Hellebores are easy to grow providing a few simple guidelines are followed. They prefer a rich soil with plenty of available moisture during their flowering period, but they also require excellent drainage: they are after all ‘snow-melt’ plants and, if you can grow them on a slope, they will naturally be well drained. Most are found on slightly alkaline soils in their natural habitat, but it really doesn’t matter too much whether the soil is neutral or slightly acidic, so long as there are plenty of nutrients. Avoid poor dry soils, peaty soils or waterlogged conditions.
It’s important to give them a sheltered site away from cold winds. Hellebores will tolerate drier conditions in summer providing there is some shade but bear in mind that too much shade all year round can reduce the number of flowers. They are best grown amongst deciduous shrubs and trees which will give them plenty of light in winter and spring, but which will provide some welcome shade in the summer months.
When to plant
In theory any plant in a pot may be planted at any time of the year ground and weather conditions permitting. However, there is evidence to show planting Hellebores in cooler conditions makes for a better plant, avoid planting in hot summer conditions wherever possible. If ground conditions are unsuitable because of water-logging or being frozen plants should be kept out of doors if possible, in a sheltered position, only bringing indoors in adverse weather. From experience it has been shown planting in the autumn gives very good results, but few plants are available at that time. Planting in the spring before soil and air temperatures become too warm is good practice. Those will light or sandy soils can plant generally on more occasions than those with heavier or clay soils.
Where to plant
Hellebores can be divided into two groups the green foliaged acaulescent group and derived hybrids and the acaulescent group which includes H. lividus, H. argutifolius and H. foetidus. The former prefers summer shade and coolers conditions whereas the later are happier in more sun where there is better drainage and are happier on flat sites.
Hellebores are very tolerant and will grow in most soils from slightly acidic through to slightly alkaline, as long as the ground is not extremely dry or waterlogged. They will tolerate drier conditions in summer providing there is some shade but bear in mind that too much shade all year round can reduce the number of flowers. They are best grown amongst deciduous shrubs and trees which will give them plenty of light in Winter and Spring, but which will provide some welcome shade in the Summer months. With just a few exceptions, they are hardy in the UK, but prefer a sheltered site away from cold winds. By planting your hellebores on a sloping bed, you will naturally improve the drainage, air movement and make it much easier to look into the flowers.
Soil preparation and planting
Hellebores are deep rooted and, to flower at their best, they need plenty of nutrients. Dig your soil as deeply as possible and mix in plenty of humus, in the form of leaf mould, spent mushroom compost, garden compost or well-rotted manure. Avoid soil preparation when the ground is frozen or waterlogged, wait until conditions improve before planting out. When planting on sandy or well drained soils it is worth adding a layer of organic matter to the bottom of the trench to retain more moisture. For those with clay soils, rough digging in advance of planting and allowing the winter frosts to break down the soil will help improve both structure and drainage and adding organic matter throughout the spade depth to keep the soil open can be recommended. On the heavier soils extra grit or coarse sand may be added and high planting is advisable.
A selection of recommended products for planting and after-care
If your hellebore is dry, water well from below before planting. Dig your hole deeper and wider than the pot. Carefully remove the hellebore from its pot, sprinkle Rootgrow mycorrhizal fungi on to the root if desired, then plant it at the same depth as in the pot, firming the soil back around. There is no need to tease out the roots as this causes unnecessary damage to their fibrous root system. Water well after planting. If planting in groups, allow at least 24 inches (60cm) between plants.
Apply an annual mulch of humus in July/August (when next year’s flower buds are being formed) and again in late December. Be careful not to mulch into the crown of the plant as this can cause the buds to rot. John Massey feeds his plants in early spring, and again in August/September when the new flower buds are being initiated. Lime often frees up nutrients, so he tends to use spent mushroom compost which contains some lime. Take care not to mulch into the crown of the plant as it can cause the buds to rot. Seaweed fertiliser is a good alternative and I also work in fish, blood and bone. Remember to keep your newly-planted hellebores well-watered during their first year. Remove the old faded flower stems usually around March/April, unless you require seed, to encourage next year’s developing new growth. Spray occasionally with a fungicide and insecticide for greenfly control (if desired) and keep a look out for slugs and snails on flower buds, new foliage and flower stems, treat accordingly.
Removing old foliage
H. x hybridus Ashwood Garden Hybrids and deciduous species: remove all foliage to the base in late December/ January. This reduces the risk of infecting the new season’s growth with any overwintering pests and diseases.
Evergreen species and interspecies hybrids (including Rodney Davey Marbled Group, H. x ericsmithii, H. x sternii, H. argutifolius and H. foetidus): remove damaged or diseased foliage only as needed to tidy them up in late Autumn. In late Spring remove old flower stems and leaves back to the base to reveal new young growth at the base.
H. niger: after flowering, remove only the old flower stems, damaged or diseased foliage as needed to tidy them up.
Saving your own seed
Some see this as a cheap way of raising your own plants but you no control of natures variables such as visiting pollinating insects or self-fertilization, so I generally do not recommend saving your own seed. Many doubles are sterile, and species will show considerable variation. If you wish to grow Hellebores from seed, it should be sown fresh in late July in deep pots and left outside for the onset of autumn weather conditions to break dormancy. Prick out into deep plug trays and leave until July before moving to one litre pots for a further twelve months. They should then be repotted into three litre pots for the final nine months before they flower. A well-draining John Innes compost is suitable or Melcourt potting compost.
Removal of dead flower heads is also to be recommended. Where seed is allowed to germinate naturally in the garden, the increased vigour of new plants growing close proximity to established choice plants means they are often swamped out with the vigorous but normally poor form seedlings overtaking your valuable choice plant. Seedlings are best hoed off or pulled out at an early stage.
Growing hellebores in containers
Choose a large pot with a wide rim for growing hellebores in containers
Hellebores are naturally deep rooting plants and therefore select a container that has a good depth and with a wider top than base to ensure you can easily remove the plant when it requires re-potting. Choose a container that is a little bigger than the existing pot, so you do not over pot the plant and risk it become waterlogged in soggy unused compost.
Use a good quality compost, preferably loam- based, such as John Innes No 2 with extra grit for drainage. Stand the container on pot feet. They are hungry plants and will need regular watering and feeding, with a high potash fertiliser such as Chempak No 4, in summer. Position the container where you can enjoy it from the house during flowering, then move it in Summer to a semi-shaded position. Re-pot every couple of years with fresh compost or preferably plant out directly in the garden.
Moving or splitting established hellebores
If you wish to move your plant or it becomes too big, you can lift and divide it in September or early spring. This goes against what is often quoted in books but dividing after flowering in spring can put plants under severe stress as May and June can be hot dry months when the plant is trying to recover following division in May. The whole plant should be dug up very carefully. When splitting, the large root system is far easier to handle if all the soil is washed off before dividing the root ball up using a knife or small saw, separating out into single crowns. Re-plant the crowns in well-prepared soil and keep shaded and moist but be aware that the new divisions may take a few years to recover. Those Hellebores with stems (Caulescent types) dislike being moved or divided and this group includes Helleborus niger, H. lividus, H. argutifolius and H. foetidus
(C) January 2019 Howard Drury and others