What to do with leaves dropped from a diseased Norway maple


We live in Toronto Rosedale and have a small 1/4 Acre walled garden. We have a Locust tree, a Norway Maple a Japanese Maple a Sugar Maple and a Verbena all mature. As you can imagine the garden is filled with leaves in Autumn, about half the leaves from the Norway Maple are diseased. We are concerned that if we do not clear all the leaves Mold could develop and especially impact our B Balm and Peonies next year. Should we clear all the leaves before Winter, leave them alone and remove them in the Spring or just try to remove only the diseased Norway Maple leaves (a very difficult job)? Would appreciate your wisdom


Thank you for contacting Toronto Master Gardeners. Mold or powdery mildew is host specific so the disease on the Norway maples won’t spread to your bee balms or peonies.  It would be a challenge to separate the Norway maple leaves from the rest of the fallen leaves.  To reduce the spread of the disease to the Norway maples however, it is considered best practice to remove diseased leaves in the fall and put them in the garbage.  More significantly Norway maples are considered to be an invasive species and consequently the City of Toronto expects homeowners to put any Norway tree refuse in the garbage and not in the yard waste bags.

To prevent your bee balms and peonies from developing mold or powdery mildew

  • Space the plants for good air circulation.
  • Plant them in full sun.
  • Water the plants early in the day and try to avoid overhead watering.