After a pleasant end of February, the start of a new month immediately brought a return of the cold weather. Temperatures were very low for the first few days of March, and sub-zero in some places at night. The morning frosts thus made a crisp comeback, especially on the high ground. This is always slightly worrying for a viticulturist, when the vines are getting so close to budburst, but the cold weather slows down the awakening of the vines and prolongs dormancy as a form of natural protection. In the end the cold spell was short-lived, and it was still very sunny nevertheless. As so often seems to happen, we were hit with some pretty bad weather over the long first weekend (it rained on the Carnival parade) and then stayed cloudy and drizzly for another couple of days. There was a brief up-perking around the 10th before conditions reverted to uninspiring and wet. It also remained cold, with some hail coming down in the Alentejo and, surprisingly, there were even snowfalls in Madeira getting on for mid-month.
Things took a turn for the better around the 18th and the skies cleared nicely. For a while it was sunny and surprisingly warm, genuinely feeling like spring had come after February’s retrospective false start. It continued like this for several crucial days before reverting to what is best described as ‘changeable’. It was somewhat cooler, a bit windy, sometimes sunny and a little rainy too, eventually deteriorating into simply cold and wet, pretty much for the rest of the month. The only exception was the very last day of March, which in some places turned out to be the warmest day of the year so far.
Our meteorological data shows that it was not really very hot at all, peaking only in the mid-20ºs at most quintas and quite a bit lower on the higher ground. Even the properties that escaped the frosts at the start of the month had absolute lows that were close to zero. The average temperature in Pinhão was only 11.6º C which is a fair bit short of the mean for March, standing at 12.3º.
In terms of precipitation the balance of the month, perhaps surprisingly, showed it actually to have been a touch drier than average. The fact is that, although there were several wet days, the rain was mostly of a low intensity. Prolonged drizzle can easily leave one with the erroneous perception of high precipitation, and that was perhaps the case in March. Pinhão had just 37 mm of rain – a significant amount below the long-term mean of 52 mm. Since March was the third consecutive month with below-average rainfall, the cumulative total for the year obviously remains under what might be expected. As can be seen on the graph below, the actual figure currently stands at 167 mm, just behind the 215 mm average value for this stage of the year.
On a more general note, the Instituto de Meteorologia published a review of the three months from December to February, and pronounced it to have been a slightly colder and wetter winter than average for the country, characterised by some extreme weather phenomena. It was therefore the third consecutive winter of below average temperatures in Portugal and indeed, as our figures also show, in the Douro too.
Impending budburst is the main factor that conditions work in the vineyards in March, with virtually every job that is undertaken needing to be carried out before the easily-damaged shoots emerge. Some of the older vineyards which are still trained to a Guyot system may be entering the very last phase of pruning, erguida. This involves arching the loose canes and tying them down onto the fruiting wire. A similar process is carried out in young vineyards, generally those going into their fourth year, only the canes will be wrapped flat instead of arched, and thereby form the permanent cordon of the vine. Normally the buds on vines in the first few years of their existence burst a few days earlier than those on older plants.
Trellis maintenance is usually carried out at this time of the year too as clearly the period between finishing pruning (once the canes have been stripped off the wires) and the appearance of the new shoots is the only practical time at which the trellis is completely accessible. Broken posts (or stones, in the older vineyards) will be substituted, missing staples replaced, and the wires will be repaired and tightened in preparation for the new season. Incidentally, tightening the cordon wire where applicable obviously needs to be carried out before the canes mentioned in the previous paragraph can be attached. One part of the trellis which is particularly important to check are the end assemblies – the strainers need to be in a good condition as they are responsible for the structural integrity of the whole row of vines. If the soil is too moist, however, this will need to be delayed as tensioning the wires could pull the posts out of the ground or at least loosen them.
March inevitably marks the start of the real viticultural year, as winter dormancy ends and the vegetative cycle gets underway again. We should therefore probably turn our attention to phenology at this juncture, and it is worth noting a slightly curious beginning. In spite of the fact that the winter was cooler than might have been expected, it turned out counter-intuitively that budburst was actually somewhat earlier than usual. The average date for the principal varieties this year was the 20th March. This is five days earlier than the corresponding date for last year, and three days before our average date. Initially shoot growth was not particularly quick, in spite of the abundant soil water, since temperatures were definitely on the cool side (especially the minimums).
With everything getting underway again, one would hope to have finished planting the americanos (rootstocks) by now, and even in the new vineyards the rootlings should be in the ground by the start of April. Note that the timing of the very first budburst of a rootling is not so strongly influenced by the usual annual rhythms of nature. Since they are stored in the cold and dark, budburst can be delayed for much longer until the rootlings are planted out. The same logic applies to some degree to the canes that have been previously cut to provide semente for grafting in the field. The grafter needs the sap to start to rise in the rootstock to ensure a successful take but obviously requires that the buds on the scion are still dormant. The canes that are to be used are therefore cut earlier and kept out of the sun in black plastic bags. (Learn more about the field grafting process in this blog article.)
Grafters are always accompanied by one or two other vineyard workers who uncover the rootstock plants that are to be grafted, and then re-cover the newly-grafted vine so that the graft union is kept humid whilst it heals. Another activity that is often carried out by these other workers is a process called escava, which basically consists of pruning the roots of certain vines. The idea is to locate any vine that was grafted in the field last year and uncover the trunk down to below the level of the graft union. Any vinifera roots (that are not phylloxera-resistant) that may have grown out from the scion (above the graft union) are then removed to ensure that the vine draws its nutrition from the American rootstock. This process is obviously not necessary with bench-grafted vines as the graft union is always above ground to start with.
Although it seems that quite a lot has been going on this month, we have yet to mention another major activity – keeping the winter’s weeds in check. This will be the last chance we get for some time as once the vegetative cycle starts our attentions will be focused on the vines. There are a lot of weeds this year, mostly as a result of December’s massive rainfall which means the soil is still very damp. This job is carried out far more quickly on the vertical plantings where the mid-row space is protected from erosion by cover crops, which in turn control the undesirable weeds. As a result we need only clear a thin strip of soil immediately below the rows of vines.