dave said:It looks to me like it's suffering from stress. It looks like it is in virgin sandy and infertile soil, out in the hot sun, and dry.
The very best thing you can do is apply a generous layer (3 inches or so) of wood chip mulch all around it in a circle at least 3 feet wide. Don't put the mulch right up to the tree, though, give it a few inches to breath.
When dry, water the entire circle of mulch deeply about once a week. You want that soil to get drenched all the way down. The wood chips will then protect the moisture in the ground from quickly evaporating. The mulch will also cool the soil and provide even other benefits.
I don't wish to dismiss your assumption Dave, as you are practically considered a garden God among the wonderful people here. Yet, as the days come and go, one is to think that sun and water are not the issue. As I had mentioned, I too thought at first that thirst was the issue. So it was generously watered. Then the Summer rain storms began. And beneath that white, bleached sand (about two inches) there is a dark, cool soil that surprisingly stays moist even during drought. As it is with many Florida yards.
The plant in question receives about 9 hours of sun a day. Which, I believe such a proclaimed "tolerant" plant should be able to withstand.
The bare ground you see around the plant is an intentional act of herbicide. Now, I wonder if such a plant rumored with strength and toughness could have fallen sickly because of my (carefully attempted) herbicide-ing? I'm not sure. I've herbicided around trees, young and old, gardens, etc. for about five years now without ever a fatality.
I don't argue it could use some mulch. However, the Myrtle remains in the same shape and appearance seen in the photos above. As if it's in a perpetual state of suspended animation. Despite the rains, deceivingly fertile soil and perplexed stares that wish to will it to health, it remains a mystery. It has been so for nearly a full month. I feel there is nothing I can do but wait and wonder.
Such is life.