Arabidopsis petraea also known as Cardaminopsis petraea ; the Northern Rock-cress is very common all over Iceland. It grows on rocky grounds and soils of gravel and sand. Characteristic are the rather long flower stems with one or two entire leaves sprouting from a small basal rosette with incised and or toothed leaves. The flowering stems usually creep over the soil, especially in later stages of the development. It flowers early, i.e. from May to June. Under favourable conditions the plants grow vigourously. However they also grow on the desert highlands where they stay minute like many other hardy species. Some of the highland regions seem to be completely without vegetation but closer inspection learns that many minute specimen of species grow there. The Northern Rock-cress is regarded as one of the most common plants of Iceland.
It is a member of the cabbage (= mustard) family) (Brassicaceae formerly known as Cruciferae). The Icelandic name of this species is Melablóm.