"Working the Land" (Viticulture)

Viticulture: Merlot At-A-Glance
Vigor (low/high)
Relatively easy to grow Mildly vigorous; need to control leaf growth through rootstock, soil, and clone-matching, as well as (where legal) irrigation
High quality in a wide variety of terroirs. Unlike Cabernet Sauvignon, Merlot performs well in soils with high clay content; best to avoid vigorous fertile soils Can withstand cold to an extent
Yield (potential)
Moderate to high, depending on vigor and winemaker intent; must be managed
Growth cycle
Early budding (prone to late-winter and spring frost) – Mid-season ripening
Prone to coulure and rot (in wet years) and downy mildew, but otherwise resistant to oidium and pests/insects

Growing and Making Merlot (In California)

Frankly, Merlot is quite similar in flavor and texture to Cabernet Sauvignon and is often and is easily confused with it in blind tastings. Yes, videos abound on the internet showing people making this very celebrated “Oops!” The reality is that “classic merlot” is hard to pin down. Folklore has it that it’s identifiable by its relative roundness, plumpness, and lack of tannin compared to Cabernet Sauvignon. And that can be true, but that stereotyping is largely misleading. For example, when merlot is planted in rocky, well-drained soils in top appellations, it can be every bit as structured, tannic, and ample as Cabernet Sauvignon. The problem is that too often wine drinkers buy easy-drinking, inexpensive Merlot and it delivers the opposite. And one of the world’s most expensive wines – Petrus -- is always over 90% Merlot and yet is built like a great Cabernet and ages for decades. The take-away is be aware and be open-minded as you explore the world of Merlot! Spoiler Alert -- Merlot is one of California’s greatest wine hacks for the Cabernet Sauvignon lover on a budget. Many winemakers will put the exact same care into their Merlot as they do with their Cabernet Sauvignon but will sell it for a fraction of the price. In 2017, Napa County’s average price for Cabernet grapes translated to roughly a $75 bottle Signature Styles & Chaof wine, whereas Merlot’s average came out to a $34 bottle.

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 where 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 wine research facility, did a study on the topic. Though the study is based on Chardonnay grapes, they concluded that the following holds true for all winegrapes: “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 Merlot, according to the classic view, expresses itself in the glass based on the type of soil in which it is grown.

Alluvium/Alluvial Fans. Each alluvial fan has its source from a single channel of run-off from the mountains and consists of various sizes of sediment. These soils are well-drained, and vines grown on them typically have very deep root systems. Depending on the size of the sediment, an alluvial fan will have a different degree of slope. Larger debris is sloped more steeply, but rarely more than 10 degrees. Vines grown on benchland soils are usually healthy and produce high-quality grapes. 

  • California locations: Napa Valley (Rutherford Bench, Oakville, etc.), Sonoma County (Dry Creek, Alexander Valley), Lodi (Mokelumne River), Paso Robles (San Miguel), Santa Barbara (Happy Canyon)

Loams: Loam is nearly an equal mix of silt, clay, and sand, as well as an organic matter called humus, formed by the decomposition of leaves and other plant material by soil microorganisms. Loam is very fertile and typically causes vineyards to be over-vigorous. Because of the vigor, most loam soils produce wines that have little flavor and color. Despite this, loam soils offer great potential with wines made from vineyards that have rigorous pruning regimes.

  • California locations: There are no specific regions to call out.

Mountain/colluvial soils = Mountain fruit is often compact and concentrated, its berries tiny from seasons of struggle and loaded with flavor due to lower yields. The accompanying thermal amplitude elongates the growing and ripening seasons.

  • California locations: Sonoma’s Moon Mountain, Sonoma Mountain, Fountaingrove; Napa Valley’s Mt. Veeder, Diamond Mountain, Howell Mountain, Spring Mountain and Atlas Peak, the Santa Cruz Mountains

Limestone soils: Limestone is made of calcium carbonates, has a high pH and is usually grey in color. Sometimes a region’s hydrology will leach the carbonates out of limestone. What's left is an iron-rich clay devoid of calcium. The iron oxidizes, turning the clay into the rusty reddish color responsible for its name: “Terra Rossa” (Red Earth). In limestone soils, Merlot is more perfumed and elegant

  • California locations: Gabilan Mountain Range in Central California, San Benito County, Paso Robles

Clays: The best Merlot sites are clay-based. Because it holds on to moisture, clay stays cooler longer into the growing season than larger-grained soil. So, it takes longer for the grape clusters above it to ripen. However, clay tends to be very fertile because it stores both water and nutrients to an extreme.  Balancing out the pyrazines is key, especially with a grape such as Merlot which has a proclivity to green (pyrozininc) flavors. Clay is also capable of fuller bodied and more structured Merlot. 

  • California locations: Clay soils can be found in many locations 

As with many other varieties, Merlot can be a delicious wine either as a stand-alone (e.g. mono-varietal/100%) or in combination with related grapes in the Bordeaux family, notably Cabernet Sauvignon, Cabernet Franc, Malbec and Petit Verdot. While these wines may still say Merlot on the label (if they are minimally 75% Merlot -- 85% for export), some may carry proprietary names. As an example, Joseph Phelps Insignia in 1975 was predominantly Merlot. As with all other varieties, diversity can also be magnified by the choice of clones/selections of grapes.

Officially, there are some 37 clones officially authorized at UC Davis. For the longest time, the lion’s share of Merlot planted were Clones 1, 3 (a variant on 1) and 6. The first two can be traced to Inglenook back in the 1880s, while the latter was sourced from Louis Martini at his Monte Rosso vineyard in the 1950s. Interestingly, but making a lot of sense given its pre-phylloxera clonal diversity, a number of Cabernet clones in California made their way here via South America, specifically from Argentina (Clone 8). Moreover, clones also came from Italy (clones 10, 11, 12, 13, and 21) and, as one would expect, many from Bordeaux. Merlot’s heirloom clones come from celebrated spots -- clone 18 (Sterling’s Bear Flats), clone 27 (Niebaum Coppola via Larry Hyde) and Clone 35.1 (Three Palms Vineyard, also from Larry Hyde). 

For more information on clones created in California, visit UC Davis’s Foundation Plant Services on the Merlot Grape Variety.

As managing vigor is an important issue with Merlot, to mitigate herbaceous character and balance fruit/vegetation, matching soil to rootstock selection is critical. Merlot’s medium-high vigor can quickly create a dense canopy due to lateral shoot development. High-vigor rootstocks such as Ramsey and O39-16 should be avoided. It is adapted to cool to warm climate regions. Merlot does well in deep, sandy loam or well-drained soils with good moisture-holding capacity (e.g. clays).  Finally, compared to Cabernet Sauvignon, Merlot has less of a blue-black hue, a higher sugar content and lower malic acid, a thinner skin, and fewer tannins. It normally ripens up to two weeks earlier than Cabernet Sauvignon. 

While planted across the state, most premium Cabernet Sauvignon is planted in the North Coast and mid-Central Coast areas and as a rule is trellised in VSP (vertical shoot position) with spur (cordon) and cane pruning to balance sun exposure, minimize rot and allow for canopy management (leaf plucking, etc.). For higher vigor sites, Smart-Dyson, lyre, and GDC systems are better suited. Coupled with spacing and appropriate vine density planting (high versus low number of plants per acre), these choices can make the difference between high quality or not.  

 For a deep dive into Merlot viticulture, visit the Merlot chapters of Wine Grape Varieties in California by UC Davis’ Division of Agriculture and Natural Resources.

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Sustainability and California

As an agricultural industry, the California wine community has a long history of adapting to change and demonstrating its commitment to sound environmental practices and social responsibility. Building on these efforts are the educational and certification programs of the California Sustainable Winegrowing Alliance (CSWA) covering practices from the ground to the glass. Established by Wine Institute and the California Association of Winegrape Growers, CSWA is the most comprehensive and widely adopted wine sustainability program in the world, and– together with other important sustainability programs in regions throughout the state– has also made California wine a leader in addressing climate change.