Pest and diseases
Hellebore plants are very pest and disease tolerant. However, the right choice of location is a key factor in encouraging vigorous and healthy plant growth and keeping the plants free of pests. One of the reasons the varieties in the Helleborus Gold Collection® are virtually unsusceptible to pests and diseases is our breeders' extensive work over recent years.
The following is a list describing the pests and diseases that can occur in hellebores.
Aphids, extremely seldom also leaf miners, can occur on young plants or fresh leaves. There are biological treatments available at garden retailers that can be used to control these unwanted guests; biological agents can also be used to combat slugs and snails in moist summers.
The popular “slug pub” can also be used to control slugs and snails. Aphids can be controlled by spraying the plants with a home-made stinging nettle slurry. (Marie Luise Kreuter's herb garden)
In a hard winter, mice sometimes strip the buds. There is very little you can do about mice in the garden, other than perhaps keeping a cat.
If the plants are dwarfed for no apparent reason and not even the best plant care is helping, they could be infested with root nematodes. Nematodes are tiny roundworms invisible to the naked eye. They tap the roots and interfere with the plant's water and nutrient uptake. Control is extremely difficult. The only realistic solution is to dispose of any plants that show symptoms in a waste bin to prevent the nematodes from spreading.
Also, thrips can populate the plants in autumn. Normally, nothing needs to be done against them, because they will disappear in the first frost as fast as they appeared. Caterpillar damage can occur on flowers and stems in summer. However, it only occurs occasionally and does not normally require any action.
Diseases caused by fungi are very disagreeable, and in addition to impacting appearance, they can potentially actually kill the plants.
Blackspot, Coniothyrium helleborie, is the most widely occurring fungus that affects hellebores. As the name indicates, black spots, often spreading from the leaf edges, appear on the parts of the plants that are affected by the disease. Since the fungus can infest any part of the hellebore plant, you should carry out a thorough disease control programme as soon as the first signs begin to show. First of all, remove all affected plant material and dispose of it in a waste bin to prevent the fungus from spreading.
After removing the affected areas, keep a watchful eye on the plants over the following weeks. Excessively low pH levels or too much moisture will encourage fungal diseases. If this is the case, transplanting affected hellebores to a more suitable location will generally help improve plant health.
Blackspot should not be confused with Black Death. Black Death is a viral disease causing zig-zag streaks to form on the infested leaves. These streaks can also appear on the blooms. Since viruses cannot be controlled, destroy any affected plants immediately. As a preventative measure, it is recommended that you take direct steps to combat aphids, as these are considered to be major virus carriers.
In spring, apparently healthy leaf stems can be infested with rhizome and stem rot. It causes shoots to fall over at the base for no apparent reason. The shoots have in this case basal brownish or blackish rotten spots. The problem can be caused by a variety of fungi, such as Pythium, Phytophthora or Rhizoctonia. Since control of these pathogens is difficult, be sure to provide the plants with good drainage as waterlogging tends to encourage the occurrence of these fungi.