Low, spreading grasses can carpet a bank or fill a difficult area where lawn struggles. Ornamental grasses for ground cover include prairie dropseed (Sporobolus heterolepis), blue fescue (Festuca glauca), sedges in damp shade, and low switchgrass types planted in a tight grid. Massed close together, these knit into a textured mat that suppresses weeds once established. I space them so the clumps just touch at maturity, which fills the area within a season or two without leaving gaps for weeds. The advantage of ornamental grasses for ground cover over a traditional groundcover is the movement and the fall color, plus they need no mowing. Sedges handle the shaded, moist spots where most grasses fail, while dropseed and fescue take the dry, sunny banks. A single cut-back in late winter is the only annual maintenance the planting asks for.
What “ground cover” means for an ornamental grass
Most ornamental grasses are clump-formers, not spreaders. They do not run by rhizome the way a lawn grass or a vinca does. To make a clump-forming grass work as a ground cover, you plant many clumps close together so they knit into a continuous mass. The visual effect is the same as a true spreading ground cover, but the work is at planting time, not at maintenance time.
This works for any compact, clumping grass. Blue fescue at 12-inch (30 cm) spacing forms a tight carpet in one season. Prairie dropseed at 18-inch (45 cm) spacing forms a fine-textured mat in two seasons. Sedges at 12 to 18 inches (30-45 cm) handle shaded, moist spots where the true grasses struggle. A drift of dwarf switchgrass at 18 to 24 inches (45-60 cm) gives a wilder, taller cover for larger areas.
The only ornamental grass that truly spreads as a ground cover is Acorus gramineus (Japanese rush), and even that is a slow spreader. Everything else requires planting in mass.
The best ground cover grasses for cold climates
A short list covers most ground cover situations. Each has a different look and a different tolerance for sun, shade, and moisture, but all are hardy in USDA zones 3 to 5 and form dense mats when massed.
Blue fescue (Festuca glauca) is my top pick for tight spaces. It forms 6 to 12 inch (15-30 cm) blue-gray tufts that knit together into a low carpet when planted 8 to 12 inches (20-30 cm) apart. Hardy in USDA zones 4 to 8, it tolerates lean soil, dry conditions, and reflected heat better than almost any perennial I know. The catch is that the centers die out after 2 to 3 years, so the planting needs regular division to stay full. I lift and replant the tufts every 3 years and the carpet stays tight.
Prairie dropseed (Sporobolus heterolepis) is the native fine-textured choice. Its 24 to 36 inch (60-90 cm) fine-textured fountain mounds knit together at 18 to 24 inch (45-60 cm) spacing into a graceful, swaying mat. Hardy in USDA zones 3 to 9, it tolerates clay and drought and has a faint coriander-like fragrance at bloom in late summer. The fall color is a soft golden bronze that lights up an autumn garden.
Sedges (Carex spp.) are the shade and moisture picks. Most are technically not true grasses, but they are grass-like in form and function. Carex morrowii (Japanese sedge) and Carex oshimensis (Japanese sedge, often sold as C. hachijoensis) form 12 to 24 inch (30-60 cm) evergreen or semi-evergreen clumps in shade. Hardy in USDA zones 5 to 9 (some cultivars to zone 4), they handle the moist, shaded conditions under trees where most true grasses fail. Carex pensylvanica (Pennsylvania sedge) is the native lawn alternative for dry shade, spreading slowly by rhizome to form a 6 to 12 inch (15-30 cm) mat in zones 3 to 8.
Dwarf switchgrass ‘Shenandoah’ (Panicum virgatum ‘Shenandoah’) is the upright native pick. At 36 inches (90 cm) tall and 24 to 30 inches (60-75 cm) wide, it forms a wilder ground cover than the compact types, but it tolerates the same conditions as a full-size switchgrass and brings strong wine-red fall color. Hardy in USDA zones 3 to 9, it works for a large area where a low carpet would feel out of scale.
Dwarf fountain grass ‘Hameln’ (Pennisetum alopecuroides ‘Hameln’) is the showy pick for smaller areas. Its 24 to 36 inch (60-90 cm) arching mounds with bottlebrush plumes knit together at 18 to 24 inch (45-60 cm) spacing into a flowing, mounded cover. Hardy in USDA zones 5 to 9, it can struggle in colder zones without protection.
| Blue fescue (Festuca glauca) | 6-12 in (15-30 cm) | 8-12 in (20-30 cm) | Full sun | 4-8 | Divide every 2-3 years |
| Prairie dropseed (Sporobolus heterolepis) | 24-36 in (60-90 cm) | 18-24 in (45-60 cm) | Full sun | 3-9 | Annual late-winter cut |
| Pennsylvania sedge (Carex pensylvanica) | 6-12 in (15-30 cm) | 8-12 in (20-30 cm) | Part to full shade | 3-8 | Slow, divide if needed |
| Japanese sedge (Carex morrowii) | 12-24 in (30-60 cm) | 12-18 in (30-45 cm) | Part shade | 5-9 | Comb out dead blades |
| Switchgrass 'Shenandoah' (Panicum) | 36 in (90 cm) | 18-24 in (45-60 cm) | Full sun | 3-9 | Annual late-winter cut |
| Fountain grass 'Hameln' (Pennisetum) | 24-36 in (60-90 cm) | 18-24 in (45-60 cm) | Full sun | 5-9 | Annual late-winter cut, may need protection in zone 5 |
Spacing for fast fill-in
The closer you plant, the faster the cover fills in, but the more plants you need. I aim for the spacing at which the clumps just touch at maturity, then plant slightly closer in the first season to give the cover a quick start.
Blue fescue planted 8 inches (20 cm) apart fills in within one season. Planted 12 inches (30 cm) apart, it takes two seasons. The closer spacing costs more in plants but gives a finished look faster. For a 50-square-foot (4.5 sq m) area at 12-inch spacing, I need about 50 plants. At 8-inch spacing, I need about 110.
Prairie dropseed at 18-inch (45 cm) spacing takes about two seasons to fill in. Planted 24 inches (60 cm) apart, it takes three seasons. The two-season fill is the practical target, and I plant slightly closer in heavy clay where root growth is slower.
Sedges vary. Carex pensylvanica spreads slowly by rhizome, so a 12-inch (30 cm) spacing can take three seasons to knit together. The wait is worth it, since the native sedge lawn alternative handles dry shade under mature trees better than almost anything else in my garden. Carex morrowii clumps rather than spreads, so it needs the closer 12-inch (30 cm) spacing to form a continuous mat.
Sun versus shade
Most ground cover grasses want sun. Blue fescue, prairie dropseed, dwarf switchgrass, and dwarf fountain grass all want at least six hours of direct sun for tight form and good color. In shade they stretch, lean, and lose their fall color.
For shade, the answer is sedges. Pennsylvania sedge handles dry shade under deciduous trees and forms a lawn-like mat at 6 to 12 inches (15-30 cm). Japanese sedge (Carex morrowii and C. oshimensis) handles moist shade and forms 12 to 24 inch (30-60 cm) evergreen clumps. Both are hardy enough for zone 5 with good siting, though Japanese sedge benefits from a sheltered spot in colder zones.
A useful mix for a shaded slope is Pennsylvania sedge in the dry upper area and Japanese sedge in the moister lower area. Both knit together into a flowing green mat that needs no mowing and handles tree-root competition where few other ground covers can.
Weed control while the cover fills in
The first two seasons are the weedy ones. The young grass clumps have not yet shaded the soil, and any open ground between them is a weed opportunity. I mulch between the young plants with 1 to 2 inches (2.5-5 cm) of fine bark or shredded leaves, which suppresses annual weeds while the grass fills in.
By year two or three, the clumps knit together and the mulch is no longer needed. The dense mat of grass roots and thatch shades the soil and out-competes most weed seeds. A few persistent weeds may show up, but hand-pulling or spot treatment handles them.
The one weed I watch for is quack grass (Elymus repens), which can run rhizomes through a young grass planting before the clumps knit together. I pull any quack grass I see in the first two seasons, and I am ruthless about it. Once the planting fills in, the quack grass cannot compete.
In 2019 I planted a 60-square-foot (5.5 sq m) area at the front of my perennial border as a test: blue fescue ‘Boulder Blue’ at 10-inch (25 cm) spacing, about 90 plants. The first year was a sea of mulch with little blue tufts poking through. The second year the tufts had grown and most had touched their neighbors, but the centers were already starting to die out and the gaps between rows were still weedy. By the third year I had divided the worst-centered tufts and replanted the divisions into the gaps, and the carpet finally read as a single mass. By year four, the carpet was full and tight, with no gaps and no mulch. The lesson is that a grass ground cover takes three years to look finished, and the work is in the first two seasons.
The annual routine
A grass ground cover needs almost nothing once established. The annual routine is one task: cut warm-season types down to a few inches in late winter, just before new growth pushes up. For evergreen sedges, comb out the dead blades by hand rather than cutting.
No fertilizer. No supplemental water after establishment. No mowing. No edging. The lean-soil, hands-off approach that suits ornamental grasses in any setting is even more valuable in a ground cover, where the goal is a self-sustaining mat.
The one thing I do add is an annual refresh of mulch in any gap that opens up. A gap in a ground cover planting is an open invitation for weeds, and a handful of shredded leaves or fine bark dropped into the gap keeps it closed until the surrounding grass fills in.
Why use grasses instead of traditional groundcovers
Traditional ground covers like pachysandra, ivy, and vinca are evergreen and dense, but they have a flat, static quality. A grass ground cover moves in the wind, catches the light differently through the day, and changes color through the seasons. The fall color of a prairie dropseed mat or the coppery red of a little bluestem carpet is a far more interesting visual than a static green mat.
Grasses also need less care than most traditional ground covers. Pachysandra benefits from annual fertilization and occasional division. Ivy needs regular trimming to keep it in bounds. Vinca can spread aggressively into lawn areas. A grass ground cover sits where you plant it, asks for nothing, and improves rather than degrades over the years.
For difficult sites, grasses are often the better choice. A dry, sunny bank that would need constant watering for vinca handles a drift of blue fescue or prairie dropseed with no supplemental water after establishment. A shaded, rooty area under trees where pachysandra struggles handles a carpet of Pennsylvania sedge with no supplemental water at all. The right grass in the right spot outperforms the traditional ground cover for less work.