Pruning Ornamental Grasses: How to Groom and Control

  • 01 of 10

    Grasses Gone Wild: Tame Those Ornamentals

    fountain grass
    Native landscaping with fountain grass. Justus de Cuveland/Getty Images

    Ornamental grasses are fairly new to the landscape scene—they've increased in popularity in the past decade or so. In regions experiencing drought, ornamental and native grasses indigenous to the area have become a smart and stunning part of the landscape. Some grasses have been brought from parts of the world that share similar climates, but even landscape professionals aren't completely sure how to handle all of these exotic imports.

    Unlike rose bushes or boxwood hedges, there's not really a standard method for pruning or grooming ornamental grasses. And not every landscaper or gardening expert knows how to take care of everything in the garden, including these grasses that can grow quite large—as in tall and wide. Follow these steps to groom your grasses and get them to looking great. In some regions, that means they have the potential to be beautiful accent plants nearly year 'round.

    Most ornamentals are easy to grow, requiring little water and fertilizer and no pesticides. They look equally beautiful planted poolside—blowing in the breeze, in containers on patios, and as accent plants in other areas of the landscape.

    See How the Other Grasses Grow

    Check out your neighborhood or cruise nearby areas where similar-looking ornamental grasses grow. Take pictures of grasses that are beautiful and thriving. Parks, botanical gardens, and public places like hotels or nice restaurants often use gardeners and landscapers who treat pruning as an art form, and really know how to cut and groom sedges and flaxes. Observe up close, if possible.

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  • 02 of 10

    Pennisetum Setaceum: A Grass for All Seasons

    pennisetum setaceum rubrum picture
    Regular grooming keeps fountain grass handsome throughout the year. Lisa Hallett Taylor

    Pennisetum setaceum 'Rubrum', commonly known as fountain grass or purple fountain grass, has been increasingly popular as both an accent plant and focal point in many landscape designs. Although Pennisetum setaceum's growing seasons are summer and fall, in some parts of the western United States where temperatures remain above 20 degrees, it can bloom and be a mainstay in the garden through the winter.

    Most care instructions advise to cut it down to a few inches above ground in late winter to early spring and to divide clumps when the grass's growth begins to weaken. In mild climates, moderate, frost-free temperatures allow fountain grass to grow throughout the year, periodic grooming can turn your Pennisetum into a perennial.

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  • 03 of 10

    Sizing Up a Shaggy Mess

    grass cutting tools
    Garden tools and supplies for pruning ornamental grasses. Lisa Hallett Taylor

    Think this particular fountain grass looks unkempt? Maybe it's a candidate for an upcoming Grasses Gone Wild gallery. So what's wrong with this example? Having gone without a "haircut" since October, this particular fountain grass has gotten unruly. A rainy winter made everything in the garden grow, and ornamental grasses are no exception. Time to get down to business.

    Grass-Grooming Tools

    Like any project, gather your tools and stuff before you get down to business. What you'll need:​

    • Hand pruners
    • Hedge shears (electric of handheld, although the latter gives you more control)
    • Bow saw
    • Trowel
    • Gardener's gloves
    • Long sleeves or Armadillos—sleeves made of heavy-duty canvas over duck canvas to protect arms
    • Sturdy shoes —not sandals or high heels
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  • 04 of 10

    Don Your Gloves and Long Sleeves

    cutting pennisetum setaceum rubrum
    Long sleeves, gloves with cuffs protect you from itchy, prickly grasses. Lisa Hallett Taylor

    All types of grasses can make you itchy and some can scratch and cut, so it's a wise idea to wear something with long sleeves and a pair of jeans. Also wear gardening gloves—you'll quickly learn why. If you are going to be pruning several grasses, you might want to consider wearing Armadillos, which are sleeves made of duck canvas. Otherwise—ouch!

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  • 05 of 10

    Tie Up Grass

    tie grass with bungee
    Tie the grass together with a string, a rope, or bungee. Lisa Hallett Taylor

    Start by gathering the grass together with your gloved hands and securing it with string, rope, or a bungee. This makes it much easier to cut it all at one time and get it more even. Adjust the rope or cord higher or lower, depending on where you want to cut the grass. Some gardeners prefer to cut the grass below the rope, because the cuttings are easier to dispose of or put in the compost bin.

    Cutting and grooming ornamental grass makes it healthier. By removing all that dry, old growth that is basically a big mess of dead grass, new growth will actually be exposed to sunlight and fresh air. While it might be tempting to mow-down a mess like this, removal of the dry stuff and a good shaping is all that will be needed. If you are compelled to cut ornamental grass very short, do not trim it any lower than 4 inches from the ground.

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  • 06 of 10

    Combing Through the Grass

    picture of pennisetum setaceum rubrum
    Dig in and comb through the grass to clean out the dried canes. Lisa Hallett Taylor

    Tap into your inner hairstylist as you lean over the fountain grass and comb or rake your gloved fingers through the middle of the clump, grabbing all loose and dead or dried-up hairs (blades/branches). Comb through the entire grass, and shake it occasionally to get out more dried plant material. You may end up with a good-sized pile of the dead stuff, which you should pitch into a portable container as you go along. Otherwise, it's a real chore to clean up all of those blades and clumps of grass after you've done the pruning and grooming.

    So far, so good.

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  • 07 of 10


    picture of pennisetum setaceum fountain grass
    To thin-out grass, grab a small amount and cut down toward base. Lisa Hallett Taylor
    Grab a bunch of grass blades in one hand, pull them out to the side, and cut with a pair of hand pruners. Repeat throughout. Gather dead or dry-looking canes in your hand and cut down toward the base. To thin-out the grass, grab small sections in the middle and cut down toward the base, at different heights. Once it starts blooming (which will be in the coming weeks, depending on where you live), the grass will have a more natural, rounder shape with arching, fountainlike branches. Hence, the name, fountain grass.
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  • 08 of 10

    Divide Clumps

    mexican feather grass
    Mexican feather grass gets divided to preserve its billowy effect. Lisa Hallett Taylor

    After a few years, ornamental grasses will need to be divided at their base. How can you tell? The grass clump will be overgrown, possibly encroaching on neighboring plants or creeping out beyond the border or edge. In some cases, the centers of the grass clumps will have died out and need to be removed. Some, like this Mexican feather grass (Nassella tenuissima), are simple—just use a trowel to dig up a portion of the grass, roots and all. You can then divide the clump again, and replant them, although Mexican feather grass can be an aggressive re-seeder. In some regions, Nassella tenuissima is considered invasive and is classified as a weed. Under control in a contained, fenced yard, it is less likely to be a threat to the local landscape.

    For larger clumps that might have deeper roots, use a spade and some muscle to divide. Depending on the type of grass, you can either replant (and trim to about 4 inches above where it will be placed in the ground), or put it in your composting bin. What? You don't have a composting bin? Start one today.

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  • 09 of 10

    Don't Do This

    how to prune ornamental grass
    This dry little clump is fountain grass that's been cut way back to almost nothing. Lisa Hallett Taylor

    Many uninformed or "innocent" gardeners hack back ornamental grasses like Pennisetum setaceum. While that works well with some of the grasses, others just need some dead-heading and light pruning and shaping anytime you think about it. Ornamental grasses are pretty forgiving.

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  • 10 of 10

    The Grasses are in Bloom Once Again

    picture of ornamental grasses purple and lime green
    Purple and lime green make a striking color combination in the garden. Lisa Hallett Taylor

    Groomed and pruned carefully and not chopped down to obscurity, this fountain grass is starting to bloom, and beginning to sprout its showy and graceful dark-red/purple feather-like flowers. The lighter-green oat grass is also in bloom after a quick trim, and provides a striking contrast to the darker purple fountain grass. Nice, healthy and how it's supposed to look— ornamental.