The Sonoma Mountaintop where Volcanic Soils Create Marquee Wines | Wine Enthusiast
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The Sonoma Mountaintop where Volcanic Soils Create Marquee Wines

Stand at the top of Montecillo or Monte Rosso Vineyard as the wind whips, with the Pacific Ocean to the west and the distant skyscrapers of San Francisco to the south, and there’s no mistaking that you’re far, far above the valley floor.

That’s why it was imperative the region that houses these vineyards have an identity of its own. In 2013, Moon Mountain District became an American Viticultural Area (AVA) distinct from the Sonoma Valley. Several marquee vineyards, and the people who farm and work with them, have just begun to make its impact clear.

Between the town of Kenwood and city of Sonoma, Moon Mountain starts around 400 feet above sea level and rises as high as 2,200 feet. It’s 17,663 acres, with just 1,500 of those planted to wine grapes. Above the fog, those vines benefit from coastal winds with long, warm days and cool, dry nights during the growing season.

Volcanic soils bring it all together. Curled up against one of the Napa Valley’s most desirable AVAs, Mount Veeder, where volcanic soils also rule, Moon Mountain is a confounding treasure of fine grapes. It grows predominantly Cabernet Sauvignon and Zinfandel, coveted by winemakers on both sides of the Mayacamas Mountains.

Organic viticulturalist Phil Coturri farms more than 600 acres of vines in Sonoma County, nearly all of them on Moon Mountain. That includes Amapola Creek Vineyards & Winery, Kamen Wines, Lasseter’s Trinity Ridge, Stone Edge Farm and his own Winery Sixteen 600.

He says grapes from the region produce wines with “elegant bigness.” The tannins are supple and round, the acidity bright, the wines dark, inky and expressive of volcanic soils, able to achieve good phenolic ripeness at moderate alcohol levels. Ahead, the sites that define the AVA.

fog in vineyard
Hanzell Vineyards/Photo courtesy of Hanzell Vineyards

Hanzell Vineyards

A monopole on the southern edge of the appellation, at an average elevation of 800 feet, Hanzell was first planted to three acres of Chardonnay and three acres of Pinot Noir in 1953. Today, those plots are the oldest continuously producing vineyards in North America of each variety. The Hanzell clone of each are considered heritage clones, propagated elsewhere in California and Oregon.

The longest-serving winemaker for Hanzell, the late Bob Sessions, started his career across the mountain at Mayacamas Vineyards on Mount Veeder, where he worked alongside Robert Travers, a pioneer and the vineyard’s founder, until 1971. Sessions brought Hanzell to worldwide prominence with Pinot and Chardonnay, the two varieties for which it continues to be known, though they’re otherwise rare on Moon Mountain.

In 2016, Hanzell relaunched its Cabernet bottling, which it had produced from 1979–’92 before the vines were grafted to Pinot Noir. In 2012, it replanted two of those acres to Cabernet. The resulting 2016 vintage is intriguing, substantial in grace and structure.

A Moon Mountain vine in the fog
Photo courtesy of Hanzell Vineyards

“The common thread of the Mayacamas is the volcanic nature of the soils,” says Jason Jardine, Hanzell’s president and director of winemaking. “There’s a volcanic theme throughout the wines, a true legitimacy because of the geology. The Mayacamas are a fascinating bridge between Sonoma and Napa. Moon Mountain captures that bridge.”

Michael McNeill and Lynda Hanson make the wines, while the vineyard manager, José Ramos, has been on property since 1975.

The Hanzell estate, with its 46 acres planted to vines, is implementing integrated biological farming practices under Jardine. Outside inputs are limited, and natural nutrient cycles encouraged. The goal is to farm Hanzell the way it would have been prior to chemical applications: no tillage, no compost, not too much leaf pulling. Ideally, the estate would be 100% self-sustained. Vegetable gardens and fruit orchards on the property help feed workers.

In 2017, chickens, sheep, heritage pigs and two Maremma livestock guard dogs, Scout and Radley, joined the team to work the vineyards in their own way.

vineyard landscape
Monte Rosso Vineyard/Photo courtesy of Monte Rosso Vineyard

Monte Rosso Vineyard

Ranch manager Brenae Royal and her Labrador retriever, Violet Mae, are the modern-day overseers of the vast expanse that is Monte Rosso, 575 acres (250 acres planted) set from 690 to 1,300 feet above the valley floor. Royal has been in charge of the site, where she also resides, since 2015.

Remote and complex, it’s hard to imagine the foresight and fortitude it took for Emmanuel Goldstein to plant 75 acres to wine grapes here in 1886 or for Louis M. Martini to see the value in the red volcanic soils when he bought the vineyard in 1938.

Much of the original 1886 vines, including Zinfandel and Sémillon, still exist. The latter might be the oldest such planting in the world. Martini, who already had a Napa Valley winery established in St. Helena, planted Cabernet Sauvignon in 1940, some of which also continues to bear fruit.

Monte Rosso Ranch Manager Brenae Royal
Ranch Manager Brenae Royal and Violet Mae/Photo courtesy of Monte Rosso Vineyard

Both the Louis M. Martini Winery and Monte Rosso Vineyard were sold to E.& J. Gallo in 2002, which uses much of the vineyard’s Zinfandel and Cabernet Sauvignon predominantly for its Louis M. Martini and Orin Swift wines. Other producers who have sourced grapes from here include Robert Biale Vineyards, Carlisle Winery, Ravenswood, Rock Wall Wine Company, Bedrock Wine Co. and Amapola Creek.

While 23 varieties have been grown in this vineyard over its history, Royal and her crew farm 10 today. Almost half of the planted area, 118 acres, is devoted to Cabernet Sauvignon. The challenging site is divided into 64 blocks and 105 sub-blocks because of its multitude of variations. Royal figures 60% of the site is sloped, with the remainder planted along a homogenous, relatively flat bench where volcanic debris settled, the red hill loam soil both porous and fertile.

“It’s the soil that brings Moon Mountain together, and the elevation,” she says. “The acidity, tannin and earthiness are its most pronounced signature. There’s ingrained complexity from Monte Rosso.”

Montecillo Vineyard
Montecillo Vineyard/Photo courtesy of DuMol

Montecillo Vineyard

Kaarin and Mike Lee bought Montecillo in 2001 from a couple of gentlemen who had sold the grapes to Kenwood Vineyards. Mike, who died in 2011, was one of the founders of Kenwood and its winemaker for many years.

An old-vine, dry-farmed block of St. George rootstock Cabernet Sauvignon planted in 1968 had made up the backbone of the winery’s famed Artist Series Cabernet every year. When the Lees took over, they replanted the rest of the vineyard, block by block.

“I will never forget the day Mike came home and told me that Montecillo was for sale,” says Kaarin. “We were in the market for a vineyard after leaving Kenwood Vineyards. We wanted to stay in the wine business as growers. We thought we died and went to heaven because we were able to purchase what we always referred to as ‘the crown jewel.’ ”

wine grape harvest
Harvest at Montecillo Vineyard/Photo courtesy of DuMol

Facing west at up to 1,800 feet above sea level, Montecillo has cool mornings and hot afternoons, perfect growing conditions. The eroded soils are rocky and steeped in iron-rich red clay loam with a volcanic quality. The vines are at least 15 years old.

Chuy Ordaz farms the vineyard for Kaarin and her daughters, Britt Felix Lopez and Katherine Lee. The old vines have been organically farmed for four years, and the rest of the vineyard completed that transition last year. Much attention is paid to canopy management during the growing season.

Napa Valley-based winemaker Massimo Di Costanzo was able to buy three tons of Cabernet Sauvignon beginning in 2017.

“The wines are super distinct, they tell a story,” DiCostanzo says. “The volcanic soils, dry-farmed, planted in the 1960s, you don’t see a lot of Cab like that. There’s so much natural character.”

Turley, Bedrock, Beekeeper Cellars, DuMol and Ordaz Family Wines are other producers that buy grapes from Montecillo.

Aerial shot of Nun's Canyon Vineyard
Nun’s Canyon Vineyard/Photo courtesy of Hamel Family Wines

Nun’s Canyon Vineyard

The Hamel Family ranch is on the valley floor along Highway 12 in Glen Ellen. Six miles away, up a steep, bumpy road on the northernmost edge of the appellation, Nun’s Canyon Vineyard sits between 1,300 and 1,700 feet in elevation. The Hamels bought it from St. Francis Winery in 2013.

The site is steep and brimming in red clay loam soils, its underbelly a mixture of fractured basalt and gravel. The Hamels made their first Cabernet Sauvignon from here in 2013. They began to use biodynamic techniques and dry-farm the site in 2018.

Most of its 125 acres are planted to Cabernet Sauvignon, but other grapes cultivated include Cabernet Franc, Merlot and newer plantings of Grenache, Syrah and Mourvèdre.

harvesting grapes in vineyard
Pedro Parra in Nun’s Canyon Vineyard/Photo courtesy of Hamel Family Wines

John Hamel oversees winegrowing and winemaking here. With Chilean-born soil specialist Pedro Parra, who holds a Ph.D. in terroir from the Paris Center of Agriculture, Hamel is analyzing Nun’s Canyon’s microterroirs. They’ve identified eight variations, from shallow silty basalt to stony basalt. Their results are used to influence replanting decisions and blending in the cellar.

“The soils are all volcanic, but volatile,” says Hamel. “They can change on a dime. You can’t see the differences from the top and that makes it super difficult to farm. You can have six different soil types in one block.”

This gives him versatility, but logistical challenges. He conducts 50 different picks of the vineyard during harvest and vinifies those by soil type. The fractured basalt is broken, weathered and quite porous. In another corner of the vineyard are the oldest vines, planted in 1994. They sit in silty, sandy soils. Hamel finds their fruit much more intense and possessed of depth.

“The wines are stony and mineral, they have an elegance and are more complex than just concentrated in fruit,” he says. “You get delicate, fine wines.”