How to Grow Ornamental Grasses

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Knowing how to grow ornamental grasses comes down to three decisions: the growth habit, the planting season and the site. Clemson’s home garden factsheet calls ornamental grasses valued for their hardiness and ease of care, and it says most of them must have well-drained soil and full sun. The Colorado State and Iowa State pages agree on the basics but differ on sun hours and watering. This guide sets out what each source says, and where they disagree, it shows both figures.

Quick answer

• Sort the grass first. Clemson describes clumping and spreading habits, and it warns that spreading grasses “may overtake desirable plantings.”
• Plant warm-season grasses in spring and cool-season grasses in fall. Colorado State says container-grown grasses can go in all season, stopping a month before the first frost.
• Set the crown level with the soil, water thoroughly after planting, and give the first few weeks close attention.
• Let the plants stand through winter, cut back in early spring, and divide the clump every three to four years, or sooner when the center thins.

Sort the grass by habit and season

Clemson splits grasses into two habits. Spreading grasses “expand rapidly by aboveground or underground stems”, while clumping grasses form a clump that widens over time. Clemson also says care must be taken in planting spreading grasses, since they can overtake plantings nearby. The same factsheet notes that “Most ornamental grasses are perennials, living for two or more years.”

Season matters as much as habit. Clemson explains that “Cool season grasses begin new growth in fall or winter and bloom in spring or early summer”, while “Most ornamental grasses for the South are warm season growers.” Warm-season types “grow rapidly during spring and summer, bloom in late summer or fall, and are dormant through the winter.” Knowing which group a plant belongs to tells you when to plant it and when to divide it.

Height is the third sort. Clemson describes grasses that range from tall specimens down to low ground covers, and Iowa State adds that “While small in the nursery, many can get quite large in just a couple of years, so check the labels carefully for mature size and site preferences.” Choose by mature size, not by the pot.

Choose a site with the right light and drainage

Clemson’s rule is short: “Most ornamental grasses must have well-drained soil and full sun.” Colorado State is more specific about light, saying “Grasses generally grow best in three to five hours of direct sun each day.” These two general statements do not match, and Clemson does not put full sun into hours. Colorado State’s plant table does list some grasses as full sun, so check the entry for the grass you want before you choose a spot. Where you have a choice, pick the sunniest spot with good drainage.

Shade changes the result. Colorado State says that “In shade, these grasses may not bloom, are often lax and tend to fall over, and may not develop peak fall color.” Clemson notes that a few grasses tolerate shade, and it gives “northern sea oat grass, Japanese forest grass, and sedges” as examples. If your spot is shady, choose a shade-tolerant type rather than forcing a sun grass to fit.

Soil is less of a worry than drainage. Clemson states that “Ordinary garden soil is adequate for most grasses”, and it adds that “Some grass-like sedges and rushes will thrive in moist or even wet soil.” For a raised bed, the same page says “Planting them in raised beds will help to ensure good drainage.” To work out how much soil a raised bed holds before you fill it, see how much soil a raised bed garden needs, and for the filling step, see how to fill a raised bed.

Plant at the right time and set the crown level

Timing follows the season group. Clemson says that “While many perennials prefer fall planting in South Carolina, the warm season ornamental grasses will do best if planted in spring.” It adds that “Cool season grasses can be planted in fall.” Colorado State gives a longer planting window for container-grown plants, which “can be planted all season, stopping a month before the first frost.” The same page warns that “Late planting of grass divisions is not recommended, particularly for warm-season types.”

Most grasses arrive in containers. Clemson advises that “If plants are pot-bound, loosen the roots around the bottom and sides of the root ball.” Set the plant so the crown sits where the source says it should: the crown, “the point where roots and top join”, should be “even with the soil surface.” Spread the roots out, refill the hole, and firm the soil around them to avoid air pockets.

Spacing comes next. Clemson’s rule is to “Plant grasses as far apart as they will grow in height at maturity.” Iowa State’s warning about fast growth points the same way: check the mature size on the label before you set the plant. A grass that looks small in its pot can fill a bed within a couple of seasons, so give it room from the start.

Water well after planting, then ease off

Watering needs change over time. Clemson says “Water plants thoroughly after planting to settle the soil around the roots”, and it asks you to “Pay close attention to watering the first few weeks after planting.” Once established, Clemson states that “Most ornamental grasses will grow best with at least 1 inch of water per week from rain or irrigation”, and it notes that “Drip irrigation is an excellent way to water grasses.”

Iowa State takes a lighter line. Its page says that “Once established, grasses need minimal care requiring watering only in times of drought.” The two figures differ. Clemson gives a weekly amount, while Iowa State ties watering to drought. Colorado State adds a useful rule for native grasses: “Generally, among the natives, the taller the grass, the more water the plant requires.” Keep an eye on the rain in your area and adjust, rather than trusting one figure for every grass.

Feeding is a short job. Clemson says “Most ornamental grasses need very little fertilizer”, and Iowa State says “Ornamental grasses rarely need fertilizer.” Iowa State gives the one exception: “If growth is pale, weak, or floppy, scatter some granular fertilizer around them in the spring.” Clemson adds a caution that too much nitrogen can lead to overly vigorous growth and weak stems that fall over.

Leave the winter interest, then cut back in spring

Many grasses are worth keeping through winter. Iowa State says to “Let grasses and their ornamental flower heads stand all winter”, and adds that “Even when tan and dead, they are quite attractive after a snowfall.” Clemson agrees that “Since many grasses are attractive in the garden during winter,” cutting them back “is usually done in late winter or early spring.”

When you cut, the height is the choice. Clemson advises that you “Cut stems to a few inches above ground level for best appearance.” Iowa State gives the timing: “Cut back ornamental grasses in early spring before the new growth appears.” Colorado State adds a safety note: “Use hedge shears and wear gloves to prevent cuts from the razor-sharp edges of some species.”

Some evergreen grasses behave differently. Clemson says that “Some evergreen grasses, such as sedges” do not recover quickly from being cut back. For those, Clemson recommends that you “Comb the foliage of these plants with gloved hands in spring to remove old leaves.”

Divide clumps before the center thins

Dividing is the job most gardeners put off. Clemson says that “Most grasses should be divided every 3 to 4 years”, and warns that “If ornamental grasses are not divided, they will eventually become thin or die out in the center.” Iowa State gives a visual cue: “If the center of the clump begins to thin or die out, divide in early spring just as the new growth appears.”

Do it while the clump is still manageable. Clemson advises that “It is best to divide grasses while they are a manageable size”, because “Overgrown grasses can be incredibly difficult to dig and divide.” Colorado State makes the same point from a different angle: “A number of perennial grasses form root masses that can be very difficult to divide and transplant.”

The timing depends on the season group. Clemson says to “Dig and divide warm season grasses during early spring, just before new growth starts”, and to “Divide cool-season grasses in early fall.” Iowa State’s early spring advice fits the warm-season step, so check the type before you pick the season for a cool-season grass.

The process is physical. Clemson notes that “Most grasses have tough, vigorous root systems and may have to be divided with a shovel, saw, or ax.” Its method is to “Hose off soil to make the roots easier to work with, then separate and replant the vigorous growth on the outer edges of the clump.” Finish by replanting quickly, since Clemson says to “Replant promptly and never let the roots dry out.”

Keep spreading grasses in check

Spreaders need a plan from day one. Clemson’s method is to “confine the root system in a deep bottomless container” to stop running grasses from taking over. Clemson also warns that “Non-native grasses that seed vigorously should be used with care, especially near natural or wetland areas.”

Seed spread is a separate concern. Clemson says that “Fountain grass reseeds and may be invasive into natural areas.” By contrast, switchgrass “reseeds occasionally, but is not invasive”, according to the same page. The difference matters when you choose a type, because the seed habit is the part that travels beyond your bed.

Mistakes to avoid

• Planting for the pot size. Iowa State warns that many grasses get large within a couple of years, so check the mature size first.
• Setting the crown off level. Clemson says the crown should be even with the soil surface.
• Putting a spreader where it can run. Clemson recommends a deep bottomless container to confine running roots.
• Dividing an overgrown clump. Clemson says overgrown grasses can be incredibly difficult to dig and divide.
• Planting divisions late in the season. Colorado State says late planting of divisions is not recommended, especially for warm-season types.
• Using a sun grass in deep shade. Colorado State says that in shade these grasses may not bloom, and that they tend to fall over.

How we chose

We limited this guide to three extension pages that we opened with curl on 2026-10-22: a Clemson Extension home garden factsheet on ornamental grasses and grass-like plants, a Colorado State Extension page on ornamental grasses, and an Iowa State Extension page on caring for ornamental grasses. Each one returned HTTP 200. A Missouri Extension publication returned HTTP 403 and was not used. We kept only the steps that at least one page states in its own words, and each quoted sentence was checked against the text we pulled. We did not recommend any product or named cultivar.

What we could not verify

The three pages describe ornamental grasses in general terms. Clemson’s factsheet names many cultivars with hardiness zones and heights, but it does not give a planting spacing in inches for each one. The pages also disagree on a few points, and this guide shows the difference instead of picking a side.

What the sources do not say

• Sun needs disagree. Clemson says full sun, while Colorado State gives three to five hours of direct sun each day. Neither page links the two.
• Watering needs disagree. Clemson gives at least 1 inch of water per week, and Iowa State says watering is needed only in times of drought once plants are established.
• No page gives a single division date that works for every grass. Clemson splits warm and cool types, and Iowa State gives early spring for clumps in general.
• Clemson says fertilizer should follow a soil result rather than a fixed schedule, but none of the pages gives a rate or a month beyond the spring step.
• None of the pages gives a spacing figure in inches or centimeters for any named grass.

Frequently asked questions

Can ornamental grasses go in a raised bed?

Yes. Clemson says that planting them in raised beds helps ensure good drainage, and it notes that ordinary garden soil is adequate for most grasses. Plan the bed with the mature size in mind, because the page does not give a spacing figure.

Do ornamental grasses need fertilizer every year?

Usually not. Clemson and Iowa State both say most grasses need very little, and Iowa State suggests a granular feed in spring only when growth looks pale, weak or floppy.

When is the best time to divide an ornamental grass?

It depends on the type. Clemson says to divide warm-season grasses in early spring, just before new growth starts, and cool-season grasses in early fall. Iowa State says to divide clumps in early spring as new growth appears.

Should ornamental grasses be cut back in the fall?

Iowa State recommends leaving them standing through winter for their look and cutting back in early spring. Clemson also favors late winter or early spring for cutting back, since the grasses are attractive through the cold months.

Are all ornamental grasses invasive?

No. Clemson says a few grasses, especially running or prolific seeders, can become pests in the wrong place, and it names fountain grass as one that reseeds and may be invasive. Switchgrass, by the same page’s account, is not invasive, so check the species before you plant.

Sources

• https://hgic.clemson.edu/factsheet/ornamental-grasses-and-grass-like-plants/ (opened 2026-10-22)
• https://extension.colostate.edu/resource/ornamental-grasses/ (opened 2026-10-22)
• https://yardandgarden.extension.iastate.edu/faq/how-do-i-care-ornamental-grasses (opened 2026-10-22)