Weather extremes are not uncommon in the Douro Valley and the arrival of spring this year was a perfect illustration of that. The period of the vines’ winter dormancy, during which the plants have minimal metabolic activity (they’re literally asleep) was fractionally warmer and drier than average and the spring followed a similar pattern — hot and dry. However, the season kicked off in the Douro with abundant snowfalls on March 23rd that shrouded the region’s higher altitude vineyards with blankets of snow. Widespread frost also affected the Douro Superior on the 25th. The chill, though, was short-lived and temperatures soon swung back up in April; it was the third hottest month of April of the last 40 years.
As well as unseasonably warm, this spring was also very dry due to the overall lack of precipitation. March did manage approximately half the monthly average rainfall but April was remarkable for the near total absence of rain; just 2.6mm was recorded at Quinta do Bomfim where the average for the month is 46.9mm. It was in fact the driest month of April since official weather records began in Portugal in 1931. Precipitation in May was closer to the mean, helping to raise soil moisture levels. For the spring as whole (March through to May), rainfall was approximately half the thirty-year average.
As a result of these climatic conditions, bud-break, which marks the beginning of the vine’s vegetative cycle, began between the 8th and 10th of March (Touriga Franca at Quinta do Bomfim), very similar dates to 2016 and approximately a week earlier than average. Although the start of this phase then slowed significantly, the vegetative cycle soon picked up and advanced at a very fast pace.
Flowering occurred three weeks earlier than in 2016, beginning between the 4th and 5th of May and was two weeks ahead of average dates. By the end of the month the cycle maintained this precocity with formed bunches well visible in the Touriga Franca.
The upside of the hot and dry conditions has been the very low disease threat levels (downy and powdery mildew), in sharp contrast to the comparable period in 2016. Vine canopy management was a priority during the final stage of the three month period, involving vine hedging (despampa), shoot topping (desponta) and shoot positioning (ampara) — guiding the shoots through the trellis wires. Weed control along the soil top cover also required great attention given the extra vigour of plant growth encouraged by a combination of the high temperatures at the start of this cycle and the availability of water in the soil, which although limited was sufficient to stimulate such growth.
At our Douro properties, new plantings were concluded at Quinta do Bomfim with 7.5 hectares of Alicante Bouschet, Touriga Nacional and Touriga Franca; Quinta da Macieira in the Vilariça Valley with 8 ha of Alicante Bouschet; Quinta dos Malvedos with 7 ha of Touriga Nacional and one hectare of top grafting (see definition below); Quinta da Telhada with 6.5 ha of Touriga Franca; Quinta de Roriz with 1.5 ha of Touriga Nacional and 1.9 ha of top grafting and finally Quinta da Perdiz with the planting of 4 ha of Touriga Nacional. This brings the total planting for this year to 34.5 ha of new vines and 2.9 ha of top grafting (changing over to Touriga Franca).
Top grafting (sobre-enxertia): “Changing the fruiting vine variety of a mature vineyard by inserting a bud of a selected variety in each vine, but retaining the established root system.” (source: The Oxford Companion to Wine, Fourth Edition, 2015).
At our principal grape variety library, established at Quinta do Ataíde in 2014, studies were carried out on the dynamics of bud-break and flowering for each of the 53 varieties planted and similar studies were also made at the Quinta do Bomfim Grape Variety Library.