Assemblage: and then there was light

Notes and anecdotes on the role of light in the crafting of our wines: in this edition of Assemblage, we focus our lens on chemical reactions and the luminous strategies of our winegrowers.

Life depends on light, and grapes are no exception. Across every stretch of sky, light imposes a universal set of laws. At Domaines Barons de Rothschild Lafite, light is a decisive factor—influencing the rhythm of photosynthesis, the growth and development of plants, the composition of the grape, and the strategies we employ to protect our vines.

We observe, experiment and test our conclusions across our vineyards to harness the benefits of light with precision and efficiency. And in this piece, we’d like to let you in on our best practices. 

In the beginning, there was photosynthesis

Photosynthesis is a vital process. It enables the plant to develop to maturity. By capturing solar energy, leaves transform water and carbon dioxide into sugars, enabling the grapes to swell and sweeten. Each vineyard must make the most of the light at its disposal. At Domaine de Long Dai, for instance, the varied topography creates light conditions marked by strong contrast. Some plots get more sunlight than others, influencing how quickly the grapes ripen. 

Photosynthesis affects every part of our process, down to the wine’s character itself. It influences the delicate balance between sugar, acids and the presence of aromatic compounds that give our wines their inimitable singularity. 

Scalding and sunscreen

For grapes, the sun can also be synonymous with danger. Scalding — or sunburns — can annihilate a generous year’s harvest. These burns can be caused due to excessive exposure, and they’re becoming a recurring problem in an increasingly unstable climate.

Since 2020, we’ve been searching for solutions to this scalding at our estates in Pauillac. Thanks to these tests, we can point (with relief) to shade nets that block a portion of the sun’s rays, or the use of kaolin clay that can act as an SPF barrier when applied to grapes. The goal remains to find a perfect equilibrium, allowing sufficient light for maturation, but not enough to destroy the harvest. 

Leaf removal: just enough exposure

Sometimes, it’s important to think ahead, and clearing some leaves from the vines can help achieve that. The art of leaf removal is an ancient technique that involves unveiling the vine to allow light to nurture the grapes without overwhelming them.

In our Pauillac estates, leaves are removed from the east-facing side of the vine, where the morning sun is gentle and nourishing. The leaves remain intact on the west-facing side, where the light can be harsh after midday. Depending on the location of the vineyard, all of this might change. Season after season, day after day, team members seek out a delicate foliar equilibrium, sparing the most protective leaves to adjust the plants’ exposure to sunlight. 

At Château L’Évangile, in August 2022, Technical Director Olivier Trégoat had a light bulb moment. After tasting one nearly-mature fruit, and in the interest of preserving each grape’s optimal aroma, Olivier decided to time the harvest according to each plant’s sun exposure. The difference between grapes harvested at sunrise and those picked at sunset was palpable—the nuanced effects of light could be tasted in the fruit. While this example isn’t strictly about leaf removal, it underscores the importance of balance and intuition. A bit like poetry, winemaking is an art of harmonising light and shadow.

The canopy and the parasol 

Canopy management is crucial for controlling light exposure. This roof of foliage, suspended above the grapes, must be adjusted according to the plant’s needs. If it’s too dense, it can trap humidity and increase the risk of mould. If it’s too sparse, it may overexpose the grapes to sunlight, leading to scalding. 

At Château L’Évangile, the height of the canopy has been modified in recent years to achieve a balance between phenolic maturity and sugar production. By reducing the leaf surface area, our teams seek to create finer wines while ensuring sufficient protection for the grapes. Each adjustment is made intentionally and according to the vintage in question, for each year comes with its own challenges. 

Photovoltaics: energy on demand 

What if light could do more than nourish vines? At Viña Los Vascos in Chile, the sun has become a source of power in its own right. Solar panels capture the abundant light and transform it into electricity, which in turn serves to keep the vineyard on the proverbial grid. Raquel Calatayud, Viña Los Vascos Director of Sustainable Development, Quality, and R&D, explains: ‘It’s a virtuous circle: what nourishes the vine also helps us irrigate and power our machines. The vineyard gives back to the grid the energy it doesn’t use.’

While solar panels are a common sight in Chile, European vineyards have yet to fully embrace this approach.

Light is omnipresent—illuminating our days while demanding our respect for its intensity. Winegrowers, too, are obliged to adapt, adjust, and innovate with this light. They trim, cover and harness light by working in harmony with it. But at the end of the day, the sun is the master of ceremonies, and wine an expression of this eternal struggle between light and shadow, nature and nurture.