Russian comfrey is a sturdy hybrid of common comfrey (S. officinale) with rough comfrey (S. asperum). Common comfrey is a traditional herbal medicine in Europe, whereas rough comfrey is native to the Caucasus. The two met in Sweden in the mid-1800s, and the first description of their hybrid offspring dates from about that period, in central Sweden. Since then Russian comfrey (whose common name in Finnish is Swedish comfrey) has been planted in gardens. About the middle of summer the small, funnel-shaped and variable blue-red flowers appear.
Of the three comfrey species mentioned above, Russian comfrey is the most commonly grown in Finland, often found on the sites of old houses. At Mustila it has spread around the ruins at Ketunmäki (Fox Hill) and the buildings on Nikkarinmäki (Nikkari Hill), which include the Arboretum office. Russian comfrey spreads strongly from its roots. It produces masses of foliage which produce a good fertiliser when steeped in water. The comfreys were also considered as possible cattle fodder, but they failed the taste-test.