Gentiana lutea or great yellow gentian produces large elliptical leaves and spikes of yellow flowers to 3 feet or more in summer. It is a European mountain meadow native. The bitter root has long been used in herbal medicine for a variety of ailments and is the main ingredient in Angostura bitters. Grow in sun to part sun in moist, well-drained, moderately fertile soil. Tolerates a wide range of soils as long as they have good drainage. Hardy to -40 degrees. F.