Yarrow cold extract | A plant-based spray used in organics and Biodynamics. Yarrow cold extract is derived from yarrow flowers. Yarrow flowers are also used to make the Yarrow 502 compost preparation, one of nine preparations used by Biodynamic growers. Its application is said to make fungicides more effective.
How made | Roughly chop 20 grams of dried flowers. Soak for 24 hours in cold water. Filter before using. Use 1 litre of extract in 10 litres of water. Yarrow cold extract can be combined with cold extracts of tansy and common horsetail.
Pierre Masson, Guide pratique de la Bio-Dynamie à l’usage des agriculteurs (France, 1998).