The Best Way to Prune Ornamental Grasses
Ornamental grasses provide a low-maintenance option that many homeowners are wanting. Caring for ornamental grasses often requires nothing more than watering during establishment and enjoying the spectacular texture and form the rest of the year. By March, however, your ornamental grasses become far more messy than magnificent. Here’s what you need to know about pruning your ornamental grasses.
While it’s tempting to cut back your ornamental grasses in the fall, leaving the foliage during the winter months provides texture and form that may be lacking during that season. When February and March come around, however, they can look a bit tired of winter. This is the time – before they’ve begun sending up new growth – to cut back your ornamental grasses.
This list consists of ornamental grasses and sedges that are commonly planted in St. Louis landscapes.
How to Prune Ornamental Grasses
Maiden Grass (Miscanthus)
Fountain Grass (Pennisetum)
Switchgrass (Panicum)
Miscanthus sinensis ‘Gracillimus’ Photo Courtesy Monrovia 
Pennisetum alopecuroides ‘Hameln’ Photo Courtesy Monrovia 
Panicum virgatum ‘Northwinds’ Photo Courtesy Monrovia
These ornamental grasses will all go dormant during the winter. This means they will turn brown at the start of colder temperatures. They will send up new growth from the base of the plant every spring so, to maintain a clean appearance, they benefit by being trimmed back in February or March.
Cut the dry foliage to the ground but, to eliminate damage, stay above the crown of the plant. The plant crown is where the plant stem meets the roots. Typically you can leave around 3-4″ of stem for Fountain Grass and around 6″ for Maiden and Switchgrass. If you are uncertain where the crown is, it is always better to leave an extra couple of inches.
Lilyturf / Monkey Grass (Liriope)
Sedge (Carex)
Blue Fescue (Festuca)
Liriope muscari ‘Big Blue’ Photo Courtesy Monrovia 
Carex morrowii ‘Aurea-variegata’ Photo Courtesy Monrovia 
Festuca glauca ‘Elijah Blue’ Photo Courtesy Monrovia
These ornamental grasses are small and stay evergreen. This means that by the end of the growing season, they will still hold much of their color, but there will be brown foliage mixed in, leaving a somewhat messy appearance. To clean up your evergreen ornamental grasses, put on your garden gloves and run your fingers through the foliage. This is effective at pulling out the dead and unsightly foliage.
Occasionally your evergreen grasses need a more aggressive approach to rejuvenate them. At this point, you can trim them back with your pruners. This should be done early spring, with only two-thirds of the foliage removed. Within a few months after pruning, these ornamental grasses will look like new with their fresh foliage.
This rejuvenation pruning, however, causes the plant to lose energy that is stored in their leaves. Therefore, they should only receive an aggressive pruning every 2 to 3 years if necessary.
Japanese Forest Grass (Hakonechloa)
While still working at making the leap to a St. Louis garden staple, Japanese Forest Grass is not one to be forgotten. Though this dramatic foliaged grass is showy all season long, it takes on a burgundy tint in the fall and winter — a rarity for partial shade plants! Prune out the old foliage before the new leaves emerge in the spring to best maintain this ornamental grass.
Yucca (Yucca)
While technically not grass, the low-maintenance and minimal water that Yucca requires is making it a popular plant to grow in our St. Louis climate. Typically, Yuccas only need to be cleaned — this can be done by taking the old or damaged leaves and pruning them back to the crown. To completely rejuvenate an old or un-maintained Yucca, prune back to about 1 foot mid-spring. Be patient though, your Yucca will take around 4 months for it to grow out of the aggressive pruning.
Proper pruning of these architectural beauties will keep them looking magnificent from spring through winter.
