Equisetum is the ninth of the biodynamic preparations indicated by Rudolf Steiner in his lectures. Its purpose is to regulate the watery element brought on by too strong or too weak moon forces. In other words use of equisetum is able to curb the strong moon forces (too much water) and encourage those forces when they are too weak (not enough water).
In the American biodynamic experience using Equisetum actually attracts or encourages rain provided that it is used in a water constellation (Cancer, Scorpio or Pisces) or curbs the conditions of excess water when used in the fire constellations (Aries, Leo or Sagittarius). This has the effect of encouraging the growth of beneficial fungi in the soil in the fermented form and minimising the occurrence of detrimental fungal diseases on plants when sprayed on them as a fresh concoction.
This preparation needs to be used with all of the other 8 preparations as a totality in order to achieve a harmony and balance of forces on the farm or garden.
In Australia where Equisetum Arvense has been declared a noxious weed Biodynamic Agriculture Australia has been able to import dried equisetum from New Zealand for sale. We sell this dried form with instructions for making your own equisetum preparation. 100gm dried equisetum is sufficient to make up fresh equisetum for the plants and atmosphere or fermented equisetum for the soil for 10 hectares.
We also sell 5ml vials of 8x potentised form of fresh and fermented equisetum.
In Australia we are able to substitute the needles of the male casuarina (She-oak) tree for the equisetum.