Horticulture/Helleborus

Commonly known as Hellebores, the genus Helleborus is comprised of approximately 20 species (ongoing fieldwork may see this figure change) of herbaceous perennial flowering plants in the family Ranunculaceae. The genus is native to much of Europe, from western Great Britain, Spain and Portugal, eastward across the Mediterranean region and central Europe into Romania and Ukraine, and along the north coast of Turkey into the Caucasus. The greatest concentration of species occurs in the Balkans. One atypical species (H. thibetanus) comes from western China; another atypical species (H. vesicarius) inhabits a small area on the border between Turkey and Syria.

Hellebores are toxic if ingested, causing tinnitus, vertigo, stupor, thirst, a feeling of suffocation, swelling of the tongue and throat, emesis and catharsis, bradycardia (slowing of the pulse), and finally collapse and death from cardiac arrest.

Description
The flowers have five "petals" (actually sepals or tepals) 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).

Growing conditions
Hellebores grow best in shady locations with rich, well-drained soils. They do well in dry shade during the summer months.

Caulescent species
These four species have leaves on their flowering stems (in ../H. vesicarius/ the stems die back each year; it also has basal leaves).
 * ../Helleborus argutifolius/ – Corsican hellebore
 * ../Helleborus foetidus/ – Stinking hellebore or Setterwort
 * ../Helleborus lividus/
 * ../Helleborus vesicarius/

Acaulescent (stemless) species
These species have basal leaves. They have no true leaves on their flower stalks (although there are leafy bracts where the flower stalks branch).
 * ../Helleborus atrorubens/
 * ../Helleborus croaticus/
 * ../Helleborus cyclophyllus/
 * ../Helleborus dumetorum/
 * ../Helleborus abruzzicus/
 * ../Helleborus liguricus/
 * ../Helleborus bocconei/
 * ../Helleborus multifidus/
 * ../Helleborus niger/ – Christmas rose or Black hellebore
 * ../Helleborus odorus/
 * ../Helleborus orientalis/ – Lenten rose, Lenten hellebore, oriental hellebore (N.B. most of the Lenten hellebores in gardens are now considered to be H. × hybridus)
 * ../Helleborus purpurascens/
 * ../Helleborus thibetanus/ (syn. H. chinensis)
 * ../Helleborus torquatus/
 * ../Helleborus viridis/ - Green hellebore or Bear's-foot
 * ../Helleborus occidentalis/ (formerly H. viridis subsp. occidentalis)

Other species names (now considered invalid) may be encountered in older literature, including H. hyemalis, H. polychromus, H. ranunculinus, H. trifolius.

Hellebore hybrids
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.

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 pollination, leaving an apparently single flower, whereas doubles and semi-doubles tend to retain their extra petals after pollination.

Interspecific hybrids
Gardeners and nurserymen have also created hybrids between less closely-related species. The earliest was probably H. × nigercors, a cross between H. niger and H. argutifolius (formerly H. lividus subsp. corsicus or H. corsicus, hence the name) first made in 1931. H. × sternii, a cross between H. argutifolius and H. lividus, first exhibited in 1947, is named after the celebrated British plantsman Sir Frederick Stern. H. × ballardiae (H. niger crossed with H. lividus) and H. × ericsmithii (H. niger crossed with H. × sternii) similarly commemorate the noted British nursery owners Helen Ballard and Eric Smith. In recent years, Ashwood Nurseries (of Kingswinford in the English Midlands), already well-known for its Ashwood Garden Hybrids (H. × hybridus singles, semi-doubles, doubles and anemone-centres), has created interesting hybrids between H. niger and H. thibetanus (called H. 'Pink Ice'), and between H. niger and H. vesicarius (called H. 'Briar Rose'). The gardenworthiness of these hybrids has still to be proven.

Uses
Hellebores are widely grown in gardens for decorative purposes, as well as for their purported medicinal abilities and uses in witchcraft. They are particularly valued by gardeners for their winter and early spring flowering period; the plants are surprisingly frost-resistant and many are evergreen. Many species of hellebore have green or greenish-purple flowers and are of limited garden value, although Corsican hellebore (H. argutifolius), a robust plant with pale green, cup-shaped flowers and attractive leathery foliage, is widely grown. So is stinking hellebore or setterwort (H. foetidus), which has drooping clusters of small, pale green, bell-shaped flowers, often edged with maroon, which contrast delightfully with its dark evergreen foliage. H. foetidus 'Wester Flisk', with red-flushed flowers and flower stalks, is becoming popular, as are more recent selections with golden-yellow foliage.

The Christmas rose (H. niger) is a traditional cottage garden favourite, bearing 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.

Maintenance
Hellebores are easy to take care of, with the only maintenance required in early spring or summer, depending on the gardener’s preference.

In early spring, hellebores put up both their flowering stalks and their foliage. The previous year’s foliage tends to be rather unattractive by springtime, and can be removed (using pruners or scissors) without causing harm to the plant. Removing the previous year’s foliage will also help show off the flowers.

Hellebores are dormant during the summer months, and should be left alone. If the previous year’s foliage was not removed in the spring, it can be removed at any time. However, it is important to keep in mind that hellebores only put out new leaves in the spring, so severe cutbacks during the summer may cause harm to the plant.

Hellebores should not be cut back in the fall, as they continue to draw energy from their leaves over the winter. If the plant is covered by fallen tree leaves, these should be removed.

Propagation
Easily divides, but more commonly allowed to go to seed (most species self-sow freely). Propagated through tissue culture in commercial production.

Harvesting
For floral displays, the flowers can be cut individually, and allowed to float in a bowl of water. As they are frost hardy, the bowl can be kept outdoors as well as indoors, so long as the bowl will not crack in a hard freeze.

Pests and diseases

 * Black Spot caused by Coniothyrium hellebori
 * Blight caused by Botrytis cinerarea and Gloeosporium sp.
 * Crown Rot caused by Sclerotium delphinii
 * Winter Burn caused by a combination of harsh winter winds and sun.