Ornamental grasses have gained popularity in recent years due to their low maintenance and potential for year-round interest in the garden. These plants also respond beautifully to the wind and create sound with their rustling leaves. True grasses are in the Grass family (Poaceae) but horticulturists consider Sedges (Carex spp.) within the group of ornamental grasses. Late summer is the season commonly associated with grasses, but many grasses actually put on their growth during the cool temperatures of spring and fall. Grasses are classified into two groups of growth seasons (Cool Season and Warm Season) based on what soil temperatures are most conducive to their growth.
COOL SEASON ORNAMENTAL GRASSES
Cool Season ornamental grass species are adapted to grow best during the cooler temperatures (50-75*F) of early spring and fall. Some will have several growth spurts throughout the season dependent on temperature. These plants have the benefit of giving a show in spring with their early foliage and then give a second show with seed heads by mid-summer. Planted in masses, they can provide an excellent backdrop for spring/early summer flowers. During the heat of late summer, these species may “melt out” and go dormant. This is not harmful to the plant; it is a natural response to heat and drought. Many will perk up during the cool weather of fall.
Here are some examples:
Sedge (Carex spp.) Sedge is not a true ornamental grass but a grass-like plant with many varieties and cultivars of various sizes, textures, and shades of colors. All require adequate moisture, especially when growing in full sun. Some are semi-evergreen Full sun to shade.
Autumn Moor Grass (Sesleria autumnnalis) have airy silver inflorescences the sway in the wind above the compact foliage. It is a great groundcover for areas with a lot of root competition. Sun to moderate shade.
Feather Reed Grass (Calamagrostis x acutiflora) is an early bloomer is one of the largest cool season grasses. Its flower stalks rise to 4-5’ in strictly vertical lines. Tolerates wet soils. Full sun.
Northern Sea Oats (Chasmanthium latifolium) bears Large, graceful seed heads in arching spikes that rise above very early foliage. Tolerates poor, dry soils, but does best with adequate moisture. Will naturalize in optimal soil conditions. Sun to moderate shade.
Tufted Hair Grass (Deschampsia cespitosa) has hairy masses of finely-branched cloudlike inflorescences that sway in the wind above neat tufts of bright green foliage. Semi-evergreen, native to Illinois wet grasslands. Sun to moderate shade.
WARM SEASON ORNAMENTAL GRASSES
Warm Season ornamental grass species are adapted to grow best during the summer heat (75-90*F). This means that they take longer to emerge in spring while they are waiting for the temperatures to be consistently warm. While they do not add much to the spring flower show, they do look good all summer and fall. Of course, they pair well with plants that peak later, such as Coneflower and Garden Phlox. These grasses are useful because they have beautiful seed heads in the late summer-fall, when many other herbaceous plants are past their prime. Their seed stalks will remain upright all winter unless they are weighed down with heavy snow.
Here are some examples:
Hakone Grass (Hakonechloa macra) resembles a waterfall, with its fountain like-habit. Tolerant of some shade, the gold forms pair great with blue Hostas. Requires adequate moisture. Partial sun to moderate shade.
Little Bluestem (Schizacyrium scoparium) is a striking Illinois prairie native that offers bluish foliage and excellent fall color. Requires well-drained, dry soils. Full sun.
Maiden Grass (Miscanthus sinensis) is a large ornamental grass. Many variegated cultivars of this species really make a statement in the garden. Full sun.
Purple Love Grass (Eragrostis spectabilis) has sprays of tiny reddish flowers that rise above the foliage like a haze of smoke. Does well in dry soils. Full sun.
Prairie Dropseed (Sporobolus heterolepis) is a small ornamental grass with handsome, finely textured foliage. Lightly fragrant, airy seed heads especially look great when backlit. Native to Illinois prairies. Full sun.
Sideoats Grama (Bouteloua curtipendula) has copper-red seeds that form along one side of its stems. A mass planting looks sensational. Native to Illinois prairies. Requires well-drained, dry soils. Full sun.
Switchgrass (Panicum virgatum) makes an excellent backdrop in the perennial garden, this species also has great fall color. Native to Illinois prairies. Full sun.
Ornamental grasses as a group can add unique forms and textures during many seasons in the garden. When combining grasses with other ornamental plants, we consider the peak time of both species. A balance between cool season and warm season grasses can create continual interest through the growing season. Do you love what ornamental grasses add to the garden? Check out our garden design portfolio for more ideas.