Hellebores, also known as Lenten roses, are plants that flower from February through May and feature evergreen foliage. While considered a relatively trouble-free plant, the hellebore is susceptible to leaf spot, a fungal disease that can spread quickly and have a devastating impact on all the hellebores in your garden.
What is Hellebore Leaf Spot?
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Caused by the fungus Microsphaeropsis hellebore, hellebore leaf spot affects plants — particularly new growth —beginning in late winter, when they're just starting to flower. While all species of hellebore are susceptible to the disease, the amount of damage they incur from it tends to vary.
The fungus thrives in the wet conditions of winter and creates tiny spores on the leaves and stems of hellebores. Rain and wind spread the spores to neighboring hellebores in the garden. If left untreated, these spores will continue to flourish and damage any new tissue that the plants develop throughout the summer and into the fall. New growth will continue to be infected with the fungus until steps are taken to prevent it from contaminating plants in the next growing season.
Do You Have Hellebore Leaf Spot in Your Garden?
If you have hellebores in your garden, now is the time to inspect them for signs of this fungal infection. Inspect the foliage and stems for round brown or black spots or patches. You may also notice some yellowing leaves or damaged flowers on the plants. If left untreated, the disease can even damage the entire year’s growth of flowers! The spots may appear small at first, but they'll grow rapidly as the infection progresses. This will continue until the tissue dies and falls out of the leaf, leaving a small hole in its place. If it spreads beyond the leaves, leaf spot can also cause the stem to collapse. As a result, the entire plant continues to get weaker.
What Should You Do If You Spy a Spot?
If you’re seeing spots, it’s not the end of the world. By addressing the issue early on and remaining vigilant with the treatment, you'll be able to control the fungus and enjoy healthy, thriving hellebores.
Remove the Affected Leaves
Pull any leaves with spots on them and destroy them immediately. If the plants' leaves have already fallen, clear them from around the plant and destroy them all the same. This infected debris will continue to infect your plants if left near them.
Spray With a Fungicide
The bad news is that there currently isn’t a fungicide formulated to specifically control hellebore leaf spot. However, most fungicides are formulated to treat a variety of plant diseases, and many of them have been shown to help control leaf spot as well. Follow the directions on the label to ensure you apply your fungicide of choice correctly. If your hellebores are located near any plants you plan to eat, it's probably best to make sure the fungicide won't be tainting them.
How to Prevent Hellebore Leaf Spot
According to Benjamin Franklin, “an ounce of prevention is worth a pound of cure.” This is as true in the garden as it is anywhere else. If you want to prevent hellebore leaf spot from infecting your hellebores this year, it’s important to take steps to prevent the fungus from flourishing. Keep your hellebores from becoming the next victims of leaf spot by following these simple tips:
Remove Most of the Foliage on the Plant (and on Surrounding Plants) in the Autumn
The fungus that causes leaf spot thrives in warm, wet conditions. By pruning back the foliage in the autumn, you’ll reduce the chances of a lingering infection from the previous year carrying over into the new one.
Spray a Preventive Fungicidal Product
Use a product that contains the fungicides mancozeb or myclobutanil in December and January. When you spray the plants, focus on their bases.
Keep Removing Damaged Foliage
Often, the fungus will go for the flowering stems in the winter, which causes the flowers to rot before they can fully bloom. If you notice any rotted or damaged flowers, leaves, or stems, remove them immediately. Keep removing damaged foliage until the plant is healthy.
Clear Dead Foliage From Around the Base of the Plant
This is a good rule to live by to prevent any plant disease or pest infestation — not just hellebore leaf spot. Leaving foliage to rot beneath the plant is the most common way plant diseases continue to thrive, even after you've begun treating them. Once a week (but more often if your hellebores are currently infected with the disease), take the time to clear all the debris out from around your plants. This will not only give your garden a neat and tidy appearance, but it'll also keep diseases and pest infestations at bay.
Destroy Affected Foliage
Keep hellebore leaf spot from infecting all of your plants by destroying the foliage you remove from the ones that are already infected. As with other plants that have been infected with a disease, you'll want to avoid putting these leaves in your compost bin, especially if you plan to use that compost in your garden. Instead, burn them (if you can) or throw them in the trash.
If you used scissors or secateurs to remove the leaves, be sure to sterilize them after using them. This will prevent them from spreading infection later on.
Encourage Air Circulation
If your hellebores are looking a little crowded, you may want to prune the plants around them to allow more air to circulate in their area. Air circulation allows the leaves to dry, which can reduce their host plant's chances of contracting leaf spot.