Peonies produce medium size bushy flowers and die back in the winter. There are two broad types of peonies herbaceous peonies and tree peonies. A range of factors can influence the appearance of the leaves of peonies so today I will discuss what these are.
Not enough sun and water, nutrient-poor soil, diseases, and pests cause peony leaves to turn brown. To treat it move your peonies where they will get 6 hours of sun per day, ensure the soil is rich, dark, and free-draining, and treat pests and diseases with neem oil.
Peonies naturally die back in winter, where the leaves will turn brown and fall off. With tree peonies, they will leave a stick in the ground, whereas, herbaceous peonies die back completely to ground level. In this article, I will explain the symptoms of peony leaves turning brown that aren’t related to them losing their leaves in winter naturally, as well as, a more in-depth explanation about how to solve each of these issues.
Peony leaves can turn brown due to a lack of water that makes its way to the roots. This can be caused by not watering your peonies enough, too many weeds around the base of the plant, or clayey soil that doesn’t allow water to flow through easily.
The signs of not enough water are the plant will begin to droop. When they are consistently not getting enough water the tips of the leaves will become brown, and the brown area will become dry and crumbly.
- Water them with 1 inch (2.5cm) of water around the base once per week.
- In very hot weather if you suspect the soil is drying out water them every 2 days or so.
- Put a layer of mulch around the base of the plant to keep the moisture in the soil.
Not enough sunlight
The two types of peonies need different amounts of sun. Tree peonies that retain stalks need full sun or semi-shade throughout the day. But need to be kept out of the morning sun. Tree peonies need a minimum of 6 hours of sun a day. The sunlight gives the plant energy and also dries the leaves which reduces the risk of diseases that can turn the leaves brown.
Although, the amount of sunlight won’t cause the leaves to turn brown directly. If kept in full shade peonies can begin to die, especially herbaceous peonies. And as they die the leaves will first turn brown, before falling off.
- Replant herbaceous peonies where they will get 6 hours of full sun per day.
- Replant tree peonies in semi-shade to full sun but not where they will get morning sun.
Diseases such as leaf blotch and blackspot
Various diseases can occur on only one peony plant but can spread to any others that are close by. Leaf blotch is very common, but others such as powdery mildew, black spot, and fusarium can also occur according to the American Peony Society. Leaf blotch starts off as brown spots on the leaves, and when left untreated begins to expand and spread onto other leaves.
Blackspot appears as dark brown/black spots on the leaves that are surrounded by a lighter colored brown area. Powdery mildew and other types of mold arrive via mold spores that sit on the leaves and grow sucking out all the nutrients and turning the leaves brown. Increasing airflow dries out the mold and diseases helping to stop them from spreading. Fusarium is a soil-born fungus that can lay dormant for a long time. But, it’s very difficult to know if this is what’s causing it because the only symptom is brown and wilting leaves.
- Spray the plant with a neem oil and water mix.
- When watering don’t get water the leaves as it can help the disease to spread.
- Trim away affected areas where possible, and discard them where the disease won’t spread to other plants.
- Increase airflow by removing weeds and pruning adjacent plants.
- If it persists replant them into fresh soil that won’t have fusarium.
Poorly draining soil
According to Clemson University in South Carolina, peonies need a soil pH of 6.5 to 7.0. Poorly draining soil also limits the ability for water to get down deep into the roots – tree peonies have particularly deep root systems. A higher or lower pH changes what nutrients are available in the soil. And when the soil pH is out side of the range 6.5 to 7.0 the nutrients that peonies thrive on aren’t as abundant.
Water also helps the roots to absorb nutrients and transport them through the plant. So, when the water doesn’t get all the way down to the roots a peony plant will suffer from a lack of nutrients and water. Which will generally show initially as yellow spots, or yellowing of the leaves. After some time the leaves will turn brown and die before the onset of winter when the leaves die back naturally. A soil testing kit can be purchased for very cheap at a garden supply store or online.
- Replant the peonies in free-draining soil that is loose, and dark brown in color.
- If the pH is over 7.0 add sulfur.
- If the pH is lower than 6.5 add limestone-based products – commonly known as lime.
Peonies are relatively pest-resistant. But, from time to time they can make a home on peonies and begin to sap the vital nutrients. Luckily they are very easy to spot and treat. The most obvious signs are spider-web-like structures on the underside of the leaves, bumps on the stems, and a brown/black residue crumbly residue forming on the plant.
The bumps are the bodies of scale insects that latch on and feed on the nutrients of the plant. Small white insects are mealybugs that produce white silk. Mealybugs will cause brown patches on the leaves where they have sucked out the nutrients. Whereas, scale insects sap out the nutrients over time weakening the plant. And when they are large number can completely kill a peony.
- After sunset spray the plant with an insecticidal spray or neem oil.
- If you notice a large infestation in the soil replant them into fresh soil.
Too many nutrients
Good soil for peony is the consistency of compost that you buy from a garden supply store. It’s generally not required to add additional fertilizer. It can be a good idea to add additional fertilizer to some plants, however, too much can have the opposite effect and damage the roots.
This reduces the number of nutrients that peonies can uptake and causes the leaves to develop yellow spots, and eventually turn brown. Signs of this are that some of the leaves are brown, whereas, others have yellow spots that haven’t yet turned brown.
- Replant them into fresh soil that is the texture of store-bought compost.
- Don’t add any additional fertilizers, which allows the soil to balance out.