Plant Palette

Plant Palette

Ornamental Grasses

Photo of Jennifer Schultz Nelson

Jennifer Schultz Nelson
Extension Educator, Horticulture
jaschult@illinois.edu

When choosing ornamental grasses for your home landscape, it will save you time and frustration to know a little about the two basic growth habits of grasses. Incidentally, these growth habits apply to grasses used for turf as well.

Grasses will tend to grow in two ways-- as clumps that get thicker and wider, or as a spreading mass which sends out rhizomes or stolons to colonize any available ground.

Clumping type grasses, such as Miscanthus, are welcome occupants of a perennial border, because they are polite and stay in the place you put them.

Spreading type grasses, such as Northern Sea Oats, Chasmanthium latifolium are rude guests in the perennial garden. They spread quickly via rhizomes and seed. Left unchecked, in a season or two they would crowd out everything around them. This trait can be used to your advantage if you are trying to reduce erosion on a hillside for instance. Rhizomes in a spreading grass will interlace and physically hold the soil in place.

Some ornamental grasses, such as Northern Sea Oats, produce viable seed, but many do not. A little research will tell you if a grass produces viable seed. If you find a particular grass produces viable seed that you do not want sprouting in your garden, you can still enjoy that grass in your garden-- just remove those seed heads by the end of the growing season. I love the look of the seed heads on Northern Sea Oats, but don't want it all over my garden. I remove the seed heads at the end of the growing season, which saves me the work of pulling thousands of seedlings the following spring.

It is fairly common for the center of some clump-type grasses to die; this is very common for Miscanthus. Dividing the parts remaining seems like an easy fix, but many ornamental grasses have extensive, strong root systems which make them very drought tolerant, but difficult to dig up and divide.

It is possible to use a handsaw, or a handheld electric saw to remove the dead center, filling the spot with compost or rich soil. The grass should fill in the empty center.

Before you cut the dead centers out of your ornamental grasses in the spring, most of the time you will need to cut back last year's old growth. While you could remove the year's growth at the end of the growing season, the reason a lot of many people enjoy ornamental grasses is that the tall stems and seed heads provide some winter interest in the garden.

Cutting back ornamental grass is a source of confusion. Some sources tell people to cut back grasses in late winter, some say early spring; you may wonder, "Which is it?" The answer is: as long as you cut it back before the new growth begins, you're just fine.

Before cutting back old growth on ornamental grass, tie the old stems together with twine or bungee cords. Use your pruning shears, hedge clippers, or an electric saw to cut the old growth a minimum of six inches up from the ground. You can then remove the old growth in one big bundle without stems falling everywhere. The stubble that remains will be quickly hidden by that year's new growth.

Keep in mind that not all ornamental grasses are hardy for our Zone 5b climate. Many are treated as annuals in this area. You can either let these plants die at the end of the season, or bring them in and attempt to overwinter them in your home or garage. I love using these annual grasses in containers to add height instead of the often overused Dracaena spike.

People always for plants to use in a "no maintenance" landscape. Unfortunately, this doesn't exist. Plants are living things, and need attention at some point. Ornamental grasses are what considered very "low maintenance". Besides a yearly haircut and occasional renovation or division, they typically need little extra care.

People seem to either love or hate ornamental grasses. "Too weedy looking" is the reason those that hate ornamental grasses give. The many different species of ornamental grasses available today challenges this response. If you have been hesitant to try ornamental grasses, consider giving them a second look.

Some grasses often considered invasive in the perennial garden:

Some grasses that behave themselves in the perennial garden:

Blue Lymegrass (Elymus arenarius glauca)

Perennial

Blue Fescue (Festuca species)

Perennial

Switchgrass (Panicum virgatum)

Perennial

Feather Reed Grass (Calamagrostis acutiflora)

Perennial

Ribbon Grass (Phalaris arundinacea)

Perennial

Purple Moor Grass (Molinia litorialis)

Perennial

Northern Sea Oats (Chasmanthium latifolium)

Perennial

Prairie Dropseed (Sporobolus heterolepis)

Perennial

Big Bluestem (Andropogon gerardii)

Perennial

Perennial Fountain Grass (Pennisetum alopecuroides)

Perennial

Little Bluestem (Andropogon scoparius)

Perennial

Annual Red Fountain Grass (Pennisetum setaceum)

Annual

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