May 2009 Douro Insider

The sunny weather and rallying temperatures that brought a last minute burst of good weather right at the end of April continued a little way into May, although not very far. There was indeed a fine and hot start to the month but, once again, this was in part brought on by a very dehydrating vento soão (easterly wind). This meant more bad news for the vines but it was mercifully short-lived. Then after the first week was over the pattern changed more towards the unsettled with some promising clouds appearing in the skies. Unfortunately they delivered very little, perhaps one or two relatively light showers, but at least temperatures were noticeably cool at night and early in the mornings. By mid-month things became windier again, but by this stage it was predominantly from the western quadrant which is the more usual source of prevailing weather.

The uncertainty cleared up before long and the rest of the month settled down into a pattern of basically sunny weather but with quite cold nights still. Had it not been for some evenings dropping below 10º C even into the last week of the month, the calm and clear skies and warm days would have been perfect for flowering. The only slight hiccough came with a thundery penultimate weekend that was characterised by sticky, brooding clouds and occasional sudden, localised and fairly quick showers. Unfortunately they brought nothing significant in terms of actual millimetres of precipitation, however. Once this had passed by we suffered a very hot and sunny last few days of the month. In the Douro we had the hottest spell of the year so far, with daytime temperatures in excess of 35º. To our relief, the aforementioned up-river winds kept blowing strongly during the late afternoon and this did much to bring temperatures down to comfortable levels at the end of the day, and also widened the range of the mercury’s daily fluctuations. In Porto there was no such luck. The winds there were (unusually) easterly and pushed temperatures up into the 30ºs which is relatively rare for this time of year. Combined with the higher humidity on the coast this made for a couple of rather uncomfortable days.

On a broader scale, meteorologists suggested that this heat might be related to the end of La Niña, an effect which (as we mentioned last month) brings cold water to the surface of the oceans and thereby also cools land temperatures. Could it signal the start of the much-lauded ‘barbeque summer’ that has been promised for northern Europe? Certainly it has been suggested that we are to expect fine weather for three reasons, the first of which we have just covered. In addition there is high pressure predicted over Britain and Europe (which normally keeps the skies clear and therefore also has a tendency to keep away rainfall) and we are expected to feel some knock-on effects from a warm phase in the tropical Pacific region. It has been mooted that the UK will benefit in particular, with temperatures there much closer to those of Southern Europe, but the general threat of hot and dry summer is still of much concern to us here as the drought looks set to continue.

The facts from Pinhão are best described as woeful. The entire month brought a miserable total of just 12 mm of rain – compared with the average monthly sum for May of 54 mm this is less than a quarter. There were really only two days on which precipitation of any significance fell, with about 5 mm each. This is a meaningless amount which did little more than temporarily settle the dust, if that. It would not have had any kind of penetration into the rootzone of the vines whatsoever. As if this was not bad enough, the average temperature was well above the mean, coming in at 19.1º instead of the 17.5º that might have been expected. We had three days over 35º, with a monthly peak of 36.6º being reached on the 30th. May is often a month of extremes; experience in the Douro has shown us that winter usually turns to summer at some point between the 1st and the 31st of this month and this year was no exception, with just 6.8º being registered on the first night. As far as the spring goes, that was it.

Our usual rainfall graph predictably shows an ever-widening gap between the stagnating orange line (where we are) and the red line (where we should be). The cumulative rainfall for this year currently stands at 239 mm whilst the average for this stage is just over 320 mm, making us 26 % below. One factor that we should not overlook in these monthly reports is that data from Pinhão has always been used as our reference value. This is done for two reasons – firstly because Pinhão is located in a conveniently central spot so as to be about as representative for the Douro region as any one place can be, and secondly because it is where we have the largest climatic data series, with daily records going back to 1967. What this often means is that it is easy to forget that Pinhão is by no means the driest part of the Douro. Whilst it rains considerably less here that it does in the Baixo Corgo, for instance, vineyards in the Douro Superior are suffering an even more severe drought. Some quintas there have received less than 200 mm so far this year.

One of the interesting side effects of this very dry spring is that it appears to have accelerated the phenological cycle of the vines by some degree. In spite of the fact that in general shoot growth is very much reduced for this stage of the year, flowering has come early. It seems almost as if the vines are aware of the water shortage and in response they are speeding up their cycle in order to reproduce as quickly as possible before conditions worsen further as the summer heats up. There has predictably been no need for despontas (shoot trimming) so far this year, but this is not in itself anything unusual at the end of May. The ‘average’ date for flowering this year was the 20th May which is a little earlier than normal, and five days earlier than last year. With one or two localised exceptions the flowering period was relatively homogenous, which is usually considered to be good news. It progressed smoothly into fruit set just six days later (on average) which therefore came nine days earlier than last year. Indications so far are that the good weather has favoured flowering and there are generally not too many problems with desavinho (poor fruit set). The one exception to this would be the Tinta Barroca which has definitely suffered worse than usual this year, especially on the higher ground. Yields will be down somewhat for this variety. Rumours from the western end of the region also indicate that the Tinta Roriz has not fared well in the Baixo Corgo although quite frankly most people would agree that a bit of desavinho in the Roriz could only be a good thing, perhaps lending the wines a greater degree of concentration than they normally show from that subregion.

Most of the major jobs undertaken in the vineyards in May are rather similar to April’s – revolving around the need to control the vegetation of the vines (canopy management) and anti-fungal treatments. As these were discussed at some length at the time, no more shall be said on the matter. This time of the year, as the spring begins to dry up and the first flush of summer heat is felt, is also the ideal moment for a reappraisal of the weed situation. Whilst the main campaign is carried out in the period immediately preceding budburst, the pre-emergent herbicides applied then might be starting to lose effectiveness by now (especially if the spring has been wet, which is obviously not the case this year). Thus we normally spend a couple of days checking over the quinta for any spontaneous weed growth that might have sprung up since the end of winter, especially focusing on the taludes (banks), and carefully target the offending plants. The fact that the weather is sunny and the weeds are photosynthesising well ensures their rapid demise, and the general drying of the soil means that the demise is permanent. Alternatively, or often additionally, ploughing between the rows serves the same purpose on the flat parts of the vineyards.

The only exception to soil mobilisation would be in the unfortunate situations that there is an outbreak of grama (couch grass). Since ploughing spreads its roots and aggravates the problem, herbicides are the only way to deal with it. Some manual talude clearing is also employed to leave the patamares looking tidy before the summer.

On a similar note, it is important not to let the olive groves become completely overgrown. When time permitted, various quintas took the opportunity to clean under and between the trees in the olivais. With the increasing prevalence of cover cropping many quintas now possess agricultural mowers as a way of cutting back the grass. These can of course also be used as an ecological alternative in the olive groves, and they even have a hydraulic mechanism allowing the cutting head to be offset laterally to either side, making it possible to mow right up to the trunks of the trees. This is, of course, when they aren’t being used for the cover crops. Since these had basically finished flowering by the end of the month, ensuring a good seed bed for next year, we started to cut them close to the ground to ensure that they do not spring back again before the first autumn rains. This material will now remain on the soil surface during the summer as a protective mulch, shading the topsoil from the summer sun and reducing the desiccating effect of the wind.

That fairly much covers most what we were up to in May, except for the new plantations. There, britadeiras (rock crushers) were out at a couple of quintas, smashing up the rocks that had previously been piled in the mid-row and thereby giving the tractors (and indeed the vineyard workers) a smoother passage through the vineyards. After this work was done, the caldeiras (depressions at the base of the vines) could be (re-) opened, and this of course made watering possible, which was also necessary given the lack of rain.