Lithotham is a sea algae (Lithotamnium calcareum) found growing in the waters off the Brittany coast, France. It is rich in both calcium and magnesium and other mineral elements essential for vine growth. It became popular as a soil amendment among those winegrowers following the precepts of the Lemaire-Boucher method in France in the 1960s and early 1970s. Lithotham can also be used in powdered form to dry grapes and prevent grey rot. Its use is permitted in organics and biodynamics. See also Seaweed liquid fertiliser. See also seaweed liquid sprays.