Japanese Maple has dying limbs. - Ask Extension
My Japanese Maple has limbs that are dying and a strange growth on the major limbs and trunk in some areas.
Knowledgebase
Japanese Maple has dying limbs. #873941
Asked June 20, 2024, 2:16 PM EDT
My Japanese Maple has limbs that are dying and a strange growth on the major limbs and trunk in some areas.
Baltimore County Maryland
Expert Response
The growths pictured on bark close-up are lichen and moss, which are quite common on older trees and are harmless. If you happen to irrigate the tree's root zone using a sprinkler that wets the bark, that might be contributing to the proliferation of lichen and moss, though they don't need controlling or removal since they don't damage the tree.
The branch dieback could have several causes. Japanese Maples, if stressed by drought, high heat, or other environmental conditions, could be infected by opportunistic pathogens like Botryosphaeria canker. No cure exists, but dead or dying branches should be trimmed off promptly. Make sure cuts are made in the right location so wood is not removed flush with the trunk (or with the next-closest branch); the linked page has a diagram and video link that may be helpful to illustrate where to prune.
The trunk appears to be either planted too deeply or over-mulched, since we can't see a root flare. Such situations can pose a long-term threat to tree health, especially since maples as a group are prone to developing girdling roots in those circumstances. Girdling roots could contribute to some branch dieback when the condition is advanced. We can't say if this is happening here, but it is worth investigating. Not all girdling roots can be corrected.
We don't see any in the photos, since they aren't close-ups of the smaller-diameter dead branches, but you can also look for the presence of scale insects. In particular, the aptly-named Japanese Maple Scale is the most common type infesting these trees, and heavy populations can cause branch decline and dieback over time. Just because branches are dying doesn't mean scale are the culprit, especially if you don't see any on the bark, but we mention it so you can check.
For now, just cut off all dead or mostly-dead branches, and keep monitoring the tree for watering needs as we move through summer and fall. Japanese Maples prefer to stay somewhat evenly moist, especially if growing in full sun and our mid-Atlantic heat, though they can handle a mild amount of drying out (that is, they don't need to stay damp constantly) before becoming drought-stressed.
Miri
The branch dieback could have several causes. Japanese Maples, if stressed by drought, high heat, or other environmental conditions, could be infected by opportunistic pathogens like Botryosphaeria canker. No cure exists, but dead or dying branches should be trimmed off promptly. Make sure cuts are made in the right location so wood is not removed flush with the trunk (or with the next-closest branch); the linked page has a diagram and video link that may be helpful to illustrate where to prune.
The trunk appears to be either planted too deeply or over-mulched, since we can't see a root flare. Such situations can pose a long-term threat to tree health, especially since maples as a group are prone to developing girdling roots in those circumstances. Girdling roots could contribute to some branch dieback when the condition is advanced. We can't say if this is happening here, but it is worth investigating. Not all girdling roots can be corrected.
We don't see any in the photos, since they aren't close-ups of the smaller-diameter dead branches, but you can also look for the presence of scale insects. In particular, the aptly-named Japanese Maple Scale is the most common type infesting these trees, and heavy populations can cause branch decline and dieback over time. Just because branches are dying doesn't mean scale are the culprit, especially if you don't see any on the bark, but we mention it so you can check.
For now, just cut off all dead or mostly-dead branches, and keep monitoring the tree for watering needs as we move through summer and fall. Japanese Maples prefer to stay somewhat evenly moist, especially if growing in full sun and our mid-Atlantic heat, though they can handle a mild amount of drying out (that is, they don't need to stay damp constantly) before becoming drought-stressed.
Miri
