Ernst Loosen is one of the most recognisable global figures in wine. This indefatigable ambassador for Mosel Riesling pops up all over the place to spread the gospel according to this most versatile of grapes. Dr Loosen has managed to pull off something special as a brand and a domaine: quality at scale and a range of grand-cru bottlings that faithfully express some of the planet’s most breathtaking sites without costing the earth. There’s plenty there to admire, but as a fan of German precision, I wanted to put a more practical question to Erni this time.

Erni has been at the helm of the Dr Loosen estate in Bernkastel since the late 1980s. In his time in charge, he has revived lesser-known, ancient German customs by “innovating” with patiently raised, balanced dry wines while respecting the valley’s traditions with precisely delineated off-dry to lusciously sweet styles. When you take into account that Dr Loosen makes single-site wines from 11 grands crus spread across several villages and encompassing all Prädikats, the logistics get quickly complicated. I just wanted to know: Come vintage time, how the heck does he marshal his pickers to get it all done?

What follows is the preamble to the podcast, so if you listen to that, you needn’t read this (although it may help familiarise you with place and category names). Similarly, the video below is the interview segment of the podcast, so if you’re reading this, watch that and ignore the podcast. Got it?!

The Mosel Valley is in Germany’s west. It’s named after the Mosel River, which rises as the Moselle in the Vosges mountains in France. In Germany, it twists its way up to join the Rhine River at Koblenz. The Upper Mosel, or Obermosel, crosses the border into Germany and winds its way up to the city of Trier. Around here, you have the famous tributaries of the Saar and Ruwer, both of which are home to famous producers and distinctive wines; this area is referenced in my podcast with Cornelius Dönnhoff and Philipp Wittmann.

At the opposite end, at the river’s northern tip, you have the Untermosel, or Terrassenmosel, known for its towering stone terraces. This is where you’ll find Heymann-Löwenstein, in honour of whose renegade founder, Reinhard Löwenstein, I penned this tribute. And in between, you have the Mittelmosel, or Middle Mosel. Here, you will find Weingut Dr Loosen and its famous sites.

Erni has grand-cru vineyards—the German is Grosse Lagen—in several villages. Travelling downriver, these are Bernkastel, Graach, Wehlen, Ürzig, Erden, Lösnich, Kinheim and Bremm. Using the German convention of adjectivising the place name and prefixing it to the vineyard name, the Grosse Lagen are Bernkasteler Lay, Bernkasteler Johannisbrünchen, Graacher Himmelreich, Graacher Domprobst, Wehlener Sonnenuhr, Ürziger Würzgarten, Erdener Prälat, Erdener Treppchen, Lösnicher Försterlay, Kinheimer Rosenberg and Bremmer Calmont.

The Mosel is Germany’s oldest winegrowing region, with the Romans bringing vines here 2000 years ago. In 1787, the Archbishop of Trier decreed that Riesling replace all inferior vines in the valley. A century later, Germany’s Riesling wines were the most revered and sought-after on the planet. All kinds of things went pear-shaped for Germany in the 20th century, and it also shot itself in the foot with wine laws that undermined the primacy of good farming and the supremacy of Riesling and other quality grapes. These days, Riesling is back where it belongs: No. 1 in Germany. It accounts for just over 62% of the Mosel vineyard.

Mosel Riesling is the world’s most distinctive rendition of this grape, and that distinctiveness is borne of hugely specific circumstances, to which the river valley is key. This is a cool, continental climate at high European latitudes. That makes it marginal for ripening Riesling grapes (please refer to my interview with Jason Lett of The Eyrie Vineyards in Oregon for a fantastic explanation of marginality). Though relatively cool, summer days are long, with, hopefully, plenty of sunlight bringing intense, bright flavours to the grapes, which—though they achieve relatively low sugar and therefore potential alcohol levels—hang on the vine for a long time, developing surprising depth.

Because water cools more slowly than land, the river helps extend the growing season by delaying the onset of properly cold weather. It also reflects light onto the photosynthesising vines. On the river’s banks, the vines climb steep slopes, ideal for intercepting more light. As you drive up the valley, it’s obvious that most of the planted slopes share the same orientation, facing predominantly south for maximum sunshine in the northern hemisphere.

The soils are mostly slate, although Ürziger Würzgarten is extremely rare with its red volcanic rock. These extremely stony soils retain and reradiate heat. This exceptional set of circumstances combines to ensure slow but complete ripeness in a cool place where acidity will naturally be high and grape sugars comparatively low.

The steep, stony slopes are not conducive to machinery, and hand-harvesting is a key Mosel custom that Erni and I discuss: grape selection for different wine styles. Another factor giving rise to strict selection is botrytis cinerea, or noble rot. Humidity from the river gives rise to misty autumn mornings, when the fungus begins to attack the grapes, puncturing the skins and causing water loss, thus concentrating flavours, sugars and acids. So long as the grapes stay otherwise healthy, with warm, stable afternoons to dry them out, this can reap benefits and is the key to nobly sweet wines such as Tokaji and Sauternes.

This brings us to the point of this interview. The Mosel Valley is the wine region that most fully exploits the full Prädikat spectrum. So called because the style of wine is predicated on a minimum must weight—that is to say, the amount of sugar in the must at the time of harvest, measured in degrees Oechsle—the Prädikat system spans six categories. Starting with the lightest style, Kabinett, the other five Prädikats, in ascending order of minimum must weight, are Spätlese, Auslese, Eiswein, Beerenauslese (BA for short), and Trockenbeerenauslese (TBA).

Kabinett, Spätlese and Auslese can all be dry; therefore, the amount of alcohol and residual sweetness in these wines varies according to the winemaker’s aims. When Erni talks about declassifying fruit, he means that grapes that qualify for Spätlese and above automatically meet the minimum must weight for Kabinett. In the Mosel, you have the option to “declassify” these grapes to the “lower” category of Kabinett, but Erni explains that this would do a disservice to the category and the customer. (Incidentally, his anecdote about the Vinea Wachau, where declassification is outlawed, involves Emmerich Knoll, who crops up in this Austrian Riesling piece).

Beerenauslese and Eiswein have the same minimum must weight and are always sweet; the former relies on botrytis to concentrate its sugars, the latter is harvested when fully frozen. This removes water from the equation during pressing, yielding extremely high must weights. Highly rare, expensive Trockenbeerenauslese is made from the highest-quality, totally shivelled, botrytised berries.

The other style we talk about is the GGs, or Grosses Gewächs wines. A GG is the top dry wine from a grand-cru vineyard (Grosse Lage) by a member of the VDP. Dr Loosen, Wittmann, Dönnhoff and Gunderloch are all members of this private band of quality-focused growers. Again, there is more context on this in my interviews with Cornelius, Philipp and Johannes Hasselbach of Gunderloch. In the six-minute video embedded above, Erni talks about the terroir of three of his GGs: Wehlener Sonnenuhr, Ürziger Würzgarten and Erdener Treppchen. It’s highly illuminating and not as dry as it sounds, I promise.

Finally, Erni mentions some of the estate’s wine-growing preferences here, such as excluding botrytis-affected grapes from the Kabinett and GG wines. The estate’s Kabinett and Spätlese wines always have residual sweetness (as a rough guide, usually just above 40g/L of residual grape sugar for the Kabinett and 60-ish for the Spätlese). The Auslese wines comprise roughly 50% healthy and 50% botrytised berries and come in with roughly 90g/L residual sugar. Remember, though, that such wines have extremely high acidity to balance this.

If it isn’t already obvious, Erni is something of a maverick, and he produces a couple of sub-genres of GG that sort of shouldn’t exist. These are dry grand-cru wines with extra ageing in barrel and bottle before release, and they’re labelled GG Réserve and GG Homage.

I’d like to extend my thanks to Erni Loosen for the generosity with which he has always shared his time and wisdom, and to the Dr Loosen team, who were responsible for most of the superb images on the video version of this podcast.

This is a public episode. If you'd like to discuss this with other subscribers or get access to bonus episodes, visit edmerrison.substack.com/subscribe