Great Yellow Gentian – Gentiana Lutea July 4, 2014 1024 × 1024 Great Yellow Gentian – Gentiana Lutea Great Yellow Gentian – Gentiana Lutea The great yellow gentian is a medicinal plant. The roots were once harvested it the Autumn and used to treat stomach complaints. It’s roots are also the most bitter substance known to man and are used in angostura’s bitter.