What zones 3 and 4 mean for grasses
Zone 3 has average coldest winter temperatures of about -40°F to -30°F, and zone 4 about -30°F to -20°F. At those temperatures, the choice of plant matters more than anything else. The good news is that many North American prairie grasses evolved with cold, snowy winters and are among the toughest options.
If your zone is milder, our pillar guide to hardy grasses for zones 5 and 6 covers more choices.
Best tall grasses
- ‘Karl Foerster’ feather reed grass (Calamagrostis × acutiflora): a narrow, upright cool-season grass, about 4 to 5 feet tall, with wheat-colored plumes in early summer that hold up into winter. It is widely listed as hardy to zone 3 or 4.
- Switchgrass (Panicum virgatum): a native warm-season grass that ranges from about 3 to 6 feet depending on the cultivar. ‘Northwind’ is known for a stiff, upright habit, and ‘Shenandoah’ for red fall color. Hardiness listings run from zone 3 or 4, so check the tag for the cultivar you buy.
- Big bluestem (Andropogon gerardii): a tall prairie native, with cultivars such as ‘Blue Steel’ and ‘Blackhawks’ offering bluish or purple-red tones. It does best in a sunny, open spot.
- Indian grass (Sorghastrum nutans): golden fall color and bronze-gold plumes. The ‘Golden Sunset’ selection was developed for northern climates and is listed as zone 3 hardy.
Mid-size and short grasses
- Prairie dropseed (Sporobolus heterolepis): a fine, arching mound about 2 to 3 feet tall and wide, with fragrant late-summer flowers and copper-orange fall color. It grows slowly, so patience helps.
- Little bluestem (Schizachyrium scoparium): blue-green summer foliage that turns copper, orange and red in fall. It tolerates lean, dry soil. Compare cultivars in little bluestem varieties.
- Blue grama (Bouteloua gracilis, including ‘Blonde Ambition’): a low, fine-textured native with unusual eyelash-shaped seed heads. Suited to dry, sunny, poor soil.
- Blue oat grass (Helictotrichon sempervirens) and blue fescue (‘Boulder Blue’, ‘Elijah Blue’): cool, silvery-blue foliage for borders and edges. Both need good drainage, and blue fescue is often a short-lived perennial (see why blue fescue dies in the center). Some sources rate them for zone 4.
- Overdam feather reed grass: a variegated green-and-white form, usually listed for zones 4 to 9.
Shade options
Grasses for shade are fewer in the far north. Pennsylvania sedge (Carex pensylvanica) is a native, semi-evergreen sedge that makes a soft, lawn-like carpet in shade, and is often listed to zone 3. Northern sea oats (Chasmanthium latifolium) tolerates light shade but is usually rated for zone 4 or 5 and up, so it is a marginal choice at the cold end. Tufted hair grass (Deschampsia cespitosa) handles sun to part shade and is cold hardy.
Grasses that are not hardy enough
A few popular grasses are not reliable in zones 3 and 4:
- Pampas grass (Cortaderia selloana) is a plant for warmer climates and will not survive zone 3 winters.
- Pink muhly grass (Muhlenbergia capillaris) is generally listed for zones 5 or 6 and up, so it is a poor bet in zone 3. A related muhly, ‘Undaunted’, is sometimes advertised as hardier, so check the plant tag for the exact rating.
- Purple fountain grass (Pennisetum setaceum) is an annual in cold climates.
- Perennial fountain grass (Pennisetum alopecuroides) is typically hardy to about zone 5. Some compact cultivars, such as ‘Cassian’ (a dwarf fountain grass that stays roughly 2 to 3 feet tall in bloom), are listed to zone 5 or 6, so they would be a gamble or a container plant in zone 4. Our guide to overwintering ornamental grasses covers bringing potted grasses through the cold.
When a nursery lists a rating one zone lower than most other sources, treat it as marginal and plant in a sheltered spot with good drainage.
Where to plant, and how late you can plant
Most of the grasses above want full sun and well-drained soil. A spot with some wind shelter can help the less hardy ones, and snow cover acts as insulation.
Spring is the best planting time in zones 3 and 4. You can also plant in late summer or early fall, but roots need weeks to settle before the ground freezes. A common guideline is to finish planting about six weeks before the ground freezes; if you plant later, water well, mulch, and expect a higher risk of loss. Warm-season grasses such as switchgrass and bluestem are usually safer planted in spring or early summer, so they have a full season of roots.
Winter care
Do not cut your ornamental grasses back in fall. The standing foliage helps protect the crown from the worst cold, catches insulating snow and looks good against it. Cut grasses back to a few inches above the ground in early spring, before new green growth emerges (more in cutting back ornamental grasses). Dividing crowded clumps in spring keeps them vigorous.
Perennial or annual? How to tell
A perennial grass returns each year from the same roots; an annual completes its life in one season and must be replanted. The plant tag or listing will say, and hardiness zone is the clue: if the grass is rated at least as cold-hardy as your zone, it should behave as a perennial. If not, as with purple fountain grass, it will be an annual in your garden.
Looking at seeds instead of plants? Our guide on where to find ornamental grass seeds lists what to look for. For prairie-style plantings in the Upper Midwest, see Midwest and native prairie grasses.