Soil, Slope and Water | April 2018
Many Virginia wineries are now consistently making polished, complex and structured reds wines. “Bordeaux” blends of Cabernet Sauvignon, Merlot, Cabernet Franc and/or Petit Verdot have become standard bearers. The learning curve has been long and is still steep.
The modern era of Virginia wines began in the 1980s. Many of the white wines were quite good, but red wines were marked by under-ripe characteristics and very high levels of methoxypyrazines. During the 1990s we learned how to mitigate greenness with aggressive canopy management and clever winemaking. After the turn of the century, progressive producers began focusing on site/variety relationships to take their wines to the next level. Virginia wine growers have found that white wine varieties are very adaptable to a diversity of soils. However, the Bordeaux varietals are very picky about where they grow and their preferences are reflected in wine quality.
Virginia receives an average three to four inches of monthly rainfall. Precipitation can’t be controlled, but soils can influence how much of that water is available to the vines. Virginia often experiences summertime precipitation during the critical period of berry and vegetative growth. This is problematic if the soil absorbs and holds this moisture, making it readily available to the vine. Without some level of hydric stress, vines will continue their shoot and lateral growth well past véraison. This abundance of vegetative growth delays maturity and contributes to green, vegetative characteristics in the wines.
This is why an understanding of the relationship of soils and slopes to specific varietal preferences can take our wines to the next level.
To dig deeper, a group of Virginia winegrowers representing three diverse vineyard sites met to discuss individual experiences with growing the four varieties. Included in the discussion were Luca Paschina, winemaker and general manager, Fernando Franco, viticuliturist, and Daniele Tessaro, associate winemaker at Barboursville Vineyards in Barboursville, Va.; Rutger de Vink, owner and Joshua Grainer, winemaker at RdV Vineyards in Delaplane, Va.; and Jonathan Weber, winemaker and Jim Law, winegrower of Linden Vineyards.
During our meeting, we tasted barrel samples that reflected micro-site influences on the wines. Given the diversity of the sites and the signature-blended wines, there was a satisfying consensus on many of the important aspects of soils and vines.
The group identified three aspects of a vineyard site that influenced the style quality and success of any planting: soil water holding capacity and permeability, slope (landscape form), and aspect (north, east, south or west).
Important vineyard site aspects
Water availability: Soil water holding capacity is critical in regulating the amount of water available to the vines. A certain amount of vine hydric stress is important for making ripe, concentrated red wines. In regions with abundant rainfall, soils with lower available water are considered most desirable. Deep soils with high clay content tend to have a larger capacity to hold water, while shallow, rocky soils with less clay are droughty.
In the early days of Virginia viticulture this relationship of water availability and wine quality was not on the radar. It was only after decades of trial, error and observation that we noticed that big, lush vines produced thin weak anemic red wines. Conversely, small spindly vines made the darkest, most concentrated lots.
Today the “hail Mary” approach to site selection is gradually being replaced by consulting soil scientists. Complex mosaics of quickly changing soil characteristics make soil mapping tricky at best, but at least it gives a reference point to start the journey.
Landscape form: While soil science is a complex endeavor, topography is pretty straightforward. A convex landscape form sheds water. The steeper the slope, the better the runoff, therefore less water is able to enter the soil. Much of the summertime rain in Virginia is in the form of thunderstorms that can drop copious amounts of water in a short period of time. Steep slopes shed this rain and much of it is unable to be absorbed by the soil. Certain clays can compound this run off, ironically making clay-based soils on steeper slopes more prone to excessive drought conditions.
Slope aspect: The sun angle of a south-facing slope will remove moisture faster from a vineyard site. The site will also be significantly warmer. This may or may not be advantageous depending on the site, variety and desired wine style.
Even though the sites where the three of us grow grapes are very different, there was a lot of consensus on variety preference.
Merlot: Out of all four varieties, Merlot requires a fairly steady access to water. Long dry spells in the summer can over stress Merlot and cause a photosynthetic shut down that can continue to disadvantage vine performance for the remainder of the growing season. Hot, dry conditions during ripening quickly spike sugar production and over-ripe characteristics in Merlot. The wine then loses its charm and freshness.
It’s no secret that Merlot prefers water-available clay, as has been demonstrated in Pomerol and St. Emillion. It also prefers cooler slopes.
Cabernet Sauvignon is very picky about where it grows. It grows too vigorously when it has access to water and nutrients. This is the problem. Virginia’s first attempts to grow Cabernet Sauvignon resulted in weedy, thin, green wines. Even in the warmest climates, Cabernet Sauvignon would only ripen well a couple of vintages a decade. In the past 15 years, however, there has been a renewed focus on soils that are appropriate to Cabernet Sauvignon and this has made a huge difference. If there is enough hydric stress during the summer, those grapes can ripen well even in the coolest parts of the state. Serious producers plant Cabernet Sauvignon on the warmest, least water retentive, and steepest slopes.
Cabernet Franc has similar, but not as exacting site preferences as Cabernet Sauvignon. The wine quality of Cabernet Sauvignon will fail miserably when planted in a high capacity soil. In that same soil, Cabernet Franc has a chance of making a fresh, herbal, easy drinking wine. The diversity of styles of a St. Emillion vs. a Loire is reflected in the chameleon-like qualities of Cabernet Franc grown in Virginia. On warm slopes with restrictive soils, these grapes can trend towards high alcohol, overripe characteristics. It needs cooler slopes with just a bit more water availability than Cabernet Sauvignon. Blocks with a diversity of soils can be problematic during harvest, as Cabernet Franc ripening times can be greatly influenced by soil differences.
Petit Verdot has become the latest darling in Virginia viticulture. Similar to Cabernet Franc, it is a “goldilocks” variety that likes the middle ground. On restrictive, warm sites it trends towards high alcohol, over ripe characteristics. However, it is late ripening, and consequently more clay-based, cooler slopes will challenge its ability to fully ripen. Grown on the middle ground, Petit Verdot is capable of producing a wine with some restraint, balance and nuance.
The piedmont and mountains of Virginia present even the smallest of vineyards with a plethora of soils and slopes. Rarely does one size fit all. We are learning that in order to take advantage of such a patchwork of micro-sites, small block plantings need to be tailored to soil and slope characteristics.
Then there is the weather. Cool wet vintages favor Merlot, while Cabernet Sauvignon shines with hot, dry summers. For these reasons, the flagship wines of top Virginia wine producers tend to be blends that can take advantage of the diversity of site and weather conditions.
This is an exciting stage of the evolution of Virginia wines. Many a vineyard block has been removed due to unsatisfactory wine quality. But once we get it right and the vines lose some of their youthful vigor, there is a dramatic improvement in wine quality. More sites are being chosen based on wine quality potential rather than easy tourist access. Presently the emphasis is more on soil mechanics (drainage, depth, water holding capacity, runoff) rather than the more subtle nuances of specific terroir expression. The latter will come as more producers start from a solid foundation and get a few more decades of vintages under their belts.
Over the past decade, Barboursville, RdV and Linden have developed an informal relationship of sharing experiences and expertise. When time allows, consultants and production teams trade visits. Time in the vines and tastings are emphasized.
Earlier this year the three producers met to discuss experiences with variety and site relationships. Some of the discussion from this meeting contributed to this article. Although each site and flagship blend is unique, we are finding a certain commonality in our observations.
Barboursville is located in central Virginia and the first vines were planted in 1976. Their Octagon is a Merlot-based blend with Cabernet Franc and Petit Verdot occasionally playing significant roles in some vintages. Small amounts of Cabernet Sauvignon are included in drier vintages. The 182 acre vineyard is planted on a density of 2.3 m by one meter on a clay based soil at an elevation of 600 to 800 feet.
RdV is located in the northern Virginia piedmont. Using grapes from vines planted in 2006, the Cabernet Sauvignon-based Lost Mountain is the flagship wine. RdV was the first Virginia vineyard site selected after extensive soil and site analysis. Only red wine is produced by the winery. The 17 acre vineyard is planted at a density of 2.1 m by 1.2 m on granite based soils at an elevation of 600 to 800 feet.
Linden Vineyards is a high elevation vineyard located on the Blue Ridge in Northern Virginia. The original vines were planted in 1985, but all the reds have now been replanted on different soils. Hardscrabble Red, Linden’s flagship wine, is primarily Cabernet Sauvignon with Merlot playing an important role. Cabernet Franc and Petit Verdot may be used in small amounts. The 20 acre vineyard is planted at a density of 2 meters by 0.8 to 1.2 m on both greenstone and granite at an elevation of 1,200 to 1,400 feet.
Wines & Vines, April 2018