Jennifer Schultz Nelson
Extension Educator, Horticulture
Some of the first plants I purchased when we bought our home a few years ago were ornamental grasses. They are going into their fifth growing season and are going strong without much extra care.
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.
I probably should have divided my zebra grass, Miscanthus sinensis 'Zebrinus' last year. After about its third growing season, the center of the clump died out, which is very common for Miscanthus. Quite frankly, I have been dreading the job. Many ornamental grasses have extensive, strong root systems which make them very drought tolerant, but a pain to dig up and divide. My husband went to a class last year on ornamental grass and the speaker showed the two shovels she had broken trying to dig up plants to give away during her class! Hearing about this didn't make motivate me to divide our grass.
I've been trying to find a less tool-threatening method to use in renovating my Miscanthus, figuring I'd have to dig up the whole clump, split it and replant a single clump and find homes for the rest. Not only would that be a lot of back breaking work, it would take my nice big clump of grass and reduce it to a much smaller size, something I really don't want.
A Master Gardener came to me with an interesting idea. She had heard that you could renovate an ornamental grass with a dead center without digging it up. I was all ears! Whatever show she was watching recommended using a sawzall to remove the dead center, filling the spot with compost or rich soil. The grass should fill in the empty center. As an added bonus, since it involves power tools, chances are my husband will jump at the chance to do this chore!
I did some research and found mention of cutting out the dead center of ornamental grasses in some of my horticulture references, so I don't think the method is as crazy as it may sound.
Before you cut the dead centers out of your ornamental grasses this 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 people, myself included, 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 for homeowners that call our office each year. Some sources tell people to cut back grasses in late winter, some say early spring. Many people call me demanding to know "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 your trusty sawzall 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.
Some sources advocate burning the dead stubble of ornamental grass before new growth begins in the spring. While this will remove all traces of last year's old growth, burning lawn waste may not be allowed in your town (it is prohibited in Decatur). Besides that, burning the stubble is a potential safety hazard. At a program a few years ago, someone told me about "a friend" of theirs burning old growth on ornamental grass and accidentally catching the neighbor's cat on fire! If you do choose to try this method, please be careful and don't hurt yourself or the local animals!
Keep in mind this spring 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 ask me 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 I would consider 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, I encourage you to give them a second look.