Hi, my herbal peony’s leaves are turning brown. I am in Toronto, Sunny spot. Could you please advice what I should do?
Thank you for contacting the Toronto Master Gardeners concerning your herbaceous peony.
Peonies are considered to be hardy, long-lived perennial however, peonies leaves can turn brown if certain cultural requirements are not met or if they become infected by a number of pathogens and pests that affect peony health.
Peonies subjected to prolonged periods of insufficient water and exposure to temperatures above 32C ( which is what we have recently experienced) may suffer from leaf scorch, or the browning of leaf tips and margins. is your peony being overwatered? Does it have proper drainage? Too much water or improper drainage leads to root rot and browning of leaves. Have you recently fertilized your peony? Over-fertilizing especially during the heat wave that we had can burn the plant’s leaves, causing them to turn yellow, then brown.
Peonies prefer to be sited in a location that receives a minimum of 6 hours of sun per day in well-drained, slightly acidic soil (6.5 to 7.0 pH). If your peony is planted in heavy, clay soil, amending with compost will help with the drainage and provide much needed organic nutrients to your plant. This website lists the proper growing requirements for your peony.
Brown leaves may also be a sign that your peony has become infected with leaf blotch, peony wilt or phytophthora blight. Phytophthora blight is caused by the fungus Phytophthora cactorum. The fungus attacks the stems and leaves of a peony, turning the tissue dark brown or black. Infected tissue becomes tough and leather-like. If your plant is infected with this fungus the best prevention is to remove and destroy infected plants and surrounding soil to stop the disease’s spread. Do not put the infected material in your composter, instead put it out for city pick up.
Peony wilt is an infection of the leaves and stem by the fungus Botrytis paeoniae. This disease generally appears in spring or early summer when the shoots of affected herbaceous paeonies wilt and turn brown for no apparent reason. Remove all infected material promptly and burn or send to landfill.
According to the Missouri Botanical Garden: ” Peonies are also subject to a variety of viruses including peony ringspot virus, leaf curl, Le Moine disease, crown elongation, tobacco ratlle virus and mosaic. Symptoms include a general dwarfing of the plant, lack of proper chlorophyll production resulting in a mottled appearance on foliage yellowing and in some cases rings on leaves as well as necrotic (dead) areas. These diseases can be spread by feeding insects or mites, or mechanically through hands and tools. Infected plants cannot be cured. Remove and dispose of infected plants.” If your peony is infected by any of these viruses make sure to sterilize your tools after you have removed the infected plant.
Here is an excellent article on TRV (tobacco rattle virus) along with photos. Lastely, this website lists all possible peony diseases along with a description of the disease, their cause and how to properly manage the disease.
Good Luck with your peony.