As shoots continue to vaunt skyward we turn our thoughts to the subject of fruit set. Certain varieties for whatever reason are prone to poor fruit set. Merlot is a good example and because you can see poor berry set (coulure) and hens and chicks (millerandage). In 2004 we had significant fruit set problems in all our Merlot blocks. In fact, we harvested all the clusters with shot berries separately. We fermented 7 tons of this stuff and although we never thought it would make the final blend, it did. The resulting wine had a very low pH, 3.37, but was wonderfully fruity if simple. I digress. In 2005 our set was much improved. What happened? My initial suspicion is that the late rain of 2005 improved set, but in NorCal there is rarely a water deficit problem as early as bloom. 2004 was marked by an early budbreak, warm weather, but with subsequent cooler weather during bloom.
Mark Greenspan offers a few possibilities in this piece. Molybdenum deficiency is an interesting possibility, but since we have had bad then good set without adding any Mo, it is doubtful that is our issue. All this begs the question, is poor set bad? Well, I suppose that depends on your goals and how much it impacts your yield. If you believe lower yields improve you quality (which is debatable depending on what level you are reducing your yields to and from), then why worry about set? But certainly you want to be sure you have product to sell as well. Finally, having a significant proportion of clusters with shot berries will impact your wine and it may not be economical to harvest separately as we have done. All in all, it seems it would be best to have even fruit set, controlling your yields with other mechanisms.