This condition of browning leaves is called leaf scorch.
Leaf scorch looks like browning or greying of the leaf margins.
Leaves may appear dead and brittle.
Missouri Botanical Garden
You may also notice yellowing or darkening of the areas between the main leaf veins.
Leaf scorch is most often because of over-exposure to the sun.
This leaf condition can vary in terms of severity.
As the condition worsens, browning extends throughout the leaf, affecting more of the leaves.
Bright, direct sunlight every day, all day, is usually too much for a Japanese maple tree.
you’re able to mitigate leaf scorch by making sure to water them adequately during dry spells.
A deep watering done less frequently is better than more frequent, shallow watering.
The goal is to have the soil evenly moist, not soggy or overwatered.
Compost is safe to apply at any time and will not harm the plant.
As for pesticides, only use them as a last resort and according to package instructions.
Exposure to Intense Environmental Factors
Harsh winters can damage, injure, or destroy roots.
High winds can also draw moisture out of plant tissues drying them out.
Remember, a tree that has leaf scorch is not a death sentence.
Leaf scorch is the tree’s defense mechanism.
Your tree has secondary buds that will produce a second set of leaves.
Leaf Scorch.Colorado State University Extension
Fertilizer or Pesticide Burn on Vegetable Leaves.
University of Maryland Extension.
