Hellebores make a lovely addition to any garden. They are long-lived evergreen perennials, with blooms that last several months. These plants are low-maintenance, deer- and drought-resistant, and flower in a wide range of colors from winter to early spring.
I. Appearance and Characteristics
Commonly known as hellebores, the Eurasian genus Helleborus consists of approximately 20 species of herbaceous or evergreen perennial flowering plants in the family Ranunculaceae, within which it gave its name to the tribe of Helleboreae. Despite names such as “winter rose”, “Christmas rose” and “Lenten rose”, hellebores are not closely related to the rose family (Rosaceae). Many hellebore species are poisonous.
The genus was established by Carl Linnaeus in volume one of his Species Plantarum in 1753.
Various species of this genus originated in Europe and Asia. 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.
The flowers have five petal-like sepals surrounding a ring of small, cup-like nectaries which are actually 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 persistence of the sepals contributes to the development of the seeds.
All helleborus plants are toxic, and all parts of the helleborus plant are toxic. Hellebore poisoning is rare, but it does occur. Hellebore plants are usually left alone by animals such as deer and rabbits because the leaves of the plant produce poisonous alkaloids, making them distasteful to animals. The poisonous alkaloids have been known to sometimes bother gardeners with sensitive skin.
II. How to Grow and Care
Sunlight
Hellebores prefer partial to full shade during the summer months but require more sunlight in winter. An ideal planting location is underneath a deciduous tree where they are shaded by foliage in summer but are exposed to full sun after the tree drops its leaves in the fall.
Temperature and Humidity
Hellebores are very hardy plants. Some varieties are more winter-hardy than others so make sure to select a type that fits your growing zone.
Extremely high summer temperatures and hot, arid climates are not suitable for hellebores.
Watering
Although they like some moisture, hellebores should not be allowed to sit in wet soil for a prolonged time or they will rot. Once established, they can handle drier soil.
Soil
Hellebores grow best in soil that is well-draining and rich with organic matter. If your soil is acidic, consider adding lime, as hellebores prefer neutral or even alkaline conditions. Before amending soil, make sure to do a soil test to determine soil pH levels and nutrient availability.
Fertilizing
Add an organic-rich fertilizer—compost or well-decayed manure—to the soil when planting, then continue to apply a layer in spring and early fall. Additional fertilizer is rarely needed if the soil is rich enough.
Planting Instructions
Plant hellebores in a shady location with evenly moist, well-drained soil. The soil should be neutral to slightly alkaline.
Select an area where the hellebores are in full view during their long bloom time. As long as there is shade, plant them in the front of a border or along a walkway. Shady spots under evergreen trees are ideal. Keep in mind that under deciduous trees and shrubs, hellebores won’t be protected from the sun during the winter. Hellebores are especially attractive when planted in small groups or as a mass planting.
Hellebores can be planted either in the spring or fall. In the fall, plant them at least a month before the ground freezes so that their roots have time to settle.
Dig a hole at least twice the size of the plant’s root ball and place the plant in the hole. Backfill it with original soil and tamp it down. Water thoroughly and regularly for the first month, or until the plant shows new growth, which indicates that it is getting established.
Space plants at least 15 inches apart.
Pruning
When some or all of the evergreen foliage of hellebores tends to become unsightly in the early spring, remove it to make room for new growth. There is no need to remove the stems after flowering, they remain attractive even after the bloom. Remove them if they start to deteriorate.
Propagation
Hellebores can be propagated by division. The best time to divide is in late winter before they flower. It is easiest to dig the entire plant and shake or wash off the soil so you can see where the buds are on the crown. Make sure each division has at least 2 buds. (Helleborus foetidus and Helleborus argutifolius do not divide well and are best started from seed.)
Most varieties will reseed and form colonies of plants, but hybrids can produce seeds that don’t resemble the parent plant. Seeds can produce plants that resemble one of the parent species, not the hybrid. You can move the seedlings to another location in the garden once they are large enough to handle and have developed true leaves.
Growing from Seeds
Hellebore seeds don’t remain viable very long so always start with fresh seed. Fresh seeds can be planted in containers and left outdoors throughout the summer. Keep the soil moist and you should see germination in either the fall or the following spring.
If you collect seeds from the pods on growing plants, they should be planted right away— they will germinate with minimal effort. However, if they sit too long outside of the soil, they develop a hard coating and go dormant. It can take a year or more for them to complete this dormancy cycle.
Stored hellebore seeds need to be stratified before planting. They will do this naturally outdoors, but if you want to start seeds indoors, it will take some finesse.
First, soak the seeds in hot water until they start to swell. This can take a day or two. Then, sow them in a pot filled with potting mix and keep the pots at about 70 degrees Fahrenheit for six weeks. Finally, move the pots to a cooler spot, around 50 degrees Fahrenheit. You should see germination and sprouting within another four to six weeks.
Potting and Repotting
Growing Hellebores in pots is not recommended for two reasons: in pots, the plant roots are not sufficiently insulated against heat in the summer and against cold in the winter.
Overwintering
Hellebores are winter-hardy and require little attention to make it through the harsh winter months. They will usually bounce right back at the first sign of spring.
Pests and Diseases
Common Pests
- Phytomyza hellebori
More commonly known as the Hellebore leaf miner, Phytomyza hellebori is a small fly that infests only the H. foetidus plants in the Hellebore family. The leaf miner fly digs tunnels into the leaves of the H. foetidus. The tunnels create brownish-black blotches on the plant. These later turn into a nesting ground where the flies lay their eggs. With time, the leaves turn a brownish-white along where the tunnels were dug. The larvae start to eat the inside of the leaves in August, and damage develops from the late summer to the early spring, with heavy attacks leaving the foliage disfigured by spring.
To control heavy infestations, the leaves can be removed and destroyed during the winter months before the adult flies emerge. Insecticides can be used with limited effectiveness in controlling larvae and fly populations in the plant. Insecticides may harm non-leaf miner flies if applied during the hellebore’s flowering period.
- Macrosiphum hellebori
Macrosiphum hellebori, commonly known as ‘Hellebore aphid’ or ‘greenfly’, is a sap-feeding aphid that infests the flowers and foliage of hellebore plants. The whitish-green aphids are about 2–4 millimetres (3⁄32–5⁄32 inch) long and form dense colonies on hellebores, coating them with a honeydew that can lead to the growth of sooty mold on the leaves and flowers of the hellebore. This species of aphid only affects hellebores and is most active in March and April when the hellebores are flowering and when few aphid predators are around, though they may infest during any time of the year.
Aphids start their feeding from the outside of the flowers, beginning at the leaves and then moving towards the flower petals of the hellebore. As the hellebore begins to open, the aphids try to move into the flower. The aphids then feed on the inner parts of the plant as well as the young stems and shoots. As the population grows, the aphids eventually eat the remaining parts of the plant, such as older leaves, for food.
Aphid infestations can be controlled through persistent squashing of the aphids manually or by using insecticides. It is not recommended to spray flowering hellebores as it may harm the non-aphid pollinating insects.
Common Diseases
- Botrytis cinerea
Botrytis cinerea or gray mold is a fungal disease that infects most ornamental plants. The fungus causes a decay of plant tissues and grows fuzzy gray-brown mold over the decaying areas, such as the buds, leaves, and flowers. Parts of the plant may shrivel and die after exposure to the mold, particularly the flowers. Typically the fungus infects plants only through an open wound or when the plant is under stress, but it has also been known to infect plants in humid conditions. If the humidity is low, the mold may be contained to discrete spots on the plant, but the mold has been known to spread rapidly in highly humid conditions. Gray mold is not seasonally dependent and can infect a plant at any time of the year. The fungus forms black seed-like structures in the dead plant tissue to create its spores to help it survive when new host plants are scarce. The spores are spread through the air to new plants.
To treat the infected plant, the first step is to remove infected and dying leaves, buds, and flowers immediately along with any other dead plant materials around the hellebore. The next step is to reduce the humidity around the plant by improving the ventilation and ensuring the plants are not overcrowded.
- Coniothyrium hellebori
Coniothyrium hellebori is a fungus that causes the most common fungal disease for helleborus species known as Hellebore black spot or leaf spot. The disease is most common not only in botanical and ornamental gardens but also in hellebore nurseries as well. Visible symptoms include blackish-brown spots that often appear as rings on the leaf blade or at the margins of the leaf. The spots continue to grow larger as the disease progresses, retaining an elliptical or circular shape and turning a dark brown or black color. The spots grow until they infect the whole leaf. Petioles and flowers can also be infected, but the disease is primarily seen in the leaves. The symptoms become visible in the spring and worsen with time.
The small black fruiting bodies which carry the spores, pycnidia, are formed in the dead cells of the leaf spots. The spores are mainly spread by water, wind, and wind-blown rain. The fungus has an ideal habitat to spread and grow at the final growth site for hellebore plants, and if left untreated, the spores remain for many years. The most effective method against C. hellebori is to remove and destroy the infected leaves immediately to avoid reinfection the following spring.
- Helleborus net necrosis virus
Helleborus net necrosis virus (HeNNV), also known as Hellebore black death, is an RNA virus that can cause serious disease in Hellebore plants by stunting or deforming the plant as it grows. The disease marks the leaves of the hellebores with black streaks, often following the veins of the leaf, and creating ring patterns. It can also mark the sepals and flowers with black spots or streaks but does not always do so. When symptoms are severe, new leaves have limited growth before dying off. The most seriously affected in the UK is H. orientalis, but all hellebores are susceptible to the disease. The most effective method of treatment against black death is to dig up and destroy all infected plants immediately. Many viruses are not transmitted through seeds, so it is possible to raise new disease resistant plants this way.
- Pseudomonas viridiflava
Pseudomonas viridiflava is a bacterium that has been claimed to cause disease in hellebores in New Zealand, among other plants. The bacterial disease manifested on hellebore plants in the form of black leaf spots, necrosis petal, and stem lesions. The most popular ornamental and commercial crop grown in New Zealand is H. orientalis and its hybrids, of which 90 percent of the H. orientalis in the Tauranga nursery contracted the disease after several days of moderate rainfall. The disease caused discoloration in the form of black leaf spots that were circular and about 1.5–2 mm in diameter, black stem lesions, and dry, grey to brown lesions with distinct margins on the flower petals.
The symptoms were different from other leaf-spotting hellebore diseases, such as those caused by the fungus Coniothyrium and the bacteria Xanthomonas The case in New Zealand is the only reported case of P. viridiflava infecting hellebores so far, but in other plants P. viridiflava has been reported to also induce symptoms such as leaf rot, leaf blotch, stem necrosis and blossom blight.
III. Types of Hellebore
- Christmas Rose
Helleborus niger offers pristine, pure white flowers from late winter to early spring on purple-spotted
1-foot-tall stems. Its fingered evergreen leaves are leathery in texture. Zone 3-8
- Hybrid Hellebores
Hellebores hybridize easily and numerous hellebore hybrids (Helleborus x hybridus) with superior qualities have been bred. They have nodding, bowl-shaped single or double flowers and come in a wide range of colors, from pure white to almost black, and some are speckled, spotted, and mottled on the inside. The flowers often turn green as they age. Popular varieties include ‘Anna’s Red’, ‘Wedding Party’, and ‘Honeymoon’. Zone 5-9
- Lenten Rose
Helleborus orientalis has large, cup-shaped, rose-like nodding flowers ranging from white to pink to rose-purple. The plant starts to bloom in late winter and for an extended time into the spring. It grows in clumps 1 to 1.5 feet tall and wide. Zone 4-9
IV. Uses and Benefits
In the early days of medicine, two kinds of hellebore were recognized: black hellebore, which included various species of Helleborus, and white hellebore, now known as Veratrum album, which belongs to a different plant family, the Melanthiaceae. Although the latter plant is highly toxic, containing veratrine and the teratogens cyclopamine (which can cause the fatal birth defect of cyclopia) and jervine, it is believed to be the “hellebore” used by Hippocrates as a purgative.
Despite its toxicity, “black hellebore” was used by the Greek and Romans to treat paralysis, gout and other diseases, more particularly insanity.
