Japanese maple sapling with leaf rot?

Asked September 22, 2019, 12:48 PM EDT

My Young Japanese maple (Acer palmatum “Bloodgood”) was planted in June and appeared healthy until a few weeks ago, when the leaves began developing light-colored splotches and many leaves began to wilt and die. I have tried to keep it well watered. No direct sighting of bugs but some leaves appear to have been chewed. The soil and lawn surrounding the sapling are prone to periodic mushroom sprouts. Should I be feeding this tree with supplements?

Montgomery County Maryland

1 Response

Hi - Since you just planted your tree recently, in June, it is still getting established. It can take 12-18 months for a tree's root system to get fully established in the native soil, and watering during this period is critical. Also, the high heat we are having will increase a plant's water needs, but you also want to be careful that you don't overwater. Please see our watering guidelines.

Newly planted trees do not benefit from fertilization. We do not recommend using any fertilizer at this time. https://extension.umd.edu/hgic/topics/fertilizing-trees-and-shrubs

It looks like there is some minor powdery mildew on the leaves. https://extension.umd.edu/hgic/topics/powdery-mildew-trees-and-shrubs
This is not something you need to treat now. The leaves will drop soon; just rake them up and discard them.

Japanese maples are shallow-rooted plants and can be sensitive to soil moisture, heat, frost, etc. We recommend a light layer of mulch around the base of the tree (no more than 2-3" deep and avoid putting it right up against the trunk).

Assuming the tree was planted correctly (not root-bound in the pot, roots spread out in the planting hole), you need to allow more time for the tree to get established. Some plants go through a period of what is referred to as "transplant shock" and leaf scorch (browning leaf tips) is a symptom of that. Here is more information, https://www.extension.purdue.edu/extmedia/bp/bp-31.html.

Also, please refer to our article about the conditions for growing Japanese maples successfully: https://marylandgrows.umd.edu/2018/08/24/japanese-maples-in-maryland-landscapes-plant-location-care-...