Port anD the Douro 67graFting, training anD Pruning
Ever since phylloxera ravaged European vineyards towards the end of the nineteenth century,
nearly all Vitis vinifera varieties have been grafted on to phylloxera-resistant American roots
(see page 28). The choice of rootstock is important, to ensure compatibility between the scion
and the root as well as the soil and the environment.
In the Douro a rootstock known locally as Montícola (rupestris du lot) proved to be the
most popular because of its ability to adapt to the poor schistous soils. This has subsequently
been found to promote too much vigour in some varieties, aggravating the recurring
problem of excessive vegetative growth combined with poor fruit set. Touriga Nacional
was particularly badly affected. Since the 1950s, hybrids of berlandieri with riparia (420-A,
SO4) and berlandieri with rupestris (R99, R110, 1103 P and 196-17) have been introduced.
The best of these seem to be the R110 and 1130P, both of which are resistant to drought and
help to limit the natural vigour inherent in certain Douro varieties.
Until the 1990s, American rootstocks were planted directly into the newly prepared
soil where the vine would be allowed to establish itself before being cut back and grafted
with a vinifera variety. Given the fairly arid conditions in the Douro, this method –
known as field grafting – resulted in an unacceptable level of failures (over 20 per cent
in some places). As vines are only permitted to produce grapes for Port in the fourth
year after grafting, field grafting delays the first commercial crop of grapes by a year.
Nowadays most Douro vineyards are planted with pre-grafted vines, often bench-grafted
(i.e. grafting prior to planting) in France. These are considerably more costly and require a
higher initial investment but reduce the number of failures to between 5 and 10 per cent.
Bench-grafting actually saves time as well as money, and also makes for a stronger, more
regularly shaped vine that adapts more readily to mechanisation. Many shippers are now
using plastic grow tubes that protect the young vine and foster growth. Adrian Bridge,
Managing Director of the Fladgate Partnership, calculates that vine mortality has been
reduced to as little as 2 per cent.
When the ground has been excavated, ploughed and tilled, planting takes place at the
end of the winter or in early spring when soil water reserves are usually fully replenished.
Slim posts hewn from local slate were traditionally driven into the ground to support the
row of vines, but the brittle nature of the slate coupled with increasing mechanisation has
led to treated wood or steel being used as a replacement. A new vineyard will normally
undergo training and trellising in its second year.
Unlike Australia and New Zealand, little research has yet been undertaken into the
implications of vineyard canopy management; however, there is now a general view
that a higher vertical training leads to better photosynthesis. Two methods of training
are commonly used. The first is an imperfect form of double guyot in which the vine
is pruned back to leave two shoots with around ten buds per plant. Nuno Magalhães,
Professor at UTAD, believes that the traditional guyot makes vines resistant to drought
and increases vine longevity. He laments that few people in the Douro know how to
prune to guyot any longer.