A larger Trillium being a little more amenable to conditions, the vigour probably helping here. Leaves are a deep green with visible veining, reaching almost 20 cms wide and long each. Rigid scapes carry the whole flowering stem to a height of almost 60 cms in larger colonies. Flowers are deep red, the petals reflexed backwards, sepals are sulcate hence the latin name. The flower of this species is held on an erect pedicel lifting the flower clearly visible.