘tightness and tautness’.

Eden Valley, to the east of Barossa Valley, produces a style apart. The higher elevation results in wetter, cooler weather and the soils are shallower, rockier – it’s an altogether wilder landscape. Shiraz from this terroir has more blueberry than blackberry, more silk than velvet. It’s a refined, perfumed style of Shiraz that doesn’t live quite as long but is just as compelling.

Vintage makes a big difference to how long a wine will last. If you’re sourcing Shiraz with a view to cellaring, consider 2021, 2018, 2015, 2012 and 2010. If you’re looking for mature bottles to drink, seek out 2006, 2005, 1999, 1998 and 1996.

According to legendary Barossa winemaker John Duval, when a Barossa Shiraz reaches peak drinking ‘is in the eye of the beholder’. It’s true: some will prefer them young, on the fruit; others in a more venerable state of aged complexity. But I believe if a wine has the capacity to develop and improve over time – and not all wines can – it deserves the opportunity. And, as I witnessed in this tasting, Barossa Shiraz can age beautifully.