Why some grapes turn purple before others during Veraison

Walking through our vineyard this week, we were struck – and slightly puzzled – by the striking differences from one grape cluster to another. Some bunches are already deep purple, others are still almost entirely green. Even within a single row! So we asked ourselves: Why is veraison so uneven? And the answers are as fascinating as the transformation itself.

Here’s what we’ve learned.

What is veraison?

Veraison is the onset of grape ripening, when berries soften, sugar begins to accumulate, acidity drops, and in red varieties, anthocyanins (natural pigments) are produced, turning the grapes from green to red or purple.

But this doesn’t happen all at once. It’s a gradual physiological change that varies depending on many factors, both natural and human-influenced.

1. Grape variety (cépage)

Different grape varieties ripen at different speeds. In our vineyard, Merlot often starts veraison earlier than Cabernet Franc or the few rows of Pressac (Malbec). So part of the variation simply comes from which grape you’re looking at.

2. Vine age

Older vines tend to be more stable and balanced, with deep root systems that regulate water and nutrient uptake. This can lead to a more even onset of ripening. Younger vines, on the other hand, may respond more erratically to heat, rain, or drought, and show more variation in colour and timing.

3. Sun exposure and microclimate

Sunlight plays a major role. Grapes on the south-facing side of the row or exposed after early leaf thinning will ripen faster than shaded ones. Even a small hill, a tree, or a thick canopy can change a grape’s microclimate and delay colour change.

4. Vine vigour and water stress

Highly vigorous vines, often in richer soils or with high nitrogen, prioritise shoot and leaf growth. This delays grape ripening. On the flip side, moderate water stress tends to encourage earlier veraison as the vine shifts its energy to fruit maturity.

5. Soil differences and intra-parcel variation

Even within the same block, slight differences in soil type, moisture retention, drainage, or rootstock behaviour can lead to clusters ripening days (or even weeks) apart. Nature doesn’t follow perfect symmetry — and that’s part of what makes winemaking so nuanced.

What does it mean for the harvest?

For us, this uneven veraison is a sign that we’ll need to monitor each parcel, and even each vine — with care over the next few weeks. We’ll taste, measure, and observe, deciding when to harvest not just by the calendar, but by the balance of sugar, acidity, tannin and flavour.

It’s a reminder that great winemaking begins not in the cellar, but in the vineyard, and that nature always keeps us humble — and curious.

Come and see for yourself
If you're lucky enough to visit during this period, it's one of the most beautiful moments in the vineyard year. Colour, contrast, and complexity, just like in the glass.