What is field horsetail (508)?

Field horsetail (Equisetum arvense), also known as pewterwort, bears the number 508 but has a special status: it is not one of the six compost preparations (502–507) and, strictly speaking, is not a preparation but a plant care agent. Sprayed onto soil and plants as a tea or decoction, it serves to regulate fungal pressure.

Unlike the preparation plants, horsetail is not a flowering plant but a spore-bearing plant — related to ferns and mosses, a "living fossil" from the time when its relatives grew as tall as trees.

Making the preparation

The whole green above-ground plant is gathered on a sunny day, ideally shortly before St John’s Day, and dried in airy shade. It must be distinguished from the unsuitable marsh horsetail and wood horsetail: in field horsetail, the distances between the nodes of the stem are shorter than those of the side shoots.

Application and effect

For application, 200 to 300 grams of dried herb (or 1 to 1.5 kilograms of fresh herb) are simmered gently in 10 to 20 litres of water for about an hour. A five to ten per cent dilution of this is sprayed onto soil and plants in autumn, spring and high summer at a rate of around 100 litres per hectare — preventively and repeatedly.

In biodynamic understanding, it is the high silica content of horsetail, through its light forces, that is credited with containing excessive fungal growth.

Frequently asked questions about field horsetail

Is field horsetail (508) a compost preparation?

No. It has a special status — a plant care agent against fungal pressure, not a compost preparation and not a classic preparation.

How is field horsetail applied?

Sprayed onto soil and plants as a tea or decoction (boiled, then diluted) — preventively, repeatedly, in autumn, spring and high summer.

Quantity table:

Garden: 15g
Small farm: 125g
Farm: 1,25kg
Large farm: 7,5kg