Terroir and soil type in regional Riesling varieties

Rieslings

A Drink for All Ages

There are three kinds of wine, those that are most rewarding when drunk in their infancy and those are suitable to be drunk after they have aged, and those that can be drunk either young or old. Riesling is one of these latter: Usually drunk young, it does improve (and change) with age. While many of the best Rieslings are still made from grapes grown in the wine's origination country of Germany, it is now grown in a number of different regions around the world. As is true for every type of wine, the terroir matters for Riesling. While some wines are very hard to distinguish in terms of where they were cultivated, this is never true of Riesling.

The concept of terroir is complex and difficult to convey in words alone. The following, however, encompasses much of what is meant by the term:

I define a "vin du terroir" as a wine with vineyard specific, inimitable characteristics, the nature of which can not be explained by an array of unambiguous measures, and where the winemaker is subordinate relative to the terroir. (The geology of the vineyards of Alsace, 2008)

Indeed, the terroir for Riesling is especially important, and this is the focus of this paper. This paper provides an assessment of a range of varietals to determine what the key features are in determining the most significant factors that differentiate the various varietals. Among these features are the types of soil, climate variations, and style of viticulture. Of these three major influences on the quality and taste of wine, soil type is probably the most important. Soil is such a strong determinant of the quality of grapes and thus of wines in large measure because grape roots extend so far down -- extending down 30 yards at times to supply a steady and sufficient source of both water and nutrients to the plants (Linhoff, n.d.) Riesling grapes are especially sensitive to the range of soil type variation that the roots encounter as they descend from surface to bedrock, as Linhoff (2005) describes:

… wine growers are concerned with the entire soil profile from the surface to the bedrock. Significant changes at any depth can affect grape vines. Furthermore, soil makeup directly influences many aspects important in quality grape growth. One of these aspects is the acidity of soil. Soil acidity has a direct influence on nutrient uptake and is therefore of great importance to grape growers. (p. 46)

Because of its importance of soil type on the quality of vines and grapes, it will be the primary focus of the analysis of three regional varietals of Rieslings.

Good Rieslings are quite widely available at reasonable prices, which means that they are often the choice of individuals who know relatively little about wine. As a result, there has grown up a mini-industry helping to explain to the novice wine aficionado how regional differences should be considered when selecting a Riesling that meets the needs and preferences of each individual.

Riesling Provenance and History

Before examining the differences among selected varietals of Rieslings, I will provide an overview of what is common to all members of this wine group. Rieslings, which are generally considered to be among the top three most important white wines (along with Chardonnay and Sauvignon Blanc) have a long history in Europe. The majority of Riesling grapes are grown in Germany, although Australia, Austria, the Czech Republic, France, Italy, Luxembourg, and the United States all grow the white Riesling grapes on a commercial level. Rieslings prefer a cooler climate, and so are not grown in a uniform fashion across the countries where they are cultivated. The fact that Riesling grapes can only successfully be cultivated in colder climates is of increasing concern as climate change affects more and more of the Riesling-growing regions of the world. (Of course this is true of other wines as well.)

The conventional assignment of parentage for Rieslings had been that it is descended from wild grapes that grew in the Rhine Valley, but newer examination of this wine grape (using the process of DNA tracking) has documented the fact that one of the key ancestral plants of Riesling grapes is the Gouais Blanc variety. Gouais has an even longer history than Riesling, having been planted across a wide swath of France throughout the Middle Ages (Robinson, 2006, p. 319). It was considered a somewhat inferior wine, the grapes for which were planted in areas only when the micro-climate could not support the more highly prestigious Pinot Noir or Pinot Gris. Gouais Blanc produced an acidic wine that was considered to be overly simple for sophisticated and cultivated taste. While the Pinot wines were drunk by the nobility and members of the clergy, Gouais Blanc was the choice of ordinary workers and farmers (Robinson, 2006, p. 319).

Gouais Blanc (called Weisser Heunisch in German) was extensively cultivated during the Middle Ages in both France and Germany, although it is now rarely seen. It is no longer cultivated commercially and is in fact difficult to find at all. The other documented parentage (again, through the process of DNA analysis) of Riesling is a cross-fertilization that includes both Heunisch and Traminer varieties. Since these latter two varieties are most common in Germany, the assumption that Riesling did in fact originate in Germany is certainly arguable, although it is also possible that the variety was first cultivated in France (Bird, 2005, pp. 95-7). There have been enough exchanges of genetic material among different wine traditions that it is now impossible to untangle with absolute confidence and exactitude the ancestry of modern varietals of wine. This may actually be a good thing: A little mystery is not a bad thing at all in the consumption and appreciation of wine.

Common Elements of Rieslings

In general, as noted above, Rieslings from throughout the world can vary widely in their taste. However, there are common elements to the range of tastes and aromas. Rieslings are generally fruity when drunk young (which is more often than not). Different assessments by educated wine tasters of Rieslings suggest that it has the fruit flavors of apples, peaches, and grapefruit along with other aromas including honey or roses (Bird, 2005, p. 93). Aged Rieslings are often considered to have petroleum overtones.

The fact that Rieslings have a high degree of acidity qualifies them as a wine that can be aged successfully. That is, the level of acidity is adequate for the chemistry of the wine to remain stable over a long period of time; this stability is what ensures that the wine will remain drinkable over decades and even potentially centuries. The standard range of aging times for different Rieslings is as follows: Five to fifteen years for dry Rieslings; ten to twenty years for semi-sweet Rieslings; and between ten and thirty years for sweet Rieslings (Robinson, 2006, p. 736).

German Rieslings

The home of the Riesling historically is the Rhine Valley, and Germany remains one of the most productive regions of the world in terms of the number of different types of Rieslings and in terms of the number of prestigious Rieslings. The prestige of the wines from this region arises both from their objective quality (to the extent that wine can be said to be able to be judged objectively) and from the fact that some connoisseurs believe that there is something more authentic about Rieslings from their home region.

As Asimov (2010) describes it: "a good German riesling from the Mosel region is like no other riesling in the world. It is simply one of wine's singular glories." Asimov (2010) continues his exegesis of the glories of Mosel Riesling, especially the varieties that are made with grapes that have been allowed to stay the longest on the vine:

In my ideal world, the wine in the glass I raise each year to the coming of spring is a Mosel kabinett riesling. It is a wine of gorgeous delicacy, as fragile as the petals on those first tentative blossoms yet possessing a tensile strength that comes of perfect balance. It is a captured moment, evocative more than impressive, fleeting rather than penetrating, whispered nuance, not high volume.

The above language demonstrates the usually floridness of the wine review (and there is as well the temptation that is always present when reading a wine review to assume a certain degree of required hyperbole). But it does suggest the subtleness and simplicity of the best German Rieslings.

Riesling grape cultivation completely dominates the Mosel Valley:

Mosel is fifth among the thirteen German wine regions with respect to both vineyard acreage and total wine production. ...

More than half of all Mosel wine is Riesling. The German hybrid Mueller-Thurgau represents about 20% of the wine production. In third place is the historic variety Elbing that dates back to Roman times and is the major grape variety in the neighboring country of Luxembourg. Only about 2% of Mosel wine is red. (A Mosel Riesling, 2011)

The region in which German Riesling grapes are grown is centered on the valleys of the Mosel River, especially along two of the Mosel tributaries, the Ruwer and the Saar. These valleys are far from rolling: The valleys along the Mosel are steep, so much so that they might seem (if they were not already planted with vines) to seem too steep to support viticulture. These hillsides are also relatively steep, which is one of the most important elements in what makes German Rieslings acquire their specific identity. The higher altitude at which the grapes are grown translates into a cooler microclimate for the grapes, which lengthens the period that it takes for the grapes to ripen. This is one of the fundamentals of German Rieslings (Dawson & Molesworth, 2011).

The soil type in the Mosel Valley also affects the taste of the Rieslings produced from the region's grapes. The soil combines several types of slate (including a range of colors from red to blue that incorporate subtle but important chemical differences that get played out in the final taste of the wine). Both the steepness of the hills and the slate-based soil contribute to Rieslings that are considered to be among the purest of the wine variety.

The Mosel Valley has long been considered one of the world's most beautiful river valleys. This region, formerly known as Mosel-Saar-Ruwer in honor of its three rivers, is proud of its Riesling wine.

Some of the greatest Rieslings in Germany and in fact in the entire world come from the Mosel Valley. Experts can often identify Mosel Rieslings because of the slate in the local soil, which may impart a taste of flint. Mosel vineyard slopes are among the steepest in the wine-producing world.

They sometimes attain a whopping 70 degrees. The soil is so precious that every spring local workers lug pails of soil up these slopes. This arduous activity temporarily reverses the effect of the rains that wash the soil down every winter. (A Mosel Riesling, 2011)

Mosel Valley Rieslings are also especially marked by the fact that they are slightly sweeter than Rieslings from other parts of the world. The higher sugar content of Mosel Rieslings balances out the high acidity of the varietals from this region, and this balance of sweet and acidic is highly characteristic of Mosel Rieslings (Slinkard, n.d.)

Finger Lakes Rieslings

Wine regions tend to be dedicated either to red or white grapes, although there are of course some regions that mix both. A highly unusual viticultural strategy is to shift from being primarily red to primarily white (or the reverse). But this is close to what has happened in the Finger Lakes wine country, which was until quite recently known only for its production of red wine grapes. However, in the last decade, it has also become the home to a number of Riesling wineries. This is true despite the fact that the region is certainly not the typical Riesling climate and is profoundly different from the ancestral German climate of the oldest Rieslings.

The difficult climate, combined with a diverse combination of soils, makes the Finger Lakes one of the most unusual American wine regions. In the last decade or so, it has begun to show its enormous potential, as a small but growing number of producers makes graceful wines that stand in contrast to prevailing styles from the West Coast. (Asimov, 2011).

The "difficult" climate -- difficult for wine production, that is -- is directly related to the nature of the lakes.

This should hardly be surprising given that the lakes are the most single important environmental and ecological feature of the region. As Asimov (2011) describes the importance of the lakes for viticulture: "The lakes, deep claw marks left in the earth of west-central New York by glaciers moving south from the Hudson Bay, are as much a part of the winemaking culture here as tough vintages like 2001."

Both soil type and climate are central in determining the distinctive features of the Finger Lakes Rieslings. The most important climatological feature is that the significant depth of the lakes serves as a stabilizing force on temperature, a force that "nudges this otherwise inhospitable region to a level of bare tolerance for the fine wine grapes planted on the lakes' slopes" (Asimov, 2011). The depths of the lakes prevents them from freezing in all but the coldest winters, creating a protective micro-climate for the dormant vines that thus avoid frost damage. The estival climate, also guarantees the health of the grapes by providing a cool temperature that envelops the vineyards and prevents too-quick ripening.

Cass & Robinson (2000) note that the Finger Lakes wine country climate "differs amongst the regions based on the Atlantic Gulf Stream and the numerous bodies of water and mountainous regions around the state" (p. 130). Key among these differences is the range of annual precipitation, which ranges from 30 inches to 50 inches in different micro-climates. This, in turn, supports a Finger Lakes grape wine growing season of 180 to 200 days a year,.

The composition of the soils of the Finger Lakes wine country has been most significantly influenced by their origination in the last glacial advance in the region. The wine regions' soils originated from the last glacial advance which left gravel and shale type soils with heavy clay deposits in the Finger Lakes region (Cass & Robinson, 2000, p. 128). More than is the case in the German Riesling-production areas, the Finger Lakes Riesling country is divided into numerous micro-climates (even arguably micro-micro climates). In addition to variations in precipitation, small variations in soil type (and specifically in soil acidity) that occur even across a very short distance produce significant results in the quality of the wine.

The following, somewhat technical description of soil variation explains why adjoining vineyards produce wines of differing quality and tastes:

Vineyards with calcareous limestone bedrock require little or no lime addition for pH correction despite the low pH of regional acid rain. In contrast, very heavy lime addition is required in vineyards located over noncalcareous bedrock. The high lime requirements in these vineyards are the result of both low rain water acidity and high clay content. Calcium carbonate transport through clay rich soils is inefficient and slow therefore requiring higher amounts of lime addition to the soil. (Linhoff, 2005)

The average Riesling drinker can hardly be expected to be aware of how the structural differences in soil can make significant differences in the way in which the wine in their glasses tastes. However, if soil type and acidity are not exactly destiny when it comes to the production of world-class Rieslings, they are key. This does not mean that soil type is not fungible. As the above citation suggests, soil can be amended.

Amending soil is a practice that is nearly universal throughout agricultural practices, although the amendment used is usually something other than lime. But it is important to note that viticulturalists can use the latest knowledge about soil chemistry to shift that chemistry toward the process of directing their grapes in the direction that they want their Rieslings to go. Manipulating soil content has not been the most important of the options available to winemakers seeking more control over their product, but it has become increasingly important as new techniques of soil emendation have become available.

Finger Lakes Rieslings are generally toward the dry end of the range for this wine, a trend that is a part of the overall sophistication of Rieslings from this region that seek to "maximize varietal character by harvesting at levels which are not likely to make for an excessively ripe flavor" (Berger, 2007). He goes on to describe key elements of Finger Lakes Rieslings as being "a certain mild citrus and Granny Smith apple character in their aroma with a mineral-y base and some muscularity."

There is a range of sugar levels in Finger Lakes Riesling, and a number of the Rieslings from this area of New York have "been fermented with a yeast strain that accentuates terpenes" that give the wines floral overtones and tropical fruit aspects. The yeasts contribute to an "exotic aroma" in regional Riesling (Berger, 2007). The range of Riesling types that are being produced in New York are substantially narrower than is the case in Germany. This is hardly surprising for several reasons.

Conclusion: How these Three Regional Rieslings Compare

The Riesling industry (using this term in a loose sense) is much younger in New York than in Germany and so it is hardly surprising that it should exist within a relatively narrow range as of yet. The second reason is that the range of soil types is smaller in New York than in Germany, which limits the range of Rieslings that can be produced. This is related to the fact that the geographic range of wine-producing land is smaller in the Finger Lakes region than in the Mosel Valley.

The Rieslings that are produced in New York thus do not extend as far into the sweet end of the range as is true of those produced in Germany. This does not mean that the Rieslings produced in New York are any less distinctive than are those produced in Germany. The yeasty flavor described above is highly distinctive, as is the somewhat more complex mixture of notes in the aroma of the New York Rieslings.

While the range of Rieslings produced in New York is narrower than that produced in Germany, the range of Rieslings produced in Alsace is arguably greater. It might seem that there would be an objective way of determining the range of Rieslings in each of these regions, but in fact this is not the case. As noted above, there is very little that is objective in the world of wines. Certainly one can tally the number of appellations, but this is only one measure.

The complexity of the geology in Alsace produces micro-variations among not only different vintners but among different vintages and even different bottling. These are subtle variations, smaller than the variations that generally occur between Mosel bottling, sufficiently subtle that some might not consider them to be sufficient to count as different tastes at all.

There is also the fact that while Finger Lakes Rieslings are predominately dry (although closer to the sweet end of dry than the extremely dry end) and Alsatian Rieslings are predominantly sweet, Mosel Rieslings run the entire range of dry to sweet. In assessing the range and quality of the Rieslings from each of these three regions, each person must decide on which qualities of the wine are most important. These include both the taste and aroma of the wine as well as other aspects of it that can be equally important. For those who value what might be called purity of ancestry, the Mosel wines must win out.

For those who are interested in an attitude that allows more latitude to the wine and less control by the vintner, then the Alsatian wines must win out. And to those who value an up-and-coming experimental region for Rieslings, the Finger Lake wines would be the best choice.