The short answer
Ornamental grasses are low-maintenance. Give them enough sun, well-drained soil and regular water in their first year. After that, most need little more than an annual cut-back and occasional division. Skip the fertilizer in most cases.
Planting
When: Spring or early fall is best. Planting before summer heat gives roots time to settle. If you plant in fall, aim for at least 6 to 8 weeks before the first expected frost. Warm-season grasses can also go in around late spring and early summer.
Where: Most ornamental grasses prefer full sun, meaning around 6 hours or more a day. Some tolerate part shade, such as Japanese forest grass and many sedges. In too much shade, sun-lovers tend to flop and flower less.
Soil: Good drainage matters more than richness. Most grasses grow well in average, poor, sandy or clay soils as long as the water does not sit around the crown. In heavy soil, mixing in compost at planting can help, and some grasses handle clay better than others.
Depth: Set the plant so the crown (where the roots meet the stems) is level with the soil surface. Some grasses, notably Pennisetum, are sensitive to being planted too deep, and the crown can rot.
Spacing: Check the plant tag for the mature spread and leave room for it. Our spacing guide gives distances by size. Crowded plants may need dividing sooner.
Watering
Water new plants regularly through their first growing season to help roots establish. A common guideline is a deep soak once or twice a week in dry weather, adjusted for soil and climate.
Once established, many grasses are drought tolerant, but it depends on the type:
- Native prairie grasses such as switchgrass and little bluestem generally cope with dry spells well.
- Pennisetum prefers average moisture and may show brown leaf tips if the soil dries out too much.
- Miscanthus appreciates a bit more moisture than many other grasses.
- Moisture lovers such as Cyperus (a sedge) and some rushes like frequent watering.
A layer of mulch in the first year helps hold moisture. Keep it from piling against the crown, because constant moisture there can cause rot.
Fertilizer and soil
Most ornamental grasses do not need feeding. Rich soil and extra nitrogen tend to produce tall, soft growth that flops over. This is especially true of tall grasses. Do not use lawn fertilizer on them. If your soil is very poor, a light top-dressing of compost or a shredded-leaf mulch in fall is usually enough. See should you fertilize ornamental grasses.
Cutting back
Cutting back is the main yearly task.
- Warm-season grasses: cut to a few inches above the ground in late winter or early spring, before new growth.
- Cool-season grasses: cut in very early spring, leaving about a third of the foliage.
- Evergreen grasses and sedges: comb out dead blades instead of cutting hard.
Details, tools and mistakes to avoid are in should all ornamental grasses be cut back in the spring.
Dividing
Dividing keeps clumps healthy and gives you free plants. Divide when the center of the clump dies out or the plant outgrows its space, often every few years.
- Warm-season grasses: divide from late spring to midsummer, when they are actively growing.
- Cool-season grasses: divide in early spring or early fall. Spring is usually the safer choice.
- Evergreen grasses and sedges: divide in spring.
Do not divide while the plant is flowering or dormant. (Our full guide to dividing and transplanting grasses goes further.) To divide:
- Dig up the clump, or cut it in sections with a sharp spade.
- Pull or cut it into pieces, making sure each has healthy roots.
- Discard the dead center and replant the outer growth at the same depth.
- Water well and keep the divisions moist until they establish.
Large, tough clumps can be hard work. Some gardeners cut the grass down first and then cut the clump into wedges. Wear gloves, since leaf edges can cut.
A simple yearly calendar
- Late winter / early spring: cut back or comb out old foliage. Divide cool-season grasses if needed.
- Spring: plant new grasses. Water as needed.
- Summer: water new plantings. Divide warm-season grasses if needed.
- Fall: enjoy plumes and color. Plant cool-season grasses early in the season. Mulch lightly with shredded leaves if you like.
- Winter: leave seed heads and foliage standing for interest and wildlife.
Common problems
- Floppy growth: usually too much shade, water or fertilizer. See why ornamental grasses flop over.
- Dead center: a sign the clump needs dividing.
- Brown tips: often dry soil, especially on Pennisetum.
- Plant not coming back in spring: check that the crown was not planted too deep or kept wet over winter.
Understanding whether your grass is cool-season or warm-season makes all of this easier. See warm-season vs cool-season ornamental grasses and our guide to types of ornamental grasses.