Weed manures | Weeds out-compete cultivated crop plants and as a result contain vital nutrients often missing from soils–nettles and dandelions are high in calcium, iron, and magnesium, while thistles are high in phosphorus as well as trace elements like zinc and manganese. Balance can be restored by macerating weeds in water to make a concentrate, then spraying this on the soil. The extract can be made from the branches, leaves, flowers and roots of whichever weed predominates. Ferments made from weeds which spread through rhizomes and stolons are supposed to be especially beneficial (Pierre Masson: 2014, p.151). Weed manures should be made from just one weed type at a time, as mixing species may interfere with the breakdown process (Peter Proctor: 1997, p.68). See plant-based sprays.
Peter Proctor,. with Gillian Cole., Grasp the Nettle (Random House New Zealand, 1997), p.68
Pierre Masson,. A Biodynamic Manual (2nd edition 2014, Floris), p.151.