Minerals

Minerals are the inorganic elements a plant draws up from the soil and concentrates in its tissues — calcium, magnesium, potassium, iron, zinc, silica and a long tail of trace elements. Unlike every other class on this site they are not carbon-based molecules built by the plant, but simple elements taken from the ground, which is why a plant's mineral profile mirrors the soil it grew in.

They are usually divided into the macrominerals, needed in larger amounts (calcium, magnesium, potassium, phosphorus), and the trace minerals, needed only in traces (zinc, iron, copper, selenium, manganese and others). Some herbs are notable accumulators — horsetail and nettle for silica, for instance — and this mineral richness underlies the traditional use of many leafy and root herbs as nourishing, remineralising tonics.

The medicinal pattern is one of dose-dependence. Minerals are essential nutrients and, at dietary levels from plants, generally safe and restorative; but they differ from most plant constituents in that many are outright toxic in excess, and for the trace elements the gap between enough and too much can be narrow. Plants can also concentrate unwanted heavy metals from contaminated soil, and a few mineral forms — such as the calcium oxalate crystals in some leaves — are locally irritant. As with vitamins, the hazard lies in concentration and imbalance rather than in the presence of the mineral itself.