What “non-invasive” really means
Gardeners usually mean one of three things when they ask for a grass that will not take over:
- It does not run. Running grasses spread by underground rhizomes or surface stems and can form large colonies. Clumping (bunch) grasses grow as a tuft that slowly widens.
- It does not seed around. Some clumpers drop large amounts of viable seed, and the seedlings can turn up in beds, lawns and nearby natural areas.
- It is not listed as invasive locally. A plant that is well behaved in one region can be a serious weed in another.
Most ornamental grasses are clumpers. A clump can still get wider over the years, but it should not wander through the garden. The seeding question is the one to check.
Clumping grasses that stay put
These are widely recommended as well-behaved clumpers. Heights are typical ranges and vary by cultivar.
- ‘Karl Foerster’ feather reed grass (Calamagrostis × acutiflora): upright, roughly 3 to 5 feet tall, and generally described as sterile, so it does not reseed.
- Pink muhly grass (Muhlenbergia capillaris): about 3 feet tall with pink flower clouds in fall. A tidy, drought-tolerant mound.
- Little bluestem (Schizachyrium scoparium): a native bunchgrass, about 1.5 to 4 feet depending on the cultivar, with fall color in copper and red.
- Prairie dropseed (Sporobolus heterolepis): a fine-textured native, about 2 to 3 feet, forming a deep-rooted clump. See Midwest native prairie grasses.
- Blue fescue (Festuca glauca): a small mound under about a foot tall, good for edges and containers.
- Autumn moor grass (Sesleria autumnalis): a compact clump, around 12 to 18 inches, with fine green to chartreuse blades.
- Blue grama ‘Blonde Ambition’ (Bouteloua gracilis): a clumping cultivar with horizontal seed heads. A designer in one competitor source recommends it as a non-reseeding substitute for Mexican feather grass.
- Switchgrass cultivars (Panicum virgatum, such as ‘Northwind’ or ‘Heavy Metal’): upright clumps. Some cultivars are said not to reseed aggressively, though seedling behavior can vary by site.
Tall options that still behave
Gardeners often ask about the tallest ornamental grass. Giant reed (Arundo donax) and giant miscanthus can reach 10 feet or more, but giant reed is invasive in many places and is not a good choice for a typical garden.
For height without the risk, look at switchgrass, big bluestem, Indian grass or upright cultivars of Miscanthus. Check seeding habits for Miscanthus, since some forms self-seed in certain regions, and sterile or well-behaved cultivars are available.
Shade-tolerant clumpers
- Japanese forest grass (Hakonechloa macra): arching, cascading mounds that slowly widen. See growing Japanese forest grass.
- Tufted hair grass (Deschampsia cespitosa): neat tufts that tolerate part shade.
- Northern sea oats (Chasmanthium latifolium): shade-tolerant, though it can self-seed in some gardens.
- Sedges (Carex): many are clump-formers, but a few spread by stolons, so check the specific cultivar. See grasses vs sedges.
Grasses to be careful with
Check local guidance before planting any of these:
- Running bamboo: spreads by rhizomes and can be very hard to remove once established. Clumping bamboos are a different matter; see running vs clumping bamboo.
- Mexican feather grass (Nassella tenuissima, also sold as Stipa tenuissima): beautiful but seeds heavily and is listed as a problem plant in California.
- Pampas grass (Cortaderia selloana): seeds readily in some regions. See is pampas grass invasive.
- Fountain grasses: some species and cultivars (notably Pennisetum setaceum) are flagged as invasive in warm regions, while sterile cultivars are safer.
- Giant reed, ribbon grass and some forms of Chinese silver grass: listed as invasive in various places.
- Blue lyme grass (Leymus arenarius): a running grass best kept for slopes and sandy sites, not formal borders.
Which ornamental grasses spread
The grasses that spread fall into two groups: rhizomatous or stoloniferous types that creep outward (giant reed, ribbon grass, blue lyme grass, some sedges) and seeders that reproduce by dropping seed (Mexican feather grass, pampas grass in certain regions, some fountain grasses). A third group, short-rhizome types such as switchgrass and Japanese forest grass, spreads slowly and can usually be controlled with a spade or edging.
Keeping clumps in check
Even a good clumper outgrows its spot eventually. When the center of the clump thins out, or the plant is too large for its space, dig it up in spring (or early fall for cool-season types) and split it with a sharp spade. Replant the healthy outer pieces and discard the dead center (more in how to divide and transplant ornamental grasses). Our guide to caring for ornamental grasses has step-by-step division advice.
To limit seeding, you can cut seed heads before they ripen, though that gives up winter interest. Seedlings are usually easy to pull when small.
Check local lists first
“Non-invasive” is regional. Before buying, check your state or provincial invasive plant list, or ask a local extension office or nursery. Nurseries can stock plants that are problematic nearby without realizing it. For a broader look at what is available once you have checked, see types of ornamental grasses.