Japanese Maple, Acer palmatum 'Garnet' and 'Tamuke Yama' - Ask Extension
Hello, I have 2 Japanese Maples. One is cultivar 'Garnet' in mostly full sun, about 25 yrs old, the other is cultivar 'Tamuke Yama' in mostly shade, m...
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Japanese Maple, Acer palmatum 'Garnet' and 'Tamuke Yama' #944082
Asked September 02, 2026, 1:55 PM EDT
Hello, I have 2 Japanese Maples. One is cultivar 'Garnet' in mostly full sun, about 25 yrs old, the other is cultivar 'Tamuke Yama' in mostly shade, maybe 20 yrs old. After winter this year about 2/3 of Garnet was dead. I trimmed it up and it began to leaf out nicely. However now the leaves do not look good. This problem has been here for the last few yrs but not to this extent. I thought too much sun but now I think it's could be something else b/c Tamuke Yama also seems to be showing this problem and it is not in too much sun.
The first picture shows the Garnet, the second shows a back side of a Garnet leaf. The third picture shows the Tamuke Yama.
thank you!
Howard County Maryland
Expert Response
Winter dieback on Japanese maple is not uncommon, unfortunately, and it may result from either the ongoing drought at the time, opportunistic infections (which take advantage of stressed plants, such as Botryosphaeria canker), or damage to the cambium (the living tissue layer just under the thin bark) from a warm spell followed by a freeze. Too much cambium injury can kill branches or a large section of a canopy because those tissues transport sap (which contains nutrients and carbohydrate) and moisture.
Pruning off dead wood (branches that never leaf out) in spring is all you can do at that point, other than making sure the plant is watered as needed in any future dry spells. Insufficient moisture during winter can cause more damage than the cold itself in some situations, although temperature fluctuations can be damaging if they make the plant lose some hardiness as it breaks dormancy in response to early warmth.
The leaves pictured look typical for this time of year, and Japanese maple foliage is vulnerable to powdery mildew and other fungi, like anthracnose, both of which are common. The leaves pictured appear to be affected by anthracnose, even though it can be hard to visually distinguish from powdery mildew when the anthracnose-infected leaf tissue looks whitish or silvery. There is no fungicide we'd recommend using at this time, since it's very late in the season and comparatively minor infections like these aren't damaging the plant much, despite being an eyesore. While a fungicide spray starting next spring might suppress infection, it would need regular reapplication and the residue might harm other organisms, so it might not be worth the added cost and hassle. (Plus, if rain interrupts the spray schedule, infection could still take place, making treatments not as effective because it gives the fungi an opportunity to infect.)
You can rake up the leaves when they fall this autumn and dispose of them (don't compost) to help remove infectious spores that might otherwise overwinter around the base of the trees. Good air circulation helps to dry off leaf surfaces faster after rain, dew, or irrigation, reducing the risk of infection, but there's only so much influence you'd have over air circulation for established plants that can't easily be moved, or when it's not practical to prune out more of the canopy to improve airflow. Ironically, a sunnier exposure may help to keep leaves drier by speeding-up the evaporation of water on the leaves, but it can also stress laceleaf maples like these and contribute to "burnt"-looking leaf tips (called scorch damage) due to the hotter conditions during summer, especially in drier weather.
Miri
Pruning off dead wood (branches that never leaf out) in spring is all you can do at that point, other than making sure the plant is watered as needed in any future dry spells. Insufficient moisture during winter can cause more damage than the cold itself in some situations, although temperature fluctuations can be damaging if they make the plant lose some hardiness as it breaks dormancy in response to early warmth.
The leaves pictured look typical for this time of year, and Japanese maple foliage is vulnerable to powdery mildew and other fungi, like anthracnose, both of which are common. The leaves pictured appear to be affected by anthracnose, even though it can be hard to visually distinguish from powdery mildew when the anthracnose-infected leaf tissue looks whitish or silvery. There is no fungicide we'd recommend using at this time, since it's very late in the season and comparatively minor infections like these aren't damaging the plant much, despite being an eyesore. While a fungicide spray starting next spring might suppress infection, it would need regular reapplication and the residue might harm other organisms, so it might not be worth the added cost and hassle. (Plus, if rain interrupts the spray schedule, infection could still take place, making treatments not as effective because it gives the fungi an opportunity to infect.)
You can rake up the leaves when they fall this autumn and dispose of them (don't compost) to help remove infectious spores that might otherwise overwinter around the base of the trees. Good air circulation helps to dry off leaf surfaces faster after rain, dew, or irrigation, reducing the risk of infection, but there's only so much influence you'd have over air circulation for established plants that can't easily be moved, or when it's not practical to prune out more of the canopy to improve airflow. Ironically, a sunnier exposure may help to keep leaves drier by speeding-up the evaporation of water on the leaves, but it can also stress laceleaf maples like these and contribute to "burnt"-looking leaf tips (called scorch damage) due to the hotter conditions during summer, especially in drier weather.
Miri
