How to make grasses shine in Autumn gardens!

Showy warm season grasses flower in late summer and fall.
Molinia 'Cordoba' in left foreground;
Miscanthus in back center; Cool season ribbon grass in right foreground
has no flowers and growth has slowed.
Photos: Mary Meyer, Extension Horticulturist

While many perennials are past their prime by the end of September, landscape grasses are at their peak in the fall, with showy flowers and fall color. Warm season grasses, including miscanthus, big and little bluestem, switchgrass and prairie dropseed are in full flower and tallest height with the warm days of summer and fall. Enjoy the flowers and motion of grasses as they sway in the breeze!

Here's why you shouldn't cut them back!

Grasses should not be cut back in the fall. Leave the flowering stems up to enjoy through the winter. Fall cutback may increase the chance of winter injury on grasses and is not recommended for Minnesota gardeners. Birds, bees and other wildlife appreciate the cover of grasses in the winter.

My grasses don't look healthy

If you have a grass with few flowers, or shorter plants with dead sections, these are indications that the plant should be divided, a good project for next spring.

Yellow stems showing mice damage on purple moregrass, Molinia.
Photo: Mary Meyer, Extension Horticulturist

If you notice dead or yellow stem on some of your grasses, check closely for mice or rodent damage. Mice love to live under the protection of thick bunch grasses, like prairie dropseed. Mice bait or repellents may be necessary if you see significant damage.

Grasses that are floppy and falling over may need to be moved to full sun locations or have reduced water or fertilizer. Once established most grasses need little supplemental water and actually grow better with no additional fertilizer.

Planting tip: Add variety of grasses to your garden

For the most variety and longest season of bloom, plant both cool and warm season grasses. Cool season grasses like Karl Forester feather reedgrass and tufted hairgrass, bloom in late spring and early summer and their tops are brown by the fall. Warm season grasses like miscanthus and little bluestem flower in late summer and do not turn brown until frost.

Author: Mary Meyer, Extension Horticulturist