Dog’s mercury (Mercurialis perennis), which is typically found in the oak zone, requires a growth site particularly rich in nutrients and calcium in order to thrive. In Helsinki, dog’s mercury is only found in a few areas, namely in the riverside herb-rich forests of Mustavuori and Haltiala, from Pitkäkoski to Ruutinkoski.
It is easy to find in the spring if you know what you’re looking for, though the plant is not particularly eye-catching dues to its modest flowers. Dog’s mercury is poisonous. It is known as a traditional medicinal plant. Nowadays it is used in natural cosmetics.