Commonly known as Hellebores, members of the genus Helleborus comprise approximately 20 species (ongoing fieldwork may see this figure change) of herbaceous perennial flowering plants in the family Ranunculaceae, within which it gave its name to the tribe of Helleboreae. Many species are poisonous.
The flowers have five "petals" (actually sepals) surrounding a ring of small, cup-like nectaries (petals modified to hold nectar). The sepals do not fall as petals would, but remain on the plant, sometimes for many months. Recent research in Spain suggests that the persistent calyx contributes to the development of the seeds (Herrera 2005).
Although the flowers of some species may resemble wild roses (and despite some of their common names, such as "Christmas rose" and "Lenten rose"), hellebores do not belong to the rose family (Rosaceae).
Other species names (now considered invalid) may be encountered in older literature, including H. hyemalis, H. polychromus, H. ranunculinus, H. trifolius.
The so-called Christmas rose (H. niger), a traditional cottage garden favourite, bears its pure white flowers (which often age to pink) in the depths of winter; large-flowered cultivars are available, as are pink-flowered and double-flowered selections.
The most popular hellebores for garden use, however, are undoubtedly H. orientalis and its colourful hybrids (H. × hybridus). They flower in early spring, around the period of Lent, and are often known as Lenten hellebores, oriental hellebores, or Lenten roses. They are excellent for bringing early colour to shady herbaceous borders and areas between deciduous shrubs and under trees.
Hybridising (deliberate and accidental) between H. orientalis and several other closely-related species and subspecies has vastly improved the colour-range of the flowers, which now extends from slate grey, near-black, deep purple and plum, through rich red and pinks to yellow, white and green. The outer surface of the sepals is often green-tinged, and as the flower ages it usually becomes greener inside and out; individual flowers often remain on the plant for a month or more. The inner surface of each sepal may be marked with veins, or dotted or blotched with pink, red or purple. "Picotee" flowers, whose pale-coloured sepals have narrow margins of a darker colour, are much sought-after, as are those with dark nectaries which contrast with the outer sepals.
Recent breeding programmes have also created double-flowered and anemone-centred plants. Ironically, doing this is actually reversing the evolutionary process in which hellebores' true petals had been modified into nectaries; it is usually these nectaries which become the extra petals in double, semi-double and anemone-centred flowers. Double hellebores provide a very intesting varaition to the standard hellebore. They are generally easy to maintain and share the same planting conditions as the standard hellebore.
Semi-double flowers have one or two extra rows of petals; doubles have more. Their inner petals are generally very like the outer ones in colour and patterning. They are often of a similar length and shape, though they may be slightly shorter and narrower, and some are attractively waved or ruffled. By contrast, anemone-centred flowers have, cupped within the five normal outer petals, a ring of much shorter, more curved extra petals (sometimes trumpet-shaped, intermediate in appearance between petals and nectaries), which may be a different colour from the outer petals. These short, extra petals (sometimes known as "petaloids") drop off after the flower has been pollinated, leaving an apparently single flower, whereas doubles and semi-doubles tend to retain their extra petals after pollination.
Several legends surround the hellebore; in witchcraft it is believed to have ties to summoning demons. Helleborus niger is commonly called the Christmas rose, due to an old legend that it sprouted in the snow from the tears of a young girl who had no gift to give the Christ child in Bethlehem. In Greek mythology, Melampus of Pylos used hellebore to save the daughters of the king of Argos from a madness, induced by Dionysus, that caused them to run naked through the city, crying, weeping, and screaming.
During the Siege of Kirrha in 585 BC, hellebore was reportedly used by the Greek besiegers to poison the city's water supply. The defenders were subsequently so weakened by diarrhea that they were unable to defend the city from assault.
Because of the similarity in appearance, the corn lily is sometimes mistaken for hellebore.