Evaluation of Zinfandel Heritage Selections

The 2007 growing season was more moderate, without the heat wave of 2006. The result was far less sunburn in 2007. Harvest was compressed with two harvests only two days apart, Sept 11 and Sept 13. Yield varied from a low of 3.7 kg per vine to a high of 6.6 kg. Regarding yield components, berry wt was a very tight range, differing by only 0.2 g, from 1.5 g to 1.7 g per berry. The yield component clusters per vine, as in previous years, was very close among clones due to crop control via pruning. Cluster wt, also following previous the years? pattern differed widely from a low 174 g to almost 300 g. Given the similarity of berry wt, berries per cluster mirrored the difference patterns of cluster wt, with heavy clusters having the most berries and light clusters the least, a range of 108 to 183 berries. Berry samples for comparing selections were taken on a single date just prior to harvest. It shows a range of 24.1 to 26.6 Brix. Values of pH were very low, as is the usual case for Zinfandel at the Oakville Station, and in a relatively tight range, 3.10 to 3.18. Titratable acidity values were also relatively close, ranging from 7.32 to 8.07 (g/L). The patterns of difference in the 2007 data, are similar to those in the 2005 ? 2007 averages. Ripening was a little more uniform in 2007. Cluster numbers are greater in 2007 but this is due to an increase shoot number over year 2005, and a decrease in sunburn loss over year 2006.