June 2010 Douro Insider

Those lucky enough to combine the holiday on the 3rd with a ponte (bridge day to make a long weekend) enjoyed fine weather over the short break but were then met with a grey and drizzly welcome as they returned to work after the first long weekend.  It was decidedly cool and a fair amount of rain followed.  To further complicate what was already turning out to be a difficult growing season, the all-day downpour on the 9th brought a renewed risk of disease and a number of overcast days did not help the vines much either.  This ugly patch coincided with newsworthy flooding in places as far-flung as Turkey and Poland so it was clearly part of a Europe-wide weather system.  Conditions warmed and brightened once it had passed, but not for very long since by the middle of the month it had turned cooler again and we saw a return of the clouds for short spells of the day.  Some wind picking up, especially in the afternoons, definitely gave the impression that the atmosphere over the Mediterranean basin was not settled, and the French surely felt the same way when flash floods on the Provence coast caused by the heaviest rainfall for nearly 200 years took at least 25 casualties.  The Douro itself was hit by a thunderstorm on 18th that dumped yet another significant load of water on the hillsides.

The ups and downs continued.  The thunderstorm seemed to clear the air and it was replaced by a high pressure system bringing good weather for a week or so afterwards, up to and including and the S.  João holiday.  Then, as so often seems to happen around the end of June, it once again turned somewhat unsettled with overcast skies and several spots of rain.  And finally, in the very dying hours, June finished on a real high with extremely hot temperatures tempered by thundery air.  In general the month was characterised by hot days and cool nights which ensured that dews fell regularly in the vineyards and, occasionally, just when everything seemed to be under control, along would come a thunderstorm bringing another downpour.  These last two factors meant that there was always plenty of humidity around the vines and so special care was required with preventative treatments against fungal diseases.  So far we have erred on the side of caution and as a result the grapes are looking fantastic at the moment.  It pays to be careful in viticulture.

In Pinhão the total rainfall for the month was 72 mm which is more than double the average of 33 mm.  That said, the majority of it fell on only three wet days but frustratingly they came with an interval of around 10 days between them.  Given that the majority of fungicides offer little protection beyond 12 days it can be seen that the viticultural month was not particularly easy.  This apparent return to the pattern set by the sodden winter means that we have therefore had above average precipitation for eight of the last nine months.  Our current cumulative total for the year now stands at 489 mm, nearly than 40 % higher than the 355 mm that would be expected.  There was, however, a wide range of precipitation values across different parts of the Douro which illustrates how localised these summer thunderstorms can be.

Records show that temperatures in Pinhão were around half a degree above average too, with a monthly mean of 22.2º C.  This makes it the sixth month out of the last eight (or ninth over the last year) that has been warmer than the mean.  In terms of absolute values, our weather station at the heart of the Douro registered a maximum temperature of 36.9º making June just a shade short of 100º F at its hottest moment.  This milestone was exceeded in the Douro Superior.  By comparison, the minimum was relatively cool – a fraction over 10º.

The challenges posed to the discerning viticulturist this month were not unlike those of last.  In fact, in many respects June told almost exactly the same story as May; it was all about canopy management and anti-fungal treatments.  These two issues are more closely related than many people might think because a well-trained and open canopy can be as effective in terms of controlling fungal diseases as is the use of chemical sprays.  Sunlight and airflow combine very effectively to dry out the interior of the canopy affording the vines some considerable protection against the two sorts of mildew.  Furthermore, of course, sprays will not penetrate far into an overgrown and unnecessarily dense hedge of foliage, rendering treatments all but useless.

The main difference between May and June was that this month the majority of the quintas started seriously tackling the shoot trimming, or desponta.  The timing of this important activity is critical and depends much on the development of the vines during the growing season.  There is one essential condition which must be met before desponta can even be considered, and that is that the primary shoots attain sufficient length for their tips to emerge comfortably between the top pair of trellis wires.  Some 20 to 30 cm over should be adequate.  This means that the fruitful shoots are held vertically, and the bunches are therefore not hanging out sideways into the mid-row space.  Were this to be the case the fruit would obviously be damaged or even chopped off completely by the trimmer.  The presence of shorter and more horizontally growing lateral shoots in this space is no problem as they do not carry any grapes.

There are a number of critical effects that this trimming has on the vines.  Firstly, and most obviously, it permits the physical passage of man and machine through the vineyards with ease.  As has been mentioned before, it also improves spray penetration, making treatments more effective.  Additionally, it will expose the bunches to sunlight to some degree which is important for ripening.  When carried out at the right time, just as the water reserves in the soil are starting to dry out, it should also bring shoot growth to an end.  It is important that this occurs at veraison or soon afterwards as we are obviously interested that from this point onwards the vines are channelling their energy into producing sugars to ripen the fruit rather than in growing more leaves.

By removing the main growing tips desponta may encourage the growth of lateral shoots in medium to high vigour situations.  This is usually considered to be beneficial, up to a certain point, as the new leaves that grow on these lateral shoots will be fully photosynthesising adult leaves in the run-up to harvest, responsible for sugar accumulation in the grapes.  Despontas can be carried out by hand (using secateurs) in the non-mechanised vinhas velhas, or the equivalent effect can be achieved there by simply rolling the shoot tip horizontally along the top wire.  The suppression of apical dominance at the top of shoot effectively brings to an end its time as the main nutrient sink of the vine, and the bunch takes over.

Another of the activities that took up a fair amount of time this month was what the caseiros drily refer to as ‘mowing the lawn’.  There was still plenty of grass to be kept down in the cover crops.  With any luck this too should find its expansion checked by removal of the growing tips and a general drying out of the soil.  Conditions this spring also meant that there was more weed growth than we would have liked and, time permitting, some of the quintas were able to start on the spot application of summer herbicides, particularly on the taludes between the terraces, and occasionally under the rows of vines.  The fact that the wet part of the year is theoretically nearing its end should mean that the vineyards remain clean now until after the harvest.

In some of the new plantations we were able to get to work on such jobs as opening up caldeiras for the rootlings that were planted this spring.  These depressions at the foot of each vine are essential in the first year or two.  Not only do they make the best of any naturally falling rain, but they will also be used a number of times over the course of this summer as the vines are watered by hand.  And whilst on the subject of new vineyards, June was the month that saw the wires and posts installed in most of this year’s new plantings.  They will not be used until next season but completion of the trellis is a precondition for receiving the subsidies offered for reconverting old vineyards into something altogether more modern and efficient.