How to grow Hellebores
Hellebores are not difficult to grow in the cooler temperate areas of Australia. This would include most of Victoria, Tasmania, cooler mountainous regions of NSW and the cooler parts of South Australia. With their winter flowering and fascinating range of flower and foliage forms, Hellebores are deservedly popular. Here are a few thoughts on getting the best out of Hellebores in your garden.
The exceptions to the generally continental habitat of most Hellebores are the two closely related species H. argutifolius and H. lividus which are native to the Mediterranean islands of Corsica and Majorca respectively. Finally, there is the rare Chinese species H. thibetanus, isolated from nearest neighbour H. orientalis by over 5,000km.
The climatic conditions in which the different species are found in the wild are reasonably diverse. They range from semi-alpine to quite hot and dry low altitude areas. However they are mostly plants of semi shaded conditions, such as the edges of deciduous woodland, dryer in summer and damp in the cooler months. Hellebores are more tolerant of exposed sunny positions in cooler, high altitude regions.
Where to grow Hellebores
While Hellebores are shade tolerant plants, this has sometimes led to them being relegated to the deepest, darkest shade in many gardens. This is a pity because Hellebores will do much better given more light. They key is to provide some shade from the hot summer sun, but to allow plenty of light from autumn to spring. Plants will grow and flower more prolifically under such conditions. A position in the shade of deciduous, rather than evergreen, trees will often provide these conditions.
Probably the key cultural requirement for all Hellebores is good drainage. They are not tolerant of soggy wet conditions for extended periods. Areas with clay soils should therefore have organic matter added. If possible use raised beds with good soil depth. The caulescent species and hybrids (those with tall stems) such as H. argutifolius, H. foetidus and H. x sternii (a hybrid between H. argutifolius and H. lividus) strongly prefer a well drained spot.
Provided the drainage is good, Hellebores are not very fussy about soil type. While in the wild some species seem to be found in areas of limestone, in garden conditions the pH of the soil does not seem to be critical. That said, all Hellebores will grow better if some effort is made to improve the soil structure through cultivation and addition of organic matter.
Once established, Hellebores are reasonably drought tolerant. The acaulescent species and hybrids (clumping forms with separate flower stalks and leaves) such as H. x hybridus, have long thick roots extending from an underground rhizome and tolerate periods of dryness in summer. But adequate moisture levels during summer will make for better plants.
With the exception of H. lividis and some forms of H. x sternii, hellebores are all very tolerant of extremes of cold and frosts.
Growth cycle of Hellebores
The main period of growth for hellebores is from late autumn to early spring, when they put on strong new root growth, produce new leaves and flower. Hellebores generally go through a dormant period between summer and autumn. The nature and timing of this dormant period varies between the species. H. x hybridus remain evergreen but do not put on any growth over summer. The best time to plant and divide hellebores is from about May to September, giving them some time to establish before their dormant period.
Hellebores are not like some perennials which need regular dividing to perform at their best. The acaulescent hybrids and species are long lived plants and will grow well in a spot to their liking for many years. However older clumps of H. x hybridus probably would benefit from dividing.
A little annual maintenance will keep your Hellebores looking at their best. Removal of the old foliage of the acaulescent types is best done in autumn or winter, as the new flower or leaf growth begins to emerge. By then the old foliage is looking a bit worse for wear anyway. This practice will also help show off the flowers to better effect.
In the caulescent types (H. foetidus, H. argutifolius, etc) old stems can be removed when flowering is finished, to encourage growth of new stems in spring.
As with other members of the Ranunculaceae family, Hellebores will take plenty of feed when they are in growth. In good garden soil with plenty of added organic matter, a lot of additional feeding may not be necessary. However growth rate and flowering will improve with some additional fertiliser.
The period from about April to August is when feeding is most beneficial. The type of fertiliser is not critical and can be either organic or inorganic as you prefer. Look for something which is both ‘complete’ and ‘balanced’. In pots a controlled release fertiliser is best.
Pests and diseases of Hellebores
If well grown Hellebores suffer from few serious pests and diseases.
Aphids can affect the new growth of established plants in autumn and seedlings in spring, depending on climate. These can be controlled with some judicious use of low toxic sprays such as insecticidal soap, garlic and pyrethrum products.
Environmental conditions can induce fungal diseases such as black spot or botrytis. Serious outbreaks are not common. Some plants seem to be more susceptible than others. Cultural practices, such as removing old foliage early in the annual growth cycle, are the easiest method of control.
Growing Hellebores in pots
Hellebores are not ideally suited to long term residence in pots. However they can be grown successfully in pots if a few principles are kept in mind. H. x hybridus have a large vigorous root system and will rapidly outgrow smaller pots.
Well grown one year old seedlings can fill a 150mm pot and two year old plants will probably find 200mm pots too small. For long term pot culture of these plants you will need to keep them in 300-400mm tubs and provide controlled release fertiliser each autumn.
I find the caulescent species such as H. argutifolius and H. foetidus less easy to grow in pots once they approach full size. The only hellebore from this group which seems to grow quite well in pots is H. lividus. This species can look stunning in a terracotta pot.
Growing Hellebores Fact Sheet
Article by Peter Leigh (Post Office Farm Nursery)
WEB SITE www.postofficefarnnursery.com.au