Helleborus viridis – The Green Hellebore is considered to be the most beautiful of all the green-flowering species and generally blooms from February to April. They are long-lived and a good choice for cut flowers. It prefers a part to full shade exposure and is generally considered a slow-growing species. Divided green foliage. Grows 10-16″ high by 18″ wide. Hardy to zone 6.
Helleborus foetidus – This native of central and western Europe goes by the common name of Stinking Hellebore, but despite this is an RHS Award of Garden Merit winner. It is an evergreen species with large clusters of pendent green flowers (often purple rimmed) that start opening in late winter. Tolerates morning or late afternoon sun. Grows 18-24″ high by 18″ wide. Zone 6.
Helleborus purpurascens – The flowers of this herbaceous species are usually borne before the leaves emerge and are downward facing. They vary from purple to light pink and even slate grey, often with green in the center. It can bloom as early as mid December and tolerates part to full sun in its native Europe. Grows 4 to 12″ high by 12″ wide. Hardy to zone 5.
Helleborus odorus – An easy to grow Hellebore with late winter blooms (about 2″ across) that are yellowish-green, often with a distinct elderberry fragrance. It is an herbaceous species that is closely related to Helleborus cyclophyllus. Despite its easy disposition, it can be very difficult to find at your average garden center. Grows 12-20″ high and wide. Hardy to zone 5.
Helleborus multifidus – This native of the Adriatic coastal mountains and Italy has been divided into four subspecies, with subsp. hercegovinus being the most commonly available. This one has very finely cut, almost lacy foliage and 2″ wide cup-shaped green flowers that start blooming in late winter. Prefers alkaline soils. Grows 12″ high by 18″ wide. Hardy to zone 7.