🌿 Bordeaux mixture

Bordeaux mixture is a bluish blend of copper sulphate and slaked lime. It is sprayed on leaves to protect plants from fungal diseases. In vineyards it is used against downy mildew.

It was devised in France, in the Bordeaux area, in the late 19th century. At that time downy mildew, which had come from America, was badly harming vines. Growers noticed that roadside vines sprayed with the mixture to put off thieves stayed healthy. That is how the protection arose, and it is still used today.

Copper does not break down in soil, so its use is limited by rules. It is allowed in organic viticulture, but only in small amounts. Bordeaux mixture is linked to downy mildew, which it is used against, and to organic viticulture. The name does not mean wine from Bordeaux; it only marks where the mixture was devised. The blue colour of the mixture shows clearly on leaves, so traces of treatment are visible on the vine.