Viola lutea subsp. calaminaria

The plant occurs from Kelmis (La Calamine in French) in the Belgian province of Liège across the borders to Germany and the Netherlands.

The plant has adapted to an excess of zinc in the tailings of a former mine, the heaps of stone left over after separating the valuable fraction from the ore. By evolving the ability to cope with the toxic heavy metal pollution, this violet has gained an advantage over the other plants in the ecosystem, as is able to become the locally dominant floral component of such habitats.

[2] Mining for zinc began in earnest regionally in the Roman era, and this violet would most likely have mutated to take advantage of the heavy metal pollution at some time afterwards.

This can be seen in its incomplete adaptation to the toxic effects of zinc: the viability, sporogenesis and pollen morphology of such violets are often defective.

[2] The plant grows to a height of 10 to exceptionally 40 cm, forms rhizomes, and flowers from April to July.

The main threat to the species is not enough grazing by livestock -as herding has become less attractive as a career, trees would naturally start to grow in these areas if modern mechanical measures were not taken to maintain the habitat.

An important part of the habitat is people with lawnmowers, this stops native trees from naturally growing here. In the past livestock would have performed this function. People conserving violets at NSG Wäschebach, Tieberg