Riesling in the vineyard
Bestowed by nature with hard wood to sustain cold winters Riesling rests longer during the winter than most other varieties and buds rather late in season. It knows that in a cool climate the winter can always make a surprise comeback in the form of late spring frosts, one of the biggest hazards for grape vines and budding later in the season minimizes the risk. Always wary of unpredictable weather Riesling is usually also one of the last varieties to flower in the vineyard. Patience is one of its many virtues.
Even if spring frost is less of a danger for Riesling's tough and fibrous body, it demands a site sheltered from cold winds, often on steep hills that provide maximum exposure to sun. Even on the most sheltered site Riesling is not an easy grape variety to grow. It's tight bunches of small berries are prone to rot during periods of rain. Coulure, the failure of the vine's flowers to turn into berries, can also be a problem for Riesling. It is also prone to millerandage, which causes the growth of differently sized grapes on the same bunch where the smaller grapes have no seeds. Although millerandage means reduced yields, some growers actually welcome this disease as the seedless and small grapes are considered to be of superior quality.
And then there is botrytis cinerea, a fungus that can grow on grapes after periods of rain. Botrytis, also called noble rot (or Edelfäule in German), punctures the skin of the grapes and causes some of the water in the berries to evaporate. With the loss of water the flavor components and sugars become heavily concentrated in the berries. Some of the most heavenly sweet wines are made from botrytized grapes.
If conditions in the vineyard are conducive magic things are happening in the small grapes. Riesling feels most comfortable at moderate temperatures, ripening its fruit without haste or urgency during the longer hours of daylight that the cool northern climates provide. During the slow ripening process high levels of extract are accumulated: sugars, acids, minerals, phenolics and glycerol.
Riesling likes to be left alone, in the vineyard as well as in the winery. On impossibly steep vineyards in Germany's Mosel region and sometimes in plots hardly accessible by human beings, Riesling bonds with its solitude and willingly picks up the character of its place. More than any other grape variety Riesling speaks of where it was grown.
It prefers poor soils (like all grape vines), forcing its roots to grow deep into the ground. In Austria Riesling is planted in primary rock and slate soils (whereas the vineyards with nutrient-rich soils such as loess and loam are usually planted with Grüner Veltliner). Slate is also dominant in Germany's Mosel region. Slates warms up during the day and radiates heat back to the vine at night. Slate also drains quickly, which is important because vines don't like wet feet. Alsace's sandstone and schist soils are equally poor in nutrients but at the same time they are rich in minerals.
Riesling can be vigorous. Yet even at a yield of 60-70 hl/ha the quality of the wine can be outstanding. Nevertheless, quality-minded producers keep their yields much lower than that, often at around 20 hl/ha.
In Alsace, where Riesling vineyards lie next to those of Gewurztraminer, Pinot Gris or Pinot Noir, it is always the last variety to be picked. Its harvest marks the end of a long growing season fraught with peril. However, in wine regions with cold winters producers may leave healthy berries on the vine until the first frost in order to produce icewine from grapes naturally frozen on the vine.
Blue slate soil in the Mosel