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Planting a Field-Blend; part 1

September 19, 2010

We are in the midst of planting a new vineyard block on a hot exposed site that has well drained shallow soils that lie on top of an impermeable layer of volcanic ash. The vines will not have much access to water and to make matters more interesting we are going to dry-farm the grapes. We are planting this small block to a field-blend of 8 different late-ripening grape varieties, primarily Grenache, using cuttings from our ancient field-blend.

In 1982 when Otto Teller purchased Old Hill Ranch, there were 12 acres of ancient vines out of 30 plantable acres. Today it is closer to 25 acres of vineyard. The first addition came soon after the purchase when our neighbor asked if he could lease 8 acres to plant a vineyard of Cabernet Sauvignon. Otto agreed to a 20 year lease that expired in 2004 and now we farm and make wine from this block.

In terms of geography and geology this 8 acre hillside Cab vineyard is very different from the ancient vineyard located 50 feet across the dry creek-bed on the relatively flat valley floor. The Cab block is on a hill that rises above the Sonoma Valley floor 60 feet. The vines on this block are more exposed facing the hot afternoon sun and the average temperatures are considerably warmer.

There are two separate aquifers under the two adjacent blocks. The ancient vine are on the Sonoma Creek aquifer which is relatively shallow at around 40 feet deep and the water tends to be high in iron and not particularly delicious to drink. The aquifer under the cab is slightly deeper at 60 feet and it is very generous in terms of the quality, quantity and it is ever so slightly warmed by geothermal activity.

The soil types and the soil depths of the two blocks are different. The ancient vines are on deep redish (iron rich) clay-loam soil while the cab block is on shallow brown magnesium rich clay. The deep soil in the ancient vines is important because it allows the vines send their roots way down to search for water which is there only source of moisture. However the depth of the soil on the cab block is shallow averaging around three feet and then it turns to Volcanic Tuff.

Sonoma Valley has a rich and relatively recent volcanic history. The Tuff is a slightly porous conglomerate of volcanic ash mixed with rocks from an eruption approximately two million years ago. Dry-farming grapes on this Tuff is going to be challenging….for both the grapes and the farmer.

The Cabernet vines that are planted on this block have made some fantastic wine over the years but they are children of the 1980’s and thus they are planted on AXR1 rootstock. AXR1 was the favorite rootstock until it was discovered to be susceptible to phylloxera, a root aphid that severely limits the vines longevity. While most vines show symptoms of the disease they are surviving and producing and it seems generous helpings of compost keep the phylloxera in check. However in 2007 we pulled out two acres of vines that were planted on the top of the hill in the shallowest soils. We subsequently ripped the soil and let if fallow for two years and then this spring we planted it to St. George rootstock.

The obvious question is why take the most difficult vineyard site and plant it to an old out of date vineyard paradigm without the use of irrigation?

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