5 Facts About Grape And Raisin Production In California

The California vineyard most people picture sits on a rolling hillside near the coast with a tasting room at the end of the drive. The state’s grape industry is much larger than that picture. A good part of it lies in the flat, hot San Joaquin Valley, where grapes are grown to be dried into raisins or packed for the fruit bowl, and where four years of drought have made water the question behind every planting decision.

1. Wine grapes lead, but raisins and table grapes fill the valley

According to the USDA National Agricultural Statistics Service grape acreage report for the 2014 crop, California had 928,000 acres of grapes. Wine types covered 615,000 acres, raisin types 192,000 and table types 121,000. Chardonnay and Cabernet Sauvignon led the wine varieties, Flame Seedless led the table grapes, and Thompson Seedless remained the main raisin variety, used for raisins, fresh fruit, concentrate and wine alike.

2. Raisin acreage is shrinking and aging

Raisin-type acreage fell 5.4 percent between 2013 and 2014, from 203,000 acres to 192,000, while wine and table acreage each rose slightly. The raisin vineyards are also old. Fresno County alone held close to 119,000 acres of Thompson Seedless in 2014, and all but about 800 of those acres had been planted in 2006 or earlier. Only about 2,000 acres of raisin vines statewide were too young to bear, against 50,000 acres of young wine grapes, so few growers are putting in new raisin vineyards.

3. A pound of raisins starts as more than four pounds of grapes

California raisins are dried in the sun where they grew. In the traditional method, crews cut the bunches in late summer and lay them on paper trays on the ground between the vine rows, and the fruit dries there for two to three weeks before it is gathered. The raisin industry’s own figures put the ratio at roughly 4 to 4.5 pounds of fresh grapes for each pound of raisins. That loss of weight is why a heavy raisin crop on the vine turns into a modest tonnage in the box, and why a rain while the fruit is still on the trays is the raisin grower’s worst news of the year.

4. Table grapes are sold by the box

Table grapes are packed in the field into boxes holding 19 pounds of fruit, and yields are quoted in boxes per acre. University of California cost studies have assumed yields from roughly 850 to 1,750 boxes an acre, depending on variety and vineyard. The newer varieties tend to yield more, but a table grape vineyard is expensive to establish: tall trellises, canopy work and careful hand harvesting all add cost before the first box is sold.

5. Vines use far less water than nut orchards

Water is the reason grapes and tree nuts are compared so often. University of California research puts the seasonal water use of a mature raisin vineyard in the San Joaquin Valley at roughly 19 to 26 inches, depending on canopy size, while field studies of mature almond orchards in the valley have measured around 48 to 54 inches. The figures measure evapotranspiration, the water a crop uses through its leaves and loses from the soil, and the irrigation applied has to cover that plus losses.

Raisin vineyards were traditionally furrow irrigated, with water run down shallow channels between the rows. Many vineyards of every type now use drip lines instead, usually one per row, often hung from the lowest trellis wire, with emitters spaced along the line. Drip lets a grower match the water applied each day to what the vines are using in that day’s heat, and puts it where the roots are instead of across the whole floor of the vineyard. Growers can also hold water back on purpose at certain stages, a practice called deficit irrigation, which in wine grapes is used to keep vines from growing too much leaf. In a dry year, when surface water allocations are cut and wells are pumped harder, that precision decides how far a limited supply will stretch.