Name: Symphytum officinale L.
Croatian name: Gavez, Crni korijen
English name: Comfrey
This is the perennial plant with a black, turnip-like root and hairy, rough and prickly stems and leaves. The plant grows quickly and can be up to 1 m tall. The flowers are tubular (five grown-together petals), blue-violet in colour, forming a curl (cincinnus) on the end of the flower stalks.
It likes dump, fertile soil.
It is well known herb and medicinal plant, though it's use is suspicious and should be used with care.
Image credit: metafro.be