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.
Maintenance tasks
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.
Fertilising Hellebores
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 org
anic 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.
Peter Leigh
Post Office Farm Nursery
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