when to harvest the grapes is a tricky thing to decide - let's delve at PumpjackPiddlewick

As we head into August, it’s time to start testing the grapes in earnest to determine and decide when grapes might be ready to be picked. But how do you know when to harvest the grapes? 

There are a number of factors, and various tests. On a simplistic level, it’s about testing the level of sugars. This gives an indication of probable alcohol level, and depending on the results, plotted over time, you can estimate when to harvest the grapes.

Of course that does not take into account weather. Warm weather can speed up the ripening process, so your sugars increase quicker. And of course vice versa if it is cooler. How much rain or lack there of can come into play as well.

Then there are the grape predators – birds, wasps and a variety of other insects. We certainly have had our share of those. So a lot of time goes into putting up scare CD’s, scarecrows, even imitation flying hawks. All to try and keep the birds at bay. But there is little one can do about the insects.

When Pumpjack was away in Mexico making wine for a winery there, I had my first experience of measuring sugars on my own. It was a little stressful as I was getting my instructions from a long way away, and generally with a 24 hour delay in question and response. But as the tests progressed I had a better sense of what to do and why.

The first test I did was with a hydrometer, which looks like a very long thermometer. You collect about 10 grape bunches, enough anyway to make about 500ml of juice. Bunches are collected from the same grape variety but in various places in the vineyard, to give a better indication of how the whole crop is doing.

We had 3 varieties: Chardonnay, Pinot Noir and Pinot Meunier (a classic combination for Cremant de Bourgogne). We had so few Chardonnay grapes that year I was too cautious and did not collect enough to get the requisite quantity of juice to do the test. But with the others I did manage.

Once you collect the grapes, you squish them (this is were feet can come into it, but I used fingers and a sieve). Then you pour the juice into a tall beaker and float the hydrometer in the juice. The reading is taken from the mark on the hydrometer where it meets the top of the juice.

You then repeat this test every few days and record the changes in the readings. They should increase each time and it helps you plot when to anticipate your harvest.

The trouble with relying solely on a hydrometer is it is not the most accurate way to read the sugars. Results can vary quite widely, so it takes quite a lot of readings over quite a long time to achieve some sense of result. 

The year we didn’t have enough Chardonnay grapes to spare to conduct this type of test repetitively, it spurred us to invest in a refractometer. They cost about 60€, but it is money well spent in my book. It allows you to test individual grapes rather than whole bunches.

You can either test each grape, making notes as you go along. Or, my personal preference, collect about 100 grapes. All had to be of the same variety, but making sure they were from varied locations in the vineyard as well as varied locations on the actual bunches. Again, I squished them, and then I put a couple drops of the juice on the refractometer and it gave me my reading.  Much easier, much faster, a bit more accurate, and I could do it all whilst in the vineyard.

As I did each test I could clearly start to see the fairly consistent rise in the sugars. I started to panic less about Pumpjack’s delayed return to France. In fact his return timed out beautifully. He arrived back with the anticipation that harvesting the grapes would begin in a week’s time ~ assuming the birds and the bees didn’t get to everything first.  Time to make more scare CD’s.

More about seasonal work in the vineyard:

What we watch for in summer in the vines: Summer in the vines if officially here (July)

Grape Harvest in the Vineyard : The Vendange (September)

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As wine makers ourselves, we are always on the search for interesting and unique and particularly French wine items for our vintage and antiques shop. Here’s a taste of some of the things we have found:

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