Native Ornamental Grasses

Warm season and cool season

The single most useful distinction, and the one that explains why a new grass planting looks dead in May.

Warm-season grasses stay dormant until soil temperatures rise, then grow through the heat of summer and flower in late summer and fall. Big bluestem, switchgrass, indian grass, little bluestem, prairie dropseed, and the gramas are all warm season. They emerge late, and gardeners dig them up every spring assuming failure.

Cool-season grasses and sedges grow in spring and fall and go quiet in summer heat. Pennsylvania sedge is the example here, and it greens up early, which is what makes it useful as a lawn substitute.

Knowing which you have tells you when to cut it back and when to stop worrying.

Grasses hold a planting together

In a prairie, flowers grew embedded in a dense grass matrix. That matrix supported the flower stems physically, occupied the soil so weed seeds had nowhere to germinate, and gave the whole community a continuous texture.

A modern bed of flowers spaced in mulch has none of that, which is why it flops, why it weeds, and why it looks like a collection rather than a place.

Adding grasses between the flowers restores the function. Prairie dropseed and little bluestem work at the front, switchgrass and indian grass in the middle, big bluestem at the back or in a meadow.

Habitat value that is easy to miss

Grasses offer no nectar. They are wind pollinated and their flowers are not built for insects at all, so they never appear on pollinator plant lists.

They are nonetheless essential. Skipper butterflies, which are a large share of the butterflies in most yards, feed on grass foliage as caterpillars, along with many moths. A garden with abundant nectar and no native grasses supports adult butterflies and produces few.

Seed feeds sparrows, juncos, finches, and quail through fall and winter. Standing clumps give ground birds winter cover, and the dense bases shelter overwintering insects and sometimes bumblebee nests.

Cut back in spring, never in fall

This is the practical rule that follows from everything above.

A grass cut down in October loses its winter form, its seed, the shelter in its base, and the insects overwintering in it, all at once, in exchange for a tidy bed nobody is looking at.

Left standing, native grasses hold their structure through snow, turn gold and copper and amber, and keep feeding birds until March.

Cut back to a few inches in late winter, before new growth starts. For fine grasses like prairie dropseed, combing the dead foliage out by hand is faster and leaves the shape intact.

Sources: Lady Bird Johnson Wildflower Center, University of Texas at Austin (species profiles); US Department of Agriculture Natural Resources Conservation Service (warm and cool season grass management); Xerces Society (native grasses as lepidoptera hosts and overwintering habitat).