Lodi's San Joaquin Series Soil - Exploring the Jahant, Cosumnes River, and Alta Mesa Viticultural Areas

Reddish sandy/clay loam soil and blue oak characteristic of Lodi's Jahant AVA along Liberty Rd.

As we conclude our California Wine Month journey through Lodi's wine history, we explore the three remaining sub-appellations that complete the region's diverse tapestry: Jahant, Cosumnes River, and Alta Mesa AVAs.

Located between the Sacramento-San Joaquin River Delta to the west and the eastern hillside appellations, these three regions share a unique common denominator: variations of California's official state soil, the San Joaquin series. Characterized by shallow sandy clay loam over hardpan layers, these soils initially seemed less ideal for viticulture than Lodi's deep sandy plains. However, innovative farming families in the 1980s discovered that deep ripping techniques could transform these terraced floodplains into exceptional wine-growing terrain.

From the cool, fog-influenced vineyards of Jahant and Cosumnes River to the "high table" mesa topography of Alta Mesa, these appellations showcase how Lodi growers turned agricultural challenges into opportunities, establishing diverse plantings that range from classic Cabernet Sauvignon to Portuguese Port varieties. In this final exploration, originally authored by wine journalist Randy Caparoso, discover how these three AVAs complete the story of Lodi's seven nested appellations.

San Joaquin Series Soil

The distinguishing common denominator shared by the Jahant, Cosumnes River and Alta Mesa AVAs — sandwiched between the Sacramento-San Joaquin River Delta to the west and the lower foothill appellations of Clements Hills, Borden Ranch and Sloughhouse to the east — is their variations of the official California state soil (since 1997) classified in the San Joaquin series. San Joaquin soils are characteristic of the lower elevation (generally below 100-ft.), terraced, shallow-topsoil, floodplain topography predominant in much of Northern San Joaquin Valley and Sacramento Valley.

Winegrower Ron Silva in his Silvaspoons Vineyards, dominated by the shallow, yellowish brown sandy/clay loam found throughout Lodi's Alta Mesa AVA

A summary of the benefits and features of soils falling within the range of the San Joaquin series:

• The surface layer is commonly a reddish to yellowish brown, partial sand/clay loam 2 to 6-(at the most)-feet in depth, formed above a cemented clay or sandstone hardpan that restricts root and water penetration.
• While very useful for irrigated crops such as wheat, rice, fruit and nut orchards and ranching, historically these areas were not as favored for deeper rooted grape crops as the Mokelumne River area surrounding the City of Lodi with its far deeper (as much as 90-feet), more porous and vigorous alluvial sandy loam, falling in the Tokay series.

In this graphic, "soils with hardpans" align with boundaries of Lodi's Jahant, Cosumnes River and Alta Mesa AVAs, while the Mokelumne River AVA is defined as a "deep soil" appellation

• The transition between the deep sandy loams of the Mokelumne River AVA and the shallower loams of the Jahant AVA has always been traced by Peltier Rd. running east-west, north of the City of Lodi, and north of the winding Mokelumne River where it crosses W. Peltier Rd. between N. Davis and N. Lower Sacramento Roads.
• Starting in the 1980s, longtime Lodi farming families such as the Langes and Schatzes, and newer arrivals like Netherlands-born Pieter den Hartog, began to make use of deep ripping equipment to break up hardpan and plant wine grapes extensively. This enabled them to establish deeper loam surfaces of increased vigor, mixed with finer textured subsoils just above and below the hardpans to increase a clay content that is particularly ideal for the formation of phenolic content important to the quality of high-demand varieties such as Cabernet Sauvignon and Merlot.
• In the Storie Index cited in the 2005 petition submitted to the TTB to establish Lodi's seven nested AVAs, the soil vigor of the Jahant, Cosumnes River and Alta Mesa areas were rated in the 24-40 range — less vigorous than the soil in Mokelumne River (rated 80-95), but more vigorous than the hillside areas of Clements Hills, Borden Ranch and Sloughhouse (rated 15-30).

Jahant AVA

• Geographically the smallest of Lodi’s seven AVAs — comprising 28,000 acres, with 9,000 planted acres — extending west-east in the center of the Lodi AVA, bordered by Dry Creek and Peltier Road to the north and south, and located mostly in San Joaquin County.
• Name derived from Peter Jahant who, with several brothers, first settled in the area in the vicinity of Acampo during the 1850s; thereafter, lending the family name to numerous local landmarks (Jahant Slough, Jahant Rd., Jahant Equestrian Center, and several Jahant Vineyards). 
• This AVA is marked by erosion in relatively flat topography with fairly consistent 10’ to 80’ elevations. 
• Sits on highly desiccated river terraces and old floodplain deposits; consisting primarily of shallow, pinkish sandy clay loam in the San Joaquin series on an indurated duripan; generally sandier at the surface with older, cemented, root restrictive layers at the sub-surface, with a few sections of deeper sandy loam. 

Reddish sandy/clay loam of Lodi's Jahant AVA in LangeTwins Family Vineyards' Jahant Woods 01 Vineyard

• Climate is similar to Mokelumne River AVA to the immediate south, but receives more cold air drainage and entrapment with vineyard pockets that are even cooler than most parts of Mokelumne River. 
• Has lower precipitation than east side AVAs (Sloughhouse, Borden Ranch and Clements Hills); but more Delta fog influence, hence the coolest growing seasons on average (along with the Mokelumne River AVA) of the seven Lodi AVAs. 

Nero d'Avola in LangeTwins Family Vineyards' home estate in Jahant-Lodi

• White varieties (Chardonnay, Viognier, Sauvignon Blanc) have been extensively planted over the past 25 years, although black skinned skinned grapes (Cabernet Sauvignon, Merlot, Petit Verdot, Primitivo/Zinfandel, Carignan, Petite Sirah, Barbera, Sangiovese, Tempranillo, Teroldego, Montepulciano, Nero d’Avola) are also performing well. 
• Excellent examples of Jahant grown wines include LangeTwins Family Vineyards Sangiovese Rosé, LangeTwins Family Vineyards “Musqué Clone” Sauvignon Blanc, LangeTwins Family Vineyards Montepulciano, LangeTwins Family Vineyards Teroldego, Bokisch Vineyards Liberty Oaks Vineyard Tempranillo, Oak Farm Vineyards Hohenreider Vineyard Zinfandel, and St. Amant Winery Barbera.

Cosumnes River AVA

• Located mostly in Sacramento County; consisting of 54,700 acres, with the smallest amount of planted wine grapes (about 3,500 acres) of Lodi’s seven sub-AVAs; bordered on the west and east sides by Interstate 5 and California Hwy. 99.
• Named for the Cosumnes River which flows down from the Sierra Nevada to join with the Mokelumne River to mark the southwest corner of the AVA, between Walnut Grove and Thornton; and also, in the vicinity, the 1,450-acre Cosumnes River Preserve. 
• The AVA’s immediate proximity to Delta fog and near-sea level elevations (5' to 48') make this one of Lodi’s cooler climate appellationss (along with Mokelumne River and Jahant to the south). 

Vermentino growing in Cosumnes River-Lodi's clay loam (with clumping clay surface soil during dry days of summer, turning sticky during wet winters) in Peltier Winery's R&G Schatz Farms

• Dominated by younger, organic, moderately fertile, silty, alluvial soils in lower areas consisting of floodplains, sloughs and wetlands; while intermediate age, reddish gravelly clay loam soils in the San Joaquin series (also classified as Abruptic Durixeralfs) with more water-holding capacity, but also a tendency to harden and compact at the surface during the dry summers, are found in the remaining 40% of the AVA.
• The cooler Delta influences of this west side AVA have proven exceptionally friendly to white wine varieties (particularly Chardonnay, Sauvignon blanc, Pinot grigio, Vermentino) as well as reds (Cabernet Sauvignon, Merlot, Syrah).
• Excellent examples of Cosumnes River grown wines include Peltier Winery “Black Diamond” Vermentino and Peltier Winery “Black Diamond” Sauvignon Blanc.

Alta Mesa AVA

• AVA consisting of 55,400 acres with about 5,300 acres of planted grapes.
• Located just east of the Cosumnes River AVA, north of Dry Creek, and falling completely within Sacramento County.
• Name comes from the Spanish phrase (alta mesa, or “high table”) that the petition explained was commonly used by local ranchers, farmers and vintners for the area to describe the region’s tabletop or mesa-like topography (ranging from 35’ on the western edge to 135’ in the east) and hence, numerous local landmarks such as Alta Mesa Rd., Alta Mesa Farm Bureau Hall (listed on the National Register of Historic Places), Alta Mesa Community Hall, Alta Mesa Fair, Alta Mesa Dairy, and Alta Mesa Gun Club. 

Dropped Tannat grapes on the San Joaquin series soil in Alta Mesa-Lodi's Silvaspoons Vineyards

• Fairly flat topography of intermediate elevation river terraces and alluvial fan deposits built up by the American and Cosumnes Rivers; consisting primarily of dense, reddish, gravelly clay loam soils primarily in the San Joaquin series, with fairly shallow (2’ to 5’), loose topsoil on fairly thick hardpan layers, requiring extensive deep ripping before planting. 
• Prairie environment; climate influenced by Delta breeze, with less wind and marginally higher temperatures than the lower lying AVA (Cosumnes River) to the immediate west.

Touriga Nacional in Alta Mesa-Lodi's Silvaspoons Vineyards

• Initial plantings relied heavily on standard red wine varieties (Cabernet Sauvignon, Merlot, Malbec, Syrah, Cabernet Franc, Primitivo/Zinfandel); then diversified to include a good number of alternative varieties (Verdelho, Vermentino, Albariño/Alvarinho, Grenache blanc, Moscato Giallo, Torrontés, Tannat, and black skinned Port grapes such as Touriga Nacional, Touriga Francesa, Tinta Roriz/Tempranillo, Tinta Cão, Souzão, Alvarelhão and Tinta Amarela). 
• Excellent examples of Alta Mesa grown wines include Fields Family Wines Delu Vineyard Vermentino, Fenestra Winery Silvaspoons Vineyards Verdelho, Wise Villa Winery Torrontés, Uvaggio Primitivo, Jeff Runquist Silvaspoons Vineyards Touriga, Jeff Runquist Silvaspoons Vineyards Tannat, and PRIE Vineyards Silvaspoons Vineyards Mencía.

Alta Mesa-Lodi grown Verdelho harvest in Silvaspoons Vineyards

Completing Lodi's AVA Story

The Jahant, Cosumnes River, and Alta Mesa AVAs demonstrate a defining characteristic of Lodi's wine industry: the ability to innovate and adapt. What once seemed like agricultural limitations became opportunities through ingenuity and determination.

Together with the Mokelumne River, Clements Hills, Borden Ranch, and Sloughhouse AVAs, these seven nested sub-appellations tell the complete story of Lodi's remarkable diversity. From sea level to 590 feet elevation, from 90-foot-deep sandy loam to shallow clay over hardpan, from century-old own-rooted vines to cutting-edge plantings of rare varietals, Lodi's terroir offers something truly unique in California wine country.

The Evolution of California's Most Dynamic Wine Region

From a single 39,000-acre appellation in 1986 to a sophisticated system of seven nested AVAs totaling over 100,000 acres, Lodi's journey reflects the evolution of American viticulture itself.

Today, Lodi stands as California's largest wine grape growing region and one of its most innovative, producing nearly 100 different grape varieties across seven distinct appellations. From the Miwok people who first named the Mokelumne River to the multi-generational farming families who continue to steward this land, Lodi's wine history is a testament to the power of place, the value of persistence, and the rewards of respecting terroir.

As you enjoy wines from Lodi, remember that each bottle carries within it the story of ancient soils, cool Delta breezes, innovative growers, and a community committed to sustainable viticulture and authentic expression of place. This is Lodi: California's most dynamic wine region, with a past as rich as its future is bright.

Thank you for joining us on this California Wine Month journey through Lodi's remarkable wine history.