During my and Greg’s emerging wine region project on the Canary Islands, one of the most curious facts we learned about was the unique trellising method that is used on the islands. Centuries ago, locals there developed a signature, horizontal grapevine braiding technique called ‘el cordon trenzado,’ or the braided cord. The longest cordon trenzado vine alive today stretches over 80 feet, and some vines in this braid are thicker than a child’s wrist. Since fruit only grow from the ends of these long tresses, this design was useful in the past because the vines could be picked up and moved to make room for planting other crops like potatoes.
I found images of these ancient,
rapunzel-like vines to be enchanting and imagination-provoking. The idea of so
many gnarly, old vines pouring over volcanic cliffs was almost fantastical. I
was not surprised to see images of the cordon trenzados on many a label of the
local wines we perused from the region.
The more I reflected about the cordon
trenzado and how different it was from the vineyard systems I had seen before,
I realized I knew basically nothing about vine training to begin with. Why are
these practices needed? Why are some styles used in some places instead of
others? To help grapes grow, I figured, but I was curious to look further under
the hood to gain a better understanding of this key aspect of the viticultural
process.
So I did some research, and here's
what I learned:
Vine Training 101
Why do we need vine training? Grapes
naturally grow upwards towards the sun, climbing up other plants, trees, or
physical structures. Vine training is a way for humans to control otherwise
far-reaching vines, enabling us to optimize yield and making the grapes easier
to harvest.
A grapevine’s performance is maximized
by balancing the amount of fruit development with the amount of leaf
production. The leafy part of the canopy is the energy-producing part of the
vine. Too much fruit and too few leaves results in an imbalance, in which there
is not enough energy produced in the vines to fully ripen the grapes.
On the flip side, too many leaves is
not good either. Grape vines should be trained in a way that somewhat exposes
the grapes to sun and wind. Too many leaves can create excessive shading, which
inhibits grape ripening, and can trap excessive moisture, which can promote
grape diseases.
When deciding what vine training system
to use, growers will consider which systems can provide their desired yield
control, which is best for the local climate, humidity, and wind, and which can
suit any desired mechanization of tasks like pruning, irrigation, pesticide and
fertilizer application, and harvesting of the grapes.
The terms ‘trellising’, ‘pruning’ and
‘vine training’ are often used incorrectly and interchangeably. ‘Trellises’ are
the actual stakes, posts, wires, or other structures that the grapevine is
attached to. Most ‘vine training’ deals mainly with the ‘cordon’, the woody,
arm-like part of the vine, and the fruit-bearing ‘canes’ that extend from the
cordon. ‘Vine training’ systems are the combination of trellising and pruning
practices that are applied to the grapevine to influence the quality and yield
of that year’s crop. Cordons can be trained in unilateral or bilateral fashion
(one arm or two arms), and are usually trained horizontally along wire
trellises. In winter, pruning determines the number of buds that are allowed to
grow into grape clusters. The exact number of buds is regulated in some wine
regions. For example, in France, the number of buds is controlled by AOC
regulations.
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That’s far enough down the rabbit hole
of vine training research for today. I hope this is helpful to other classmates
that might be curious about the grape-growing process. I think it’s time to
plan a vineyard trip so we can see some vines through the lens of our newfound
viticultural knowledge!
Sources:
