The Harvest Decision — Is it all about Brix?

Now that we are nearing the end of September, it’s time to start tracking the ripeness of the fruit to decide when to harvest. Earlier in the week I visited Black Ridge Vineyards on Black Road in Los Gatos where I will be buying Syrah and Cabernet Sauvignon.  I also evaluated my backyard vineyard (Monte Roble Vineyard).
I was interested to measure the brix, or percent sugar, of the fruit and also taste it to evaluate it’s ripeness and how close we are to harvest.  This growing season has been cooler than normal, which is keeping sugar levels low and potentially pushing harvest back into November. 
Black Ridge sits at an elevation of about 1,100 feet and faces east overlooking Lexington Reservoir.  I love the views from this vineyard. Downtown San Jose is in full view to the north and Mount Umunhum to the east.
I brought Tria along to help me sniff out the best grapes and maybe find a bird or two along the way. I think she’s already on to something.
The first several rows of the upper vineyard were grafted over to Grenache scions in the spring. The first year’s growth looks good and healthy.  
These new vines will benefit from established rootstock and should produce a small crop next year.  Grenache grows well at Black Ridge and is becoming more popular as a single varietal and also in Rhone style blends with Syrah and Mourvedre (GSM).
The vineyard rows at Black Ridge are divided between several different clones of each varietal.  I selected rows in the middle of each block for the variety and clones I plan to purchase and collected berry samples into Ziploc bags.
I walked the entire row length and collected berries from each side at a set interval to get a representative sample.   Grapes on the westward facing side of the row get the hotter afternoon sun and typically ripen more quickly.  Differences in soil type and water holding capacity also affect vine growth and ripening.
And now on to Monte Roble Vineyard in my backyard vineyard to collect similar berry samples. This vineyard is at an elevation of about 450 feet and sees a bit higher summer temperatures than Black Ridge. 
The vineyard is completely enclosed in bird netting. Since my vineyard is small and the only game in town, the birds would certainly win if I did not net the vines.
I crawled under the netting to enter the big tent and collected berry samples from both the lower Syrah block and upper Cabernet Sauvignon block. It’s a steep hillside and not easy to navigate the hanging fruit, trellis wires, irrigation lines and spider webs.  This vineyard is planted on a much tighter grid than commercial vineyards since tractor access is not needed or even possible.
The netting has done a fine job of keeping the birds out, but here you can see Raccoon damage.  The Raccoons patiently eat whole bunches right through the netting.   I guess it beats raiding garbage cans and scavenging for old dog bones.
Here is where we get to the more technical part which may take on the tone of a technical report from my days as an environmental consultant and hydrogeologist. 
The berry samples in the photo above are arranged with Syrah across the top and Cabernet Sauvignon across the bottom.  The Black Ridge berries are the first two samples in each row while my backyard vineyard berries are on the far right.  In general, you can see that Syrah berries are larger than Cabernet Sauvignon and my backyard berries are smaller than Black Ridge.
Who cares?  Well, small berry size is often associated with more intense flavors and a higher ratio of skins to juice content.  Skins are responsible for color intensity and soft tannins, which provide structure to the wine.
I crushed the berries in the bag to get juice samples. Before measuring the brix, I tasted each sample to evaluate if there were any green or herbaceous flavors and the balance between sweetness and acidity.  I also looked at the color of the seeds and chewed on them. Brown, crunchy seeds indicate that the grapes are mature and will produce a wine with complex flavors, but without undesirable green flavors, such as bell pepper.
I placed a few drops of juice on the refractometer glass and sandwiched it between the glass and cover.
A direct reading of brix, or percent sugar, was then made through the refractometer. Last year we harvested at about 24 brix, which when converted by alcoholic fermentation, produced a finished wine with about 13.5% alcohol. For wines meant to mature and develop complexity with ageing, I like alcohol in the 13 to 14 percent range.

Here are the results. The Black Ridge grapes average out to about 20 brix.  At this time last year the brix was almost 22. Monte Roble Vineyard is a bit further along, but considering that we harvested on October 1st last year, it is also behind.  I’m guessing that on the brix front, we are 2 weeks behind last year and will be even further behind if the weather stays cool, as forecasted, over the next 10 days.  If the harvest decision is based on brix alone, Black Ridge may be looking at an early to mid November harvest, and at that point, the threat of rain damage is very real.
On a positive note, the seeds from both vineyards were nice and toasty brown. Monte Roble Vineyard seeds were a bit darker and more crunchy than the Black Ridge, but not all that much different.
In the final analysis, I am reminded of what I have learned over-and-over again in my UC-Davis viticulture and winemaking classes, and that is to not overly focus on brix measurements when making the harvest decision.  If I consider taste, acidity, and seed color/crunch, we are almost there.  If the weather cooperates and we can eek out just enough sugar to make a 12.5+ percent alcohol wine, we will be in good shape.  Hopefully that’s before Thanksgiving!