Problem with Pin Oak

Asked October 2, 2019, 10:33 AM EDT

What should I do to protect a Pin Oak that has very recently started to get brown leaves and has a darkened color from the ground up about 30 inches on the trunk? The tree, 1 of 3 Pin Oaks planted in my yard in Brunswick in December 2018, is about 12 ft tall and has some cracks in the bark that has become dark. There are also a few small, dark & cracked spots higher on the tree. I don't see this problem on the other 2 Pin Oaks. The tree looked great until very recently although I didn't take note if the bark was gradually becoming darker over time. I attached 3 photos to illustrate the problem. I would appreciate any advice you can provide.

Frederick County Maryland

1 Response

We looked at your photos. The tree is less than a year old and still trying to establish its root system. Looks like there is excessive mulch around the trunk and the tree can benefit from watering.
Excessive mulch reduces soil oxygen for the roots. The roots in their search for oxygen grow into the mulch. During drought the mulch dries out and the roots in the mulch die. When the mulch is piled up against the trunk the bark decays and there may be dieback. We recommend that you slope the mulch away from the trunk and feather it out. Do not let it touch the trunk. Mulch should be no thicker than several inches and away from the trunk.

The cracks in the trunk look like they may be from a type of stress such as poor site conditions, poor planting techniques, too much or not enough moisture, weaker root system, etc. we can not say for sure. There is nothing you can do to correct this.
The foliage does not look that bad. This tree will take about 3-4 years to establish a root system as it is a large tree. Keep the tree watered until the end of this season.

At this point, correct the mulch issue. Also, plants less than a year old should be watered deeply. Check the soil moisture weekly. The soil should be moist as a wrung out sponge. You may have to move the mulch and proble with a screwdriver. You will have to water up until the end of the season and during dry periods next season.

Here is more on the planting process, post planting care, and watering guidelines.