Field blends and co-fermentation

Field blends predate the modern habit of planting single varieties in blocks, and they were the norm in much of Europe before phylloxera forced wholesale replanting.

Surviving old field blends are prized precisely because they cannot be recreated: the mix reflects choices made a century ago by someone whose reasoning is unrecorded.

In a true field blend the varieties ripen at different rates and are picked at one time regardless, so some fruit is riper than others. That heterogeneity is part of the character rather than a defect to be corrected.

Co-fermentation of separately picked varieties allows the pick date for each to be optimised while still fermenting them together. Northern Rhône Syrah with a small proportion of Viognier is the best-known case, where co-fermentation is associated with more stable colour.

Blending after fermentation offers by far the most control, because each component can be assessed and the proportions chosen. It is what Bordeaux and Champagne do.

Notable surviving field blends include the Gemischter Satz of Vienna, which has protected status requiring at least three white varieties interplanted, and old Douro vineyards where the exact composition is frequently unknown.