Mountain Laurel Disease or Fungus?

Asked May 31, 2020, 12:22 AM EDT

One of our mountain laurel plants has died. Another still has some leaves and even some flowers. What is wrong with the plant? Can it be diagnosed from the pattern on the leaves shown in the photos? Thank you!

Montgomery County Maryland

3 Responses

The flowers are beautiful and the foliage has leaf spots. We see this a lot. Mountain laurel are very susceptible to several leaf spots diseases and they are not easy to grow in our area. https://extension.umd.edu/hgic/topics/fungal-leaf-spots-shrubs

You did not mention how old the plant is and what site conditions they are located in. This plant requires an acid, cool moist, well drained soil in full sun to partial shade but grows best in the shade. When stressed due to environmental or cultural issues such as drought, excessive moisture, poor soils, poor drainage, etc. they can be susceptible to insect or disease problems.

Many leaf spot diseases can be tough on the plants but does not kill them. The yellow leaves with spots will fall off. If only a few leaves are affected, you can remove them. Otherwise, pick up any affected foliage from the ground to prevent any overwintering spores. Make sure mulch is no thicker than two inches in depth and keep away from the stems. Water deeply during dry periods if possible. No chemical controls are recommended.

Marian

Dear Marian,

Thank you for this fast reply. This Mountain Laurel is quite old. It was on our property when we bought it in 1999. I have added two photos that show more of the bushes. In the photo that shows multiple bushes - you can see the dead branches of one of the bushes on the left. Only about half the bush on the right is flowering. These bushes are in the shade.

I will work to remove the infected leaves from the bush and the ground as recommended. I have not done anything to help or change the soil in this area.

Thank you!
Jeanne

It's probably best to let them run their course, then, and replace them as they die off with alternatives. If you prefer natives and want to replant the area, options for shrubs include Summersweet (Clethra alnifolia), Viburnum (several species), Spicebush (Lindera benzoin), Carolina Allspice (Calycanthus floridus, a regional but not MD native), and Witchhazel (Hamamelis virginiana).

Miri