My purple fountain grass has wilted after rainfall.
Purple Fountain Grass
Certified GKH Gardening Expert
If you have received a lot of rainfall or if the drainage is poor, the roots could be suffocating. I would recommend that you check your drainage. If the drainage is poor, take steps to improve it. This can be done by layering on compost about 2-3 inches every 1-2 months. It will work its way into the soil around the plant.