One of my tutors on the WSET Level 3 summarised students' appreciation of Riesling: "When you study Level 1, you just don't get Riesling. At Level 2, you realise it's important but you don't understand why. By Level 3, you begin to appreciate it more but still don't quite understand why everyone goes on about it. It's only when you study the Diploma that you realise it produces the greatest white wines of the world." Likewise, the Oxford Companion to Wine describes Alsace Riesling as "one of the most difficult varieties for beginners, but one of the most rewarding wines for connoisseurs."

This may seem a snobby, off-putting way of viewing wine - 'you can only appreciate it if you know what you're talking about' - but Riesling does not have the broad appeal of Sauvignon Blanc or Chardonnay. Its flavours are varied and complex, it develops difficult petrol-like aromas as it matures, it's a demanding grape at its best in cool-climate areas, and it's difficult to grow well and economically. Riesling is not so much a drink for connossieurs, but it is one for those - both winemakers and drinkers - willing to dedicate some time and effort to it.

It's also suffered from the whims of fashion. The popularity of Blue Nun and other low-quality German wines in the 1970s and 80s caused the reputation of both German wine and Riesling to fall, even though many of those wines were made from Müller-Thurgau. It's taken a very different style of Riesling from Australia to help regain the grape's reputation.

where it's grown

Riesling's heartland is in the cool areas of Germany around the great Rhine and Mosel rivers. The vines grow on slopes that steeply rise from the river on difficult soils. Particularly in the cool climate of the Mosel, Riesling has to work incredibly hard, which is why the wines are so austere with high acidity. Riesling is also one of the 'noble' grapes in neighbouring Alsace, the only area of France where the grape is able to be grown. The wines are lightly floral when young, gaining a gunflint complexity as they mature.

Despite Australia's reputation as a blisteringly hot country making big, fruity wines, it has gained standing for its Rieslings. In the high altitude areas of Clare Valley and Eden Valley near Adelaide, the wines are fruitier (zesty limes) and more giving than their Alsatian and German counterparts. It is these bone-dry Rieslings, with characteristically high acidity, which have turned drinkers back on to the grape.

styles

The great Rieslings of Germany are known for their sweetness. The regulations and terminology of German winemaking are convoluted and labyrinthine, and it can be difficult to know what level of sweetness to expect. However, the lower the alcohol (and it can be as low as 7-8%), the sweeter the wine. As sweet German wines have fallen out of fashion, more producers are making dry Rieslings (labelled "Trocken") to follow the popularity of Australian wines. Alsace, on the other hand, has always made bone-dry Riesling.

wines

I conducted a blind tasting of three Rieslings, from the Mosel, Alsace, and Napa, an area certainly not known for its Riesling.

Trefethen Dry Riesling 2013 ($25)

The US in general has yet to master Riesling. It is the second most-planted white grape in Washington State, where Chateau Ste Michelle is the world's biggest producer of Riesling, but the wines lack depth and complexity. Oregon, cool and rainy, ought to have the potential to produce interesting Riesling, but producers stick to Pinot Noir - only 718 acres of the grape are planted (compared to over 15,000 acres of Pinot Noir). If you can, try Chehalem's Rieslings. Finger Lakes in New York is cool enough for Riesling, although the wines are still too expensive for what they are. A good example of Finger Lakes Riesling is the Tierce Dry Riesling, made by three of the area's top producers.

California, meanwhile, is just too hot and sunny, but there are a small band of producers that battle through regardless. The cool hills of Santa Rita offer potential for the grape, but only a handful of producers dare tackle it in Napa and Sonoma; in my tastings, I've only encountered Riesling from three producers - Scribe, Chateau Montelena, and Trefethen. In The Wines of the Napa Valley, Larry Walker describes Trefethen's Riesling as "consistently at the head of the class for California," although that's a very small class. Dry, with green apples and a lemon and lime zest, the wine has a nice acidity and the characteristics of Riesling. It lacks complexity, however, its flavours pleasing but somewhat one-dimensional, demonstrating the difficulties winemakers in California have in making truly memorable wine from the grape.

S. A. Prüm Graacher Domprost Estate Bottled 2009 ($31)

From a famous vineyard on the steep slate slopes of the Middle Mosel, this is a superb example of Riesling at its most complex, although not quite as sweet as the classic style of Mosel wine. A wet, farmyard nose with orange peel and apricots, spicy butterscotch, and a whiff of petrol, the wine is maturing nicely at five years of age. Despite that age, the acidity on the palate still gives the wine plenty of structure. The fruits on the palate are a little fresher and more citrus-based than the nose, suggesting that the wine has a few years left yet, and the long finish has a slightly sweet, cinnamon, and white pepper feel. An outstanding wine at an astonishing price, from San Francisco's Ferry Plaza Wine Merchants.

Domaine Ostertag Heissenberg Alsace AOC Riesling 2011 ($36)

Ostertag are one of my favourite producers. Biodynamic, the wines are of a guaranteed quality but also individuality. Slightly younger than its German counterpart but from rich, mineral soils, this Riesling still has a developing, petrol nose with strong orange-citrus flavours. Floral too, with a dry, spicy finish. The rich flavours of the wine make it an ideal accompaniment to an oily, acidic dish such as salmon. As good a wine as this is, however, it lacks the long complexity of the Mosel.

No surprises that the Napa Riesling could not compete with Alsace or the Mosel. I was surprised, however, by how much quality was packed into the latter wine at the $30 mark. The Mosel, with its steep slopes and small vineyards, is a difficult area in which to make quality wine, yet this wine was a complex, sophisticated wine at a very reasonable price. Proof that the best wines of Germany are not always at an off-putting price and evidence of the quality German wine often reaches.