Hellebore Leaf Spot – How to Identify It Early and Stop It From Spreading

Hellebores are a joy in late-winter gardens, lighting up bare borders with their delicate beauty. They’re vulnerable to a fungal disease known as hellebore leaf spot at this time of the year, though, and swift action is essential to prevent its spread and save your blooms. But the good news is that this common hellebore disease is easy to identify and straightforward to deal with.

What Should I Look For?

Watch out for small, circular, black or brown spots on the leaves of your hellebores. If you take action at this stage of the fungus lifecycle, your precious plants will likely recover well. Over time, these spots enlarge and merge so, if your plant has been infected for some time, you’ll see dark patches covering portions of the leaves. This can easily be mistaken for foliage damaged by below-freezing temperatures. In severe cases, the spots spread to the stems, causing them to collapse, and infected leaves wither, yellow, and die.

How Do I Save My Hellebores?

As long as you act quickly, your hellebores should be just fine. Your first step is to remove all leaves and stems with black or brown spots. Be brutal – because this is a spreading fungal disease, it’s better to over-prune a plant than leave any infected material behind.

Some hellebore species, such as Helleborus niger, grow leaves and flowers on the same stems, so simply remove any infected leaves. Others, like Helleborus x hybridus, carry their flowers on separate stems to the leaves, so you can safely remove the entire foliage stem.

Hellebore sap is a skin irritant and is toxic if ingested, so always wear waterproof gloves such as these Cooljob Gloves from Amazon whenever cutting or handling these plants.

How Do I Stop the Disease Spreading?

The fungal spores of Microsphaeropsis hellebori can survive on the removed leaves and re-infect plants, so bag your prunings and dispose of them in your household waste. Whatever you do, don’t compost them! If you used hand pruners to remove the infected parts, disinfect them thoroughly – any household disinfectant will do the trick, or use a solution of one part bleach to nine parts water.

Can I Protect My Plants Long-Term?

The trick to preventing hellebore leaf spot is to understand that it’s a fungal disease. Fungal spores are highly resilient and can lie dormant for years until favorable conditions allow them to germinate. But don't worry: stopping them from infecting your plants is simple if you follow this fail-safe 5-step plan, and now's the perfect time to start.

1. Prune Harshly

Your first line of prevention should be good plant hygiene. Most hellebores are semi-evergreen, so regularly check the foliage year-round, and remove all dead or damaged leaves. Then, when flowerbuds first emerge in winter, prune your hellebores, snipping off last year’s leathery leaves to get rid of potentially infected foliage. This also encourages fresh growth of healthy new leaves, and helps to show the flowers off.
Be sure to bag up your prunings and dispose of them in your household waste, just in case.

2. Mulch Generously

Once you're done pruning, apply a thin layer of mulch, being careful to keep the organic matter away from the crowns. Hellebores are naturally woodland-edge plants, so use leaf mold or any wood-based mulch such as this Organic Aspen Mulch from Amazon. As well as providing your plants with nutrients, mulching will help keep the environment around your plants healthy. It will also stop rain-splash transferring spores in the soil onto lower leaves.

If any of your plants were infected last year, it’s good practice to scrape away the surface of the soil before mulching – a trowel with a serrated edge, such as a Sumio Weeding Trowel from Amazon, makes it easy.

3. Improve Airflow

Fungal diseases need damp conditions to flourish, so take steps to ensure good airflow around your hellebores. Most hellebores readily self-seed, which can lead to congestion or the seedlings smothering the mother plant. Pull out any unwanted plants – while mature hellebores hate to be moved, any seedlings can be rehomed to another spot in your border. In the future, if you don’t want your hellebores to self-seed, simply snip off faded flower stems before seedpods form.

4. Water Carefully

Once established, hellebores don't need watering in winter unless there's a prolonged dry spell. They don't like their roots to be waterlogged, and that mulch layer will retain soil moisture. Over-watering will weaken your plants and encourage the damp conditions that leaf spot loves. If you do need to irrigate, be sure to aim water at the soil rather than dousing the plant: a can with a long spout and down-angled rose, such as this 2-Gallon Can from Amazon, makes it simple.

5. Grow Considerately

Healthy plants are more resistant to disease, so make sure you’re giving your hellebores the conditions they need to thrive, especially if you're growing them in a container, when they’re more reliant on you to meet their needs.

What if My Plant Is Heavily Infected?

If Microsphaeropsis hellebori spores have taken a firm hold of your hellebores, use a copper-based fungicide such as Bonide Captain Jack’s Copper Fungicide from Amazon.

Be careful not to mistake hellebore black death, which is as deadly as it sounds, for a severe infection of Black Spot. Black death is a far more serious condition caused by the virus Helleborus net necrosis virus, but is easily recognized as plants become stunted and have black streaks or netting patterns on their leaves, rather than spots or patches.

Are Some Varieties More Resistant?

Many newer hellebore cultivars have been bred to be more resistant to disease, including leaf spot. The attractive FrostKiss hybrids have marbled foliage, which is often more resilient, and come in a range of fabulous tones.