Q.Purple fountain grass
When does the purple fountain grass start to come back? I cut mine down and the winter was very mild.
Depends on what zone you're in. If it isn't showing signs of life by now, there's a good chance it may not come back, especially if this is the first winter you've had it (meaning you haven't had it long enough to establish "about" when you should be seeing new growth). This article may help you: https://www.gardeningknowhow.com/ornamental/foliage/purple-fountain-grass/grow-purple-fountain-grass.htm