June 2008 Douro Insider

For those involved in agriculture in the north of Portugal, it has been hard to know what to make of the weather so far this year.  And for regular readers, it must be becoming tiresome to read every month that things are not following predictable patterns.  Thus it may come as some relief to hear that in June it appeared that things are more or less returning to normal.  What June typically brings us is generally fair weather, dominated by hot and sunny days (although not usually featuring scorching temperatures) that might be interspersed with one or two overcast days.  There are two common features of June, however, which make it different from just a cooler version of July.  Firstly, the amplitude of the range of temperatures is normally far greater, principally as a result of relatively cool nights.  Secondly, although rainfall would not usually be expected, it is still fairly common to have one or two major downpours.  Thus precipitation figures for the month are either very low (when there are no thunderstorms) or really quite high (months with total precipitation in excess of 70 or even 100 mm are by no means unheard of).  As this talk of thunder should imply, humidity can often be high.

Moving on to the specifics of this June, what can be said? Firstly, it was one of the dry Junes, with virtually no precipitation.  This means that in all probability (unless the end of August brings a welcome surprise) the vines are going to have to make do with whatever moisture they can extract from the soil from now on for ripening the grapes.  We cannot realistically expect any significant rainfall during the summer months.  Secondly, this year’s odd rule (that the average monthly temperature values have been masking unusual fluctuations on a daily and weekly basis) still holds.  That said, these temperature swings do appear to be decreasing as one would expect as we approach the peak of the summer.

Things kicked off pretty cool, with very moderate temperatures in the low 20ºs right at the start of the month.  This corresponded with a weather front that brought severe storms and major flooding in Germany on the 2nd.  After a disappointing first week, it suddenly seemed that summer had arrived in the second week of the month.  The temperatures began to rise, and with them the sticky smell of gum cistus filled the air and was carried upriver on the warm evening winds.  The illusion was short-lived, however, and things took a turn for the worse mid-month.  There was rain on the 16th, and actual storms in the Vilariça valley.  In addition, there was a brief but a dramatic mid-month dip in temperatures which coincided with this single rainy day, a pattern repeated across the Douro.

The summer appeared to return for real thereafter with the first properly hot temperatures of the year, but this turned out to be yet another false start as we shall see in next month’s report.  In summary, June would be best described as two short-lived spells of promising weather, the second longer than the first, and both of which failed to herald the onset of summer.

Records from Pinhão show a mean monthly temperature of 22.3º C, which could reasonably be described as just a bit over half a degree above average (21.7º).  This means that four out of the six months we have had so far this year have been warmer than average (see the figure below).  And whilst June’s figure might be above the long-term mean, it is nevertheless the coolest June in 10 years.  Indeed, it might have seemed that way on the 3rd, when temperatures dropped right down to 10.8º at night, but it certainly did not on the 28th, when the mercury reached 37.3º (99º Fahrenheit).  This was one of four days on which temperatures climbed over 35º.

The weather in Pinhão also turned out to be very dry – the total precipitation (4 mm) is negligible, representing about a tenth of the average.  It has been the driest June since 2001, which had no rainfall at all.  This means that the gap between the current total for this agricultural year and the mean cumulative total closes again, with all the progress made in April effectively cancelled out.  The total precipitation so far this year is now almost exactly the same as the expected value (see the figure below).  It is interesting (though quite worrying) to point out that rainfall has been below average for 10 out of the last 12 months.  In other words, the last calendar year has brought just 511 mm compared with an average of 675 mm.  So whilst the graph might not look too frightening it is worth remembering that we are still trying to recover from a long-term rainfall deficit going back beyond the scope of the numbers presented here.

One thing that can be said for sure about the cumulative effect of this year’s slightly bizarre climatic patterns is that it has been a little upsetting for the phenological cycle of the vines.  Budburst was really quite early, flowering was a touch late, and fruit set was very late.  Our ‘official’ date for set puts it at the 4th June (a fortnight later than last year) but the real worry is that this date came about ten days after flowering.  Sooner would have been much more auspicious.  In part the problem was due to the overcast conditions during the period of flowering and fruit set that stretched out the whole process for longer than desirable.  As it turned out, this led to considerable heterogeneity in the vineyard that makes it very hard to give a precise date for fruit set, especially as some plants had both set bunches and unopened flowers in attendance at the same time.

As often happens, this means that the fertilisation of the flowers does not run smoothly, and one of two things might occur.  What with England being a country with little viticultural tradition, the English language is somewhat vague when it comes to the technical terms, tending to use cumbersome phrases such as ‘poor fruit set’ which sheds little light on the issue.  Likewise, the Portuguese generally treat everything as desavinho which again is not totally accurate and can be misleading as to the exact cause of the problem.  Perhaps the best thing to do is to use the French terms.

Coulure (correctly translated as desavinho in Portuguese) is when some of the flowers are not fertilised and therefore do not develop.  They simply drop off the bunch (we call this ‘shatter’ in English).  Note that this is a perfectly normal process and on no occasion does every flower on a bunch turn into a berry (there would never be room for them all).  This shatter would only be considered a pathological condition if it was excessive, and that is why we use the term desavinho only when fruit set is clearly substandard.  This was fortunately not a significant problem in 2008.

The second possible cause of ‘poor fruit set’ is due to a slightly different condition which only becomes apparent some time later on.  It is called millerandage in French, bagoinha in Portuguese, and this one even has an English equivalent (albeit one that sounds like it was invented by a foreigner): ‘hen and chicken’.  What this seemingly meaningless term is supposed to describe (‘hen and chick’ would be more intuitive) is that some of the berries on the bunch, although fertilised, still do not develop properly.  These grapes are born without pips, yet it is the seeds which produce the hormones required for normal berry growth.  Thus after a couple of weeks many of the berries (the ‘chickens’) are stunted in size, with very retarded development.  These will never achieve a respectable diameter, nor ripen properly.  The other berries, the ones with seeds, develop normally.  As would be expected there may be some issues here with regards to quality, although many claim that the underdeveloped berries add refreshing acidity and complexity to the wine.

The principal reason that this potential problem was not detected earlier (indeed, last month’s report suggested that perhaps we had been lucky to escape without worse losses) is precisely that it takes time for the difference in size between the hens and the chickens to emerge as the berries grow.  We cannot yet make any qualitative predictions regarding the harvest since the these berries could still dry up and drop off to some degree during the summer, or they may remain clinging to the stalks in the destemmer and thereby be expelled from the crusher untouched.  On the other hand, a reduction in the total crop weight could well represent an improvement in aroma concentration within the remaining fruit.

June is a reasonably busy month in the vineyards, but little is different from May in terms of the specifics.  Control of vegetative growth and control of disease are the two overriding concerns, and so the first jobs undertaken everywhere were the time-consuming trinity of canopy management: shoot thinning, shoot positioning and shoot trimming (this latter activity being carried out both mechanically and by hand).  Once the hedging was in order, the vines still needed plenty of attention because the weather meant that the risk of powdery mildew was ever-present.  A light dusting of sulphur was therefore applied during the course of the month.  Between them, these operations made up virtually the entire roster of vineyard activities in June.

The vines were not the only plants that had been growing vigorously all throughout June.  The flourishing of weeds during the spring meant that and in many places the banks between the terraces were beginning to develop a scrubby aspect.  These light infestations can easily be cleaned up manually using hoes or strimmers rather than by the application of herbicides.  With the hot and dry weather that we can expect from now on, this should be more than adequate to ensure that things look neat and tidy until after the harvest.  Likewise, on the flat ground of the mid-row the ecological way of dealing with these problems is by soil mobilisation so ploughing was also undertaken at a number of Douro quintas.  The only different activities going on in the region took place in the newest vineyards (those planted earlier this year).  These recent plantings were being hand watered as high temperatures and desiccating winds would obviously increase the percentage of failures if the rootlings were to be ignored.

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