Oak bark decoction | A plant-based spray used in organics and Biodynamics. The oak bark decoction is derived from the bark of the same strain(s) of oak gathered in the same way as for the biodynamic compost preparation 505. Oak bark decoction can be used to complement the common horsetail 508 decoction, reining in excess “moon forces” which make vines grow vigorously enough to attract fungal diseases like rot and mildew, especially around full moon. Oak bark has high levels of both calcium (c75% of the ash is CaO) on the one hand, and tannin on the other – the reason why ‘tanbark’ was widely used in tanneries (von Wistinghausen et al: 2000, p.50-51)

Tannic acid has insecticidal properties, while calcium protects against fungal growth. The oak bark decoction is seen by some wine-growers as creating grape with hardier, more ‘tannic’ grapeskins, tightening them to make them more resilient against fungal attack. Overuse of this decoction however may cause a severe blockage in plant growth (Pierre Masson (2014, p.129).

To make enough decoction for one hectare Masson (1998, p.27) advises placing 50 grammes of oak bark (which can be unground chunks) in 3.5 litres of cold water which is brought to the boil and left boiling for 15-20 minutes. Others macerate or simmer the oak bark in water for up to one hour. The concentrate is filtered off and then diluted in 35 litres of water.


Hugh Courtney., Applied Biodynamics 24/1998, p.5

Monty Waldin., Biodynamic Gardening (Dorling Kindersley, 2015).

Monty Waldin., Biodynamic Wine (Infinite Ideas, 2016).

Pierre Masson,. A Biodynamic Manual (2nd edition 2014, Floris), p.129.

Pierre Masson., Guide pratique de la bio-dynamie (France, 1998), p.27

Sattler, Friedrich., and Eckard von Wistinghausen, Bio-Dynamic Farming Practice (Bio-Dynamic Agricultural Association UK, 1992) trans. by A. Meuss, p.77.

von Wistinghausen, Christian., Scheibe, Wolfgang., von Wistinghausen, Eckard., and König, Uli., The biodynamic spray and compost preparations production methods Booklet 1 (Biodynamic Agricultural Association UK, 2000), p.50-51.