A clumping ornamental grass native to the eastern United States, pink muhly grass (Muhlenbergia capillaris) grows thin, threadlike leaves in a mound. Wispy pink plumes appear in very late summer and persist for months. Grow this grass in U.S. Department of Agriculture hardiness zones 5 though 10.
Expect pink muhly grass to mature to a height of 2 to 4 feet. The width of the mop-like mound of leaves is slightly wider, perhaps 30 to 60 inches.
Typically gardeners cut back old grass foliage in early spring to a height of 6 inches. The pink muhly grass rejuvenates over spring and summer. Only when the upright flower plumes occur in late summer does the grass reach its tallest size. In winter the dried seed plumes will flop over from rain, wind and heavy snow.
The Learn2Grow plant database comments that pink muhly grass does not grow as tall, large or robustly in nutrient-poor or dry soils. Plants older than 4 years that have never been divided can create flower plumes even 4 to 5 feet tall. Young, newly planted grasses do not mature as tall their first year and become taller as the roots establish in the second growing season.