Norway Maple Issues


I have a 20ft high Norway Maple (probably the ‘Crimson King’ cultivar) that is starting to lose leaves, and now branches, on it’s lower west side. Trunk is 19″ circumfrance at 4ft. I first noticed some minor leaf loss about two years ago and more last year. On closer inspection last summer I saw a large dark spot, about a foot long, on the lower trunk. This spot is the same side of the tree where the leaf and branch loss is occuring. The bark is showing cracking in the middle of this spot. At times last summer the cracks were weeping fluid.

My neighbour has many crimson king norway maples on his property and I’ve noticed they have been declining as well the last few years.

My question is what is causing this? Is there a way to save this tree, or should I remove it and plant something new this spring?

See pictures below.


Thank you for your inquiry to the Toronto Master Gardeners about your ailing Norway Maple (Acer platinoides) tree.

The black bark may be the early signs of a canker developing, or a sign of another kind of fungal infection. There are several types of fungi that impact maple species that can cause blackening and splitting of the tree bark in maples, along with the other symptoms you reported, such as oozing, leaf loss and branch dye-back. Trees that are in poor health for any number of reasons, such as stress, soil compaction, wounds caused by the freeze-thaw action of frost, root girdling, pollution or nutrient issues, become susceptible to secondary fungal infections.

For a definitive diagnosis, an arborist should be consulted. An arborist can also provide insight into the structural integrity of the tree, and recommend whether the tree should be removed.

For additional information, including working with arborists in the City of Toronto: