Ask Mr. Smarty Plants

If you have not noted any damage from either mowing or edging tools, nor has any pesticide been applied too near it, we are at a loss. Here are the Growing Conditions for Muhlenbergia capillaris (hairawn muhly), also known as Gulf Muhly:

Water Use: High
Light Requirement: Sun
Soil Moisture: Moist
Soil Description: Sandy soils. Sandy, Sandy Loam
Conditions Comments: In the fall, gulf muhly creates a stunning pink to lavender floral display. It functions well in meadow gardens and as a general garden plant.

If the soil hasn't changed, which surely it has not, another possibility that comes to mind is that some other nearby plant, a tree or shrub, perhaps, has grown enough to be shading the particular plant you are concerned with. Also, we noted in other research that, while this grass likes a moist soil, it can get rot problems with too much water standing on it. This grass blooms in October in Central Texas, but the pink/purple inflorescence lasts well through the Winter, and then should be cut down to about 6" and cleaned up to prevent insects hiding in the dead grass stems and perk up the plant. Another thing we could not find an answer for is how long do these grasses normally live? Since they propagate themselves by wind-blown seeds, as well as by bunching, rather than having stolons on the ground, it might not be noticeable in a field of Gulf muhly that some of them had died. But in a garden situation, one plant failing to thrive would be very noticeable. If you have trimmed your grass and it is starting to show new growth, we would suggest you check for soil moisture and sun exposure, correct either or both, if necessary, and give the grass another year to recover. 

From our Native Plant Image Gallery:

Muhlenbergia capillaris

Muhlenbergia capillaris

Muhlenbergia capillaris

Muhlenbergia capillaris