Grasses, sedges & ferns

Three different plants, grouped by what they do

Grasses are wind-pollinated flowering plants with narrow leaves and round hollow stems. Sedges look similar and are a separate family: their stems are solid and triangular, which is where the old line about sedges having edges comes from. Ferns are older than both and do not flower at all, reproducing by spores.

They are grouped here because they do the same job in a planting. They supply texture, structure, and ground-level cover, and they occupy the space between the flowers.

The warm season and cool season split

This explains the single most common panic about a new native planting.

Warm-season grasses stay dormant until the soil warms, often showing little growth until late May, then grow hard through summer heat and flower in late summer and fall. Big bluestem, indian grass, switchgrass, little bluestem, prairie dropseed, and the gramas are all warm season. Every spring, somebody digs one up assuming it died.

Cool-season plants grow in spring and fall and rest in summer heat. Pennsylvania sedge is the example here, and its early greening is exactly what makes it work as a shade lawn.

Why they matter to wildlife

Grasses offer no nectar and their pollen is not intended for insects, so they are absent from every pollinator plant list. That absence is misleading.

Skipper butterflies, which are a large share of the butterflies in most yards, feed on grass and sedge foliage as caterpillars, as do a great many moths. A garden with abundant nectar and no native grasses supports visiting adults and produces very few of its own.

Seed feeds sparrows, juncos, finches, and quail through fall and winter. Standing clumps are winter cover for ground-feeding birds, and the dense tufted bases shelter overwintering insects and sometimes bumblebee nests. Christmas fern's evergreen fronds flatten into a layer of ground cover that salamanders and insects use.

What they do for a planting

In a prairie, flowers grew embedded in grass, which held their stems upright, shaded out weed seedlings, and gave the whole community continuity. A bed of flowers spaced in mulch has none of that, and it flops, it weeds, and it reads as a collection rather than a place.

Ferns and sedges do the same work in shade, where they carry the composition for the eleven months the spring flowers are not doing anything.

Cut them back in late winter, never in fall. Cutting in October costs the winter form, the seed, the shelter, and the insects overwintering inside, in exchange for tidiness in a season nobody is out looking.

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 identification and management); Xerces Society (native grasses and sedges as lepidoptera host plants and overwintering habitat).