Riesling

Physically, Riesling is distinguished by the hardness of its wood, which helps make it a particularly cold-hardy vine, and a great choice for relatively cool climate regions. In California, it is at its best in cooler growing zones, with most plantings concentrated in the Central Coast.  

When it is at its optimum, California Riesling is supremely expressive — exotic and floral, vividly fruity, persistently mineral. At its apogee, Riesling is an intellectually stimulating grape, with a precision and complexity that for many cannot be surpassed. No other variety showcases place and time like Riesling, increasingly so as it gains bottle age. But it can also be very shy (hence the comment of it being intellectual or cerebral). For those seeking immediate pleasure and an outgoing personality, this may not be your grape—the vinous equal of a party wallflower rather than the festive extrovert dancing on the table with a lampshade on his or her head; you need to be focused and patient.

Working The Land:

Does soil influence the flavor of the final wine?

Traditionalists answer unequivocally “Yes!” Soil is a key element of terroir, the natural environment in which the vines grow, along with climate (temperature, rainfall), topography (altitude, drainage, slope, aspect) and sunlight.

A more unorthodox view holds that the influence of soil on what you taste in the glass is a myth. Maynard Amerine and Ann Noble, two famous names at UC Davis, California’s premier wine school and research facility, conducted a study on the topic: though based on Chardonnay, it concluded that the following holds true for all wine grapes: “no outstanding sensory differences were observed in wines produced from different soil type locations.” The key word is “sensory” (sight, smell, taste); they are not saying that the soil doesn’t affect vine behavior (yield, growth cycle, etc.). 

The subject is most certainly up for further debate. That said, here is a brief review of how Riesling, according to the classic view, expresses itself in the glass, based on the type of soil in which it is grown.

Slate Soils

Closely related to, but less compressed than schist, slate is an alluvial deposit formed under heat and pressure. Dark and variable in color, slate is easily broken, but not as subject to weathering as other soils. It both absorbs and reflects heat, helping to ripen grapes. In Germany’s Mosel, it is said that blue slate lends flavors of minerals and green apple, while more iron-rich red slate soils offer flavors of peach and smokiness.

CA Locations: There are no specific regions to call out.

Volcanic Soils

Volcanic soil, particularly basalt, is an extrusive soil formed from cooled, hardened, and weathered lava. While this is a complicated soil, it tends to be fine-grained, drains well, retains and reflects heat, and holds water. Volcanic soil also contains high proportions of iron, resulting in black- or red-colored earth, and is sometimes thought to impart an ashy, rusty taste to wines. Rieslings from volcanic soils tend to give off tropical flavors, redolent of apple, mango and papaya.

CA locations: Napa (Atlas Peak, Howell Mountain, Spring Mountain, Diamond Mountain), Sonoma, Lake County (Red Hills, High Valley)

Sandy Soils

Sandy soils generally bring out Riesling’s elegance and aromatics. They are also well-drained and retain heat

CA locations: Contra Costa’s Oakley, southwest Santa Maria Valley, parts of Santa Barbara and Santa Ynez, Lodi

For more information on Riesling and differing soil types, read Master Sommelier Fernando Beteta’s blog post on “Terroir and Aromas of Riesling Based on Soil.”

Well-made Riesling is like a window into the vineyard, reflecting clearly where and how it has been grown. Many experts concur that Riesling best expresses the notion of terroir, which considers the holistic influence of the environment on the vine (soil structure, topography, sunlight, water), as well as the human interaction with this environment. Though it may sound strange, Riesling has a distinct transparency about it.

Most California Riesling clonal selections come from Germany; France and the United States are the source of comparatively few Riesling selections. Although 38 different clones of Riesling are registered with FPMS (Foundation Plant Materials Service) and UC Davis, most growers focus in on just a handful: FPMS 2, sourced from the Geisenheim Grape Breeding Institute, has lower crop yields, equating to wines of elegant fruitiness and pronounced flavor, with all components in good balance. FPMS 3 and 9 (non-certified) are also sourced from Geisenheim and are extremely fruity, but known to display a slight Muscat flavor in warmer sites, not regarded as classic in Riesling wines. Then there are FPMS 4, from an unknown source, FPMS 10, a selection from the Martini family’s Monte Rosso vineyard in Sonoma County, and FPMS 12 from Neustadt, Germany, where it’s known as Clone 90.

Vine training and trellising is mixed and has evolved over the years. Riesling was traditionally head-trained and cane-pruned, due to the grape’s small cluster size. Where bud fruitfulness is low, cane pruning may still be the best option for higher production. Most vineyards today use the vertical-shoot-positioned (VSP) trellis system. There is some interest in the Smart-Dyson system too, although it is probably more suited to high-vigor sites. Riesling is well-suited to machine harvesting, due to fairly thick skins, small berries and easy detachment from the rachis (the skeleton of branched stems which gives a grape bunch or cluster its shape). Moreover, hand picking is quite costly, due to the small berry size. Depending on the extent of botrytis infection and winemaker desire, a combination of hand and machine harvest may be required. 

For more on the Scott-Henry and Smart-Dyson methods, visit “The Scott Henry Training System; Easy to Learn, And a Route to Improved Profitability & Wine Quality” on The Grapevine Magazine.