nothing natural about a vineyard. The grape vine's natural habitat is
woodland, where it grows as a climbing plant that uses trees and
bushes as a support. Left to itself, and given an adequate water
supply, a vine will send out long, fast-growing shoots that search for
something to climb up. The climbing shoots attach themselves firmly to
the support plant by tendrils. Where a shoot touches the ground, it
has the capacity to develop a new root system. And in its woodland
habitat, a vine will produce relatively few small bunches of rather
tart grapes that would make pretty thin, acidic wines.
In this sense, the most 'natural' vineyards are probably those that
involve training the vines on pergolas, as is still the custom in
Portugal's Vino Verde or Italy's Veneto regions. Here, individual
vines are grown up a wooden support some distance from the ground
(ladders are needed for the harvest). But the grapes that are produced
by this method aren't particularly good.
More modern methods of growing grapes, in close-spaced rows on wire
trellising, take advantage of the fact that making the vines struggle
generally results in better quality grapes. It's a bit like people.
Place someone in a near-perfect environment, giving them every comfort
and all that they could ever want to satisfy their physical needs, and
it could have rather disastrous consequences for their personality and
physique. If you take a grapevine and make its physical requirements
for water and nutrients easily accessible, then (somewhat
counterintuitively) it will give you poor grapes.
Forgive my anthropomorphism, but this is because the grapevine has
a choice. Given a favourable environment and it will choose to take
the vegetative route: that is, it will put its energies into making
leaves and shoots. Effectively, it is saying, 'This is a fine spot,
I'm going to make myself at home here'. It won't be too bothered about
making grapes. But make things difficult for the vine, by restricting
water supply, making nutrients scarce, pruning it hard and crowding it
with close neighbours, and it will take the hump. It will sense that
this is not the ideal place to be a grapevine. Instead of devoting
itself to growing big and sprawling, it will focus its effort on
reproducing itself sexually, which for a vine means making grapes.
And this is just what the best vineyards do. Nutrients and water
are necessary for growing vines, but they will be hard to find.
Planted close to its neighbours, the vine will have to send roots deep
into the subsoil in order to scavenge enough resources. This will have
the added benefit of ensuring a steady but restricted water supply,
ideal for producing high quality grapes. Another benefit of making the
vine struggle a bit is that yields will be lower, and although the
reasons aren't fully understood yet, lower yields generally result in
These principles seem to be borne out by a new technique, called
partial root drying (see here
for an example). Normal irrigation techniques can make vines too lazy
to produce top quality fruit. However, a new technique developed
jointly by British scientists from Lancaster University and
viticulturists from the University of Adelaide takes advantage of the
fact that struggling vines concentrate more of their energies on fruit
production. Partial root drying involves irrigating one side of the
vine while letting the roots on the other side undergo a period of
drought (lasting from 5-14 days). Then the irrigation is switched to
the other side, and the cycle continues so that at any one time part
of the root system is always under water stress. This causes the roots
to send signals to the shoots (the plant hormone abscisic acid is
involved) that tell them to concentrate on grape production, not
growing leaves. As well as improving grape quality, this system also
reduces the amount of water used by the plant. An added bonus is that
thereís no loss in yield, a trade-off that normally has to be made
with enhanced grape quality. It sounds almost too good to be true.
But, as with people, while a little stress can be beneficial, too
much is bad. In hot climates, once temperatures reach a certain level
the grape vine shuts down. Grape development and vegetative growth
stop. So somewhat counterintuitively grapes can actually take longer
to ripen in very warm areas (such as Spainís central plains) than
they do in cooler climates where the vines never undergo this shutting
down through heat stress. Thereís also evidence that too much
environmental stress can make vines more susceptible to diseases, too.
As in many walks of life, balance seems to be the key.