Glossy purple blotches on peony leaves are a sign of leaf blotch, a fungal disease that looks worse than it is. Peony leaf blotch makes the foliage ugly but rarely harms the plant itself.
Leaf Spot: What You See
Look at the upper surface and then turn the leaf over; the colors are different.
- The upper surface of the leaf carries glossy, purplish-brown spots, and the underside of the same spots is chestnut brown.
- Spots start small, round and red or purplish on young leaves, just before the peony blooms.
- Each spot starts at 0.02 to 0.04 inch and reaches 0.08 to 0.12 inch across before penetrating the leaf.
- As spots spread later in the season, they run together into large, irregular, dark purple blotches.
- Infection tends to be heavier along the margins of the outer leaves.
- Leaves may twist or distort slightly as they keep growing.
Despite the look, the plant keeps its vigor, and the disease does not cause early leaf drop or stem dieback.
From the almanac
Peonies in your state
The dates on this page depend on where you live. Your state's page carries its frost dates, its USDA zones and the year laid out month by month.
Northeast
Southeast
- Alabama
- Arkansas
- Delaware
- Florida
- Georgia
- Kentucky
- Louisiana
- Maryland
- Mississippi
- North Carolina
- South Carolina
- Tennessee
- Virginia
- West Virginia
Midwest
Southwest
West
Pacific Northwest
Canada
Leaf Spot or Something Else?
Leaf problems can look similar, and the colors of the spots help sort them out. Check the color of the growth and which side of the leaf shows it before settling on a name.
Powdery mildew can look similar, and it has become more common over the years.
| Looks like | How to tell them apart |
|---|---|
| Powdery mildew: small white spots on leaves that can spread across the whole leaf | The coating is white to gray and powdery, and it sits over the leaf surface. Leaf blotch is glossy purple on top and chestnut brown underneath. |
| Leaf blotch: purplish-brown glossy spots | Spots begin small and round on young leaves, then merge into blotches, with a brown underside. |
In Illinois, both mildew and leaf blotch show up fairly regularly during the summer months. If a leaf has a dusty white film, think mildew. If it has glossy purple patches, think blotch.
What Causes Leaf Spot, and Where It Is Worst
A fungus causes it, now called Graphiopsis chlorocephala and formerly Cladosporium paeoniae. It grows on the surface of leaves, stems and petioles. The fungus survives on infected peony debris and probably on infected scales of the crown buds, which is why old foliage left in the bed matters so much.
Warm, humid weather gives the fungus ideal conditions to infect. In California, the disease is favored by rainy weather in spring.
Some peonies are hit harder than others. Susceptibility is quite variable, and many older cultivars are the most susceptible. The disease is also called red spot, measles or stem spot.
How to Treat Leaf Spot
Treatment is mostly cleanup, since the fungus lives in leftover debris and the plant itself is not in danger.
- Confirm the diagnosis by turning a leaf over, so that you match the glossy purple top to a chestnut brown underside before acting.
- Remove badly spotted leaves once the plant is done blooming, so that the fungus has less material to spread from.
- Discard those leaves in the trash rather than composting them, because the fungus survives on infected debris.
- In Arkansas, cut all spent top growth to ground level in fall and carry it out of the garden.
- Keep sanitation steady through the season, so that spores do not build up in the bed.
Cleanup removes infected debris that can carry the fungus.
How to Prevent Leaf Spot Coming Back
Prevention follows the peony year, and nearly all of it is housekeeping.
- Pick up any old peony leaves left on the ground, since the fungus survives on infected debris.
- Just before bloom, watch young leaves for small red or purple circles, which is when the first spots appear.
- After blooming ends, remove and discard spotted leaves so the infection does not carry forward.
- During rainy spring weather in California, look over the plants more often because those conditions favor the disease.
- In Arkansas, cut all spent top growth to ground level in fall and remove it from the garden.
If you are adding new plants, remember that many older cultivars are the most susceptible, so cleanup matters even more with them.
Where This Comes From
Leaf blotch develops when the fungus survives in infected debris and reaches peony foliage.
Common Questions
Will Leaf Spot Kill a Peony?
No. It looks ugly, but it does not significantly damage the plant, and it does not cause early leaf drop or stem dieback.
Can You Compost Peony Leaves with Leaf Spot?
It is safer to discard them. Infected debris carries the fungus, so spotted leaves are better kept out of the compost.
Do All Peonies Get Leaf Spot Equally?
No. Susceptibility varies quite a bit, and many older cultivars are the most susceptible.