Herb Robert (Geranium robertianum) prefers to grow on rock walls and quarries, as long as the rock consist of something richer in nutrients than granite, such as mica gneiss and amphibolite. In Mustavuori, the excavation of fortifications has also released additional nutrients into the environment for plants to use. In addition, Herb Robert makes use of the lime mortar used in the fortifications on Vallisaari island, for example.
Herb Robert leaves are covered in glandular hairs that emit an unpleasant smell when touched. In the past, herb Robert was used medicinally to treat haemorrhages and wounds, and as an insect repellent.