Activity: Cutting back ornamental grasses in late winter

Why: To ensure proper growth of ornamental grasses, you will need to cut them back each year before new growth emerges. If you wait too long, the grasses likely will delay new growth by up to three weeks. This occurs because old leaf blades keep the crowns from warming up properly. Also, new growth can begin to grow into old blades, making it impossible not to cut back both.

How: 1. Choose a sunny day so you can see any new growth coming out of the ornamental grass and to make sure it is dry. Locate any grassy, green growth coming out of the ornamental grass clump.

2. Wrap tape or tie twine around the circumference of the grass. Any wide tape will do, as long as it’s sticky enough to keep a hold on the grass blades. A strong masking tape is preferable if you plan to compost the grass. Depending on the width and height of the ornamental grass, you might need to wrap tape or tie off with twine in 2-3 positions along the height of the grass and possibly divide the grass blades into 2-3 bundles.

3. Now that your ornamental grasses are bundled neatly, take your shears and prune the grass. You can lean the ornamental grass bundle away from you as you cut. If your ornamental grass is well established, you may prefer to use a power hedge trimmer. Either way, prebundling the grass will make it easier than grabbing handfuls of grass blades and hand pruning.

Cut all dead blades on the ornamental grass clump as low as 4-6 inches from the ground. Don’t worry if it looks unkempt with just the green leaves showing, as the clump of grass will put out new shoots and fill in within a few weeks. If no new shoots are showing, then cut evenly 4 inches above the ground.

When: The best time to cut back your ornamental grasses is right before the new season’s growth begins. In most regions, this is late winter or early spring. Many ornamental grasses are attractive through winter, while others might not show as well. If your ornamental grasses don’t remain attractive during winter, you can cut them back in late fall.

Some ornamental grasses are evergreen and won’t tolerate cutting back well. If you have evergreen ornamental grasses, don’t cut them back; instead, simply remove the old leaves or blades in early spring.

What’s needed: Gloves and long-sleeved shirt for protection from sharp grass blades and dry debris. Sharp garden shears, pruning shears or power shears. Sturdy tape, twine or bungee cords to bundle the grasses into sheaves.

For further information on ornamental grasses adapted to the Rocky Mountain region, and design and care, go to ext.colostate.edu and select CSU Extension Gardening Series Fact Sheet No. 7.232 Ornamental Grasses.

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When you have questions, CSU has research-based answers. Get answers to you horticultural questions by calling the Master Gardener Volunteer Help Desk at 520-7684 or emailing CSUmg2@elpasoco.com. Note: Volunteers are “on call” during our winter hours. Please allow 7-10 days for a response.