Your retired ornamental grass needs a haircut, but when should you schedule its bob? The best time to cut back ornamental grass is spring, before new growth begins and after the last frost.
Whether your grass is warm-season, cool-season, or evergreen will determine when in spring you should trim (early-, mid-, or late-spring) and how much foliage you’ll need to remove. Growing evergreen grass? Put down the shears and lightly comb instead.
While some gardening guides suggest cutting warm-season ornamental grass in fall, Matthew McKernan, horticulture agent at K-State Research and Extension in Sedgwick County, says there are many reasons to wait until spring. There is one exception: “In areas where high fire danger is a concern, cutting back ornamental grasses in the fall may be beneficial in order to reduce wildfire fuel near the house or other structures.”
Types of ornamental grasses
The best time to cut back ornamental grass depends on whether it’s a warm-season, cool-season, or evergreen grass.
- Warm-season ornamental grasses love the hot weather of the Southern states. They’ll start growing in mid-spring to early summer once temperatures exceed 75 degrees Fahrenheit, and they go dormant in fall.
- Cool-season ornamental grasses thrive in spring and when temperatures are between 60 and 75 degrees Fahrenheit. They typically don’t die back in summer; however, their growth will slow considerably. These grasses are great for Northern homes where temperatures remain cool.
- Evergreen ornamental grasses maintain foliage all year round. These grass-like plants, such as sedges and rushes, are not true grasses.
The classification of these three grass types can sometimes be confusing. For example, warm-season and cool-season ornamental grasses may exhibit evergreen behavior in particularly suitable climates. However, in this article, we classify grasses based on their active growing season and reserve the term evergreen for consistently winter-green, grass-like species such as sedges and rushes.
Examples of cool-season ornamental grasses include blue fescue, blue oat grass, feather reed grass, and tufted hair grass. Warm-season ornamental grasses include little bluestem, maiden grass, and switchgrass.
Keep in mind that not all ornamental grasses are ideal for the landscape. For example, pampas grass is invasive, and so are some types of fountain grass.
When to cut back warm-season ornamental grass
Cut back your warm-season ornamental grass in mid- to late-spring before new growth begins and after the last frost.
If you live in an area prone to wildfires, remove dead ornamental grass in the fall to ensure a fire-resistant landscape.
You may be tempted to cut your warm-season ornamental grass in fall if you prefer the look of tidy winter garden beds. However, McKernan says waiting to cut your ornamental grass until spring has its benefits:
- Winter beauty: “Many ornamental grasses can provide a great fall color to the landscape, adding pops of red, orange, burgundy, and purple to the landscape,” he says. “Over the winter months, ornamental grasses and their seed heads provide a great deal of color, sound, and movement to the winter landscape.”
- Shelter for wildlife: McKernan adds, “Grasses and seedhead stems can also provide habitat for beneficial insects, pollinators, birds, and other wildlife.”
- Protect the plant from winter injury: “Leaving the foliage provides additional insulation for the plant near the ground level, where the crown of the plant sits,” McKernan adds. “Leaving the ornamental grasses untrimmed also helps the plant in the early winter and spring months too. Without the insulation of the foliage, the sunlight on warm winter days may encourage plants to attempt to grow prior to the start of spring, and suffer additional freeze or frost damage to new growth.”
How much should you cut back? Trim your warm-season ornamental grasses down to the ground. As a helpful rule of thumb, cut down to 3 inches above ground level for grasses growing 3 feet tall or under. Cut down to 6 inches above ground level for grasses growing above 3 feet tall.
When to cut back cool-season ornamental grass
Cut your cool-season ornamental grass in late-winter or early-spring before new growth begins and there’s no threat of frost. If you cut before the last frost, winter injury may harm new growth. The further north you live, the longer you can expect to wait for the last frost to pass in your area.
Unlike warm-season ornamental grass, which you can cut down near the ground, cool-season ornamental grass can’t handle such a severe trim. Instead, remove two-thirds of the plant and keep one-third.
When to cut back evergreen ornamental grass
Evergreen ornamental grasses, like sedges and rushes, don’t require a heavy-duty trim. Instead, selectively prune dry foliage and old flowers in late-winter or early-spring. This can be as simple as running your gloved hand through the plant and combing out the dead material.
FAQ about when to cut ornamental grass
If you cut the ornamental grass too late in spring, you risk accidentally cutting new growth. This may lead to an untidy appearance for a short while until new growth sets in.
Pay attention to when your ornamental grass grows the most. If it grows most in the summer, then it’s a warm-season grass. If it slows down in summer but is rapid in spring and fall, then it’s a cool-season grass. Evergreen sedges and rushes thrive all year round and don’t enter dormancy.
If your ornamental grass is already sprouting new growth, then you’ve missed the optimal trimming window.
• The Best Ornamental Grasses for Wisconsin
• Native Ornamental Grasses for South Carolina Landscapes
• South Dakota Native Grasses for Lawns and Landscapes
Hire a pro to care for your landscape
Spring is a busy time for your yard. Not only does your ornamental grass need a trip to the salon, but your turfgrass, soil, and garden beds also need a spa day.
And so do you. Hire a lawn care pro through Lawn Love to mow, fertilize, and remove weeds so you can enjoy a well-deserved break.
Main Image: Cutting back clump of ornamental grass. Image Credit: maryviolet / Adobe Stock
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