Guide
Gravel or clay, and how the ground picks the grape
Warm stones for a late grape, cold clay for an early one. Then the blend does the rest.
The short answer
Gravel drains hard and holds the day’s heat, which suits Cabernet Sauvignon, a late grape with thick skins. Clay stays cold and wet, which suits Merlot, which flowers and ripens earlier. Cabernet brings structure, cassis and length; Merlot brings flesh, plum and an earlier peak.
What the ground does
Gravel is a heap of stones the rivers carried down from the Pyrenees and the Massif Central over 2 million years. Water goes straight through it, so the vine has to root deep and is never comfortable, which is what you want. The stones take the sun all day and give it back at night, so the fruit goes on ripening after dark. That is a bed built for Cabernet Sauvignon, which buds late, ripens last, and will make something hard and green if it does not get there.
Clay does the opposite. It holds water, warms slowly and stays cool in summer, which slows a vine down and feeds it in a drought. Merlot flowers early and ripens 2 weeks before Cabernet, so it can finish on cold ground where Cabernet would not.
Reading a real estate
Almost no estate is 1 soil, and the good ones say so plainly. On a Pomerol slope the top may be pure clay, the middle sandy clay and the foot gravel, and the estate plants each band to the grape that suits it. In the Médoc an estate may sit on 2 gravel rises over a clay subsoil, and the clay is the reason the vines survive a hot August. Beside Latour the ground is gravel over clay and limestone; a few hundred meters away it is deep gravel on a plateau, and the wine from each is a different animal.
What each grape brings to the blend
| Cabernet Sauvignon | Merlot | |
|---|---|---|
| In the vineyard | Buds and ripens late, thick skins, small berries | Buds and ripens early, thinner skins, bigger berries |
| In the glass | Cassis, cedar, graphite, firm tannin, length | Plum, fig, flesh, softer tannin, earlier appeal |
| Risk | Does not ripen in a cold year | Ripens too fast in a hot one, and can lose its acid |
| Job in the blend | The frame | The flesh that fills it |
Cabernet Franc is the third voice and the one that decides how good the wine is on the Right Bank: earlier than Cabernet Sauvignon, more aromatic, and capable of tasting green if it is planted on ground that does not suit it. Petit Verdot, Cot and Carmenère are seasoning, used in small percentages by estates that have somewhere to put them.
The one sentence to keep
The blend is not a recipe, it is a reading of the soil map. When an estate tells you it is 70% Cabernet Sauvignon, it is telling you what is under the vines.
Where to go next
Sources: FGVB, cahier des charges Pauillac · INAO, Pomerol