Grooming Ornamental Grasses: When & How to Cut Back for Best Looks

Ornamental grasses add grace and texture to borders and meadows but need periodic shearing or thinning to avoid an unsightly mix of new and dead growth. Landscape designer Michelle Comeau (Carmel, CA; 831-620-0111) matches method to grass type—warm-season (deciduous) or cool-season (evergreen)—and trims at the right time.

Deciduous (Warm-Season) Grasses

Foliage browns in fall; plants go dormant. Winter silhouettes are majestic—wait until late winter/early spring (new growth at base) to cut back. (In high fire-risk areas, cut when brown.) Divide large old clumps: dig, saw rootball vertically into halves/quarters, replant immediately.

Evergreen (Cool-Season) Grasses

Foliage stays green through winter (cold snaps may kill tips). Some semievergreen (e.g., feather reed grass). Cut back late winter/early spring. Divide old clumps fall, winter, or spring.

What to Do Now

Deciduous Grasses

Using sharp hedge/shear shears, cut laterally section by section, leaving a small mound. Shear small grasses (≤3 ft.) to 1½–3 in.; large (3–6 ft.) to 4–6 in.

Common: eulalia (Miscanthus), fall-blooming reed grass (Calamagrostis brachytricha), fountain grass (Pennisetum orientale 'Karley Rose'), Japanese forest grass (Hakonechloa macra).

Evergreen Grasses

Selectively cut dead growth with pruners or comb out with fingers. Prune brown tips or cut back by ⅓ to renew/shape. Carex texensis, C. tumulicola, Festuca mairei can take ⅔ cutback.

Common: blue oat grass (Helictotrichon sempervirens), feather reed grass (Calamagrostis × acutiflora 'Karl Foerster'), rush (Juncus), sedge (Carex).