Heat wave in Europe

The massive heat wave in Europe is pretty alarming. Chiefly, because there have been a huge spike in heat related casualties; but as it pertains to this forum I am pretty curious about the vines there.

Rioja and Rivera Del Duero for example are already seeing days over 40c (104f) and looks like more to come. Anyone in the area that can comment on the grapes/vineyards?

  • This is week is higher than normal for Rioja, which usually has highs in the mid-90s, not in the 100s. Heat spikes as high as 115+ in Sonoma or Napa are not uncommon.  Better that it is not happening right before harvest; I think the vines should recover fine at this stage in the season. ?

    Here you can see the typical temperatures for Haro, Spain over the last ten years (based on monthly average high, not daily record). 

  • Unfortunately I'm not in Spain at the moment, so I can't comment on the specific situation there, but I can speak generally to the risks of early season heat events. 

    I'm guessing that the vines in Rioja and Ribera have probably gone through flowering but are not yet at veraison. While the high temperature is certainly concerning, as Geoff mentioned, early season heat spikes are lower risk than those that happen closer to harvest from a fruit quality perspective. The fruit is not susceptible to dehydration at this point or some of the chemical reactions that can compromise the flavor and color of almost-ripe grapes. There is some indication that temperatures over 35C can reduce fruit set, so for regions still going through flowering, yields may be a bit lower.

    The main effect at this point in the season is that temperatures over 35C will halt all of the vine's metabolic processes. Photosynthesis and respiration stop, effectively freezing the vine's development until the weather cools off, so veraison and harvest timing may be delayed. Sunburn on the fruit can be an issue, but bush vines should be less susceptible to this. The biggest concern is if leaves get scorched, development could be slowed down further. 

    Grapevines (unlike grapes) are hardy. Let's just hope those conditions don't persist later in the growing season!

  • We're going to hit 39 in Priorat, but you know, it's a dry 39 :)

    This isn't atypical to be honest and while the vines could shut down, this early on, it's not a massive issue, especially if it's just for two days as is currently predicted.

    The bigger issue is if there are continued spikes like this and we end up with a 2011 vintage which was very unbalanced. Too early to tell though.

  • I understand that phenolic development is happening in this phase of growth, and hot weather can lead grapes to produce more of almost all of the phenol compounds. Should we expect bigger tannins and darker colors in the [red] wines from a vintage with heat spikes this early? 

  • I am visiting Belondrade in Rueda today and will be in the Ribera y Rueda area for another two days. I don't think they are near veraison but will check on the vineyards for you.

  • I just returned home from spending the last week in Bordeaux and Germany and I have to say that it was HOT. Many of the vintners were not that concerned at this heat wave occurring at this stage of the growing cycle - much more of an issue if this were to occur after veraison. 

    Irrigation is being employed in areas with dry soils and more delicate vines. Careful canopy management is needed to provide enough shade for the grapes. Some vineyard work is not being done because the vines are too sensitive. 

    One of the conversations being had was that climate change is real and questioning if this is the new normal. There are many experiments occurring to try to combat some of the issues of heat and drought including experimenting with other grape varieties in Bordeaux. 

  • Shouldn't have happened. Was stored improperly.

  • It's 104F in Rueda right now. I looked at a number of bush vines, head trained, and single and double cordon and they are all looking good with no visible signs of stress. The grapes are still hard and the size of ball bearings. I met with Jean Belondrade Lurton at Belondrade and he said it may slightly advance the ripening process but there is no need for concern. It will most likely get hot again in July and August. Most of their vines are dry-farmed and they don't pull laterals (occasionally leaves to open the canopy) so the grapes are largely shaded. In general, it is hot and windy with a large diurnal shift so the disease pressure is low and it is fairly easy to farm organically and without irrigation. 

    Edit to add: they also don't cut (hedge) the shoots. I have seen photos taken today in France of wilted vines that had been cut earlier.

  • Pretty much the story of every compost, mulch, and fertilizer fire...

  • Geoff thank you for some of this data. All these responses are fantastic and very illuminating.

  • The short answer is, there's a good chance that this could be the case, but it's too early to tell.

    As you mentioned, pre-veraison is an important time for phenolic development. The vine is making tannin and some of the precursors that will be be converted into anthocyanin (color) beginning at veraison. While tannin production is stimulated by higher temperatures, production of these precursors is more closely tied to sunlight exposure than heat (since these compounds act like "sunscreen" for the the vine). 

    Ultimately, the concentration of these compounds in wine depends largely on berry size which depends on the water status of the vine. High temperatures can induce water stress, limiting berry size, but this is not always the case, for example, if the spring was very wet or if irrigation is used generously.

    The weather after veraison is really important too. Color is degraded by heat, so a warm end to the summer could ultimately reduce color. An important concept that's been getting more attention recently is the extractability of tannin. There can be a high concentration of tannins in the grapes, but low extractability, resulting in lower concentrations of tannin in the wines. A few researchers are looking at this, it seems that the weather after veraison is important, but there is still a lot that we don't understand. 

  • Beki, is irrigation allowed in Bordeaux and Germany?