Ornamental Grasses Add Grace and Movement

Barb Mrgich
Adams County Master Gardener

(10/3) Garden designers often refer to movement as an element to consider when planning your garden. Plants are stationary. So how do you get movement? An easy answer is ornamental grasses. Picture a fall breeze rustling across a group of ornamental grasses causing them to wave gracefully suggesting flowing water. The result can be very beautiful.

If you have a steep bank, grasses are a great solution to end dangerous mowing situations while, at the same time, preventing erosion. Grasses, especially native grasses such as Switchgrass, Prairie Drop Seed, Little Blue Stem and Indian Grass, have deep, fibrous roots (as deep as five feet) to hold the soil in place. They will come up by themselves every year and, unlike turf grass, you don’t have to mow them every week.

Ornamental grasses give shelter and protection to birds and beneficial insects, including butterflies, during summer storms and winter cold, so be sure to leave them stand all winter. Besides shelter, they also provide seed for the birds to eat. Highlight them during the winter by placing some up-lights in front of them.

Ornamental grasses need to be cut down in March just before their new growth begins. Tie a strong string or cord around the whole grass clump, then use your hedge shearers to cut it as close to the ground as you can get it. The string will hold the grasses together and keep the clump neat as it falls. Cut grasses can be used as mulch in the paths of the vegetable garden, or, I cut them into slightly shorter segments, and use them for mulch under big shrubs.

When you cut your grass down, you may notice that it is dying out in the center and is beginning to resemble a donut. This is a good time to rejuvenate the clump and also to get more plants. Dig up the entire clump, then cut it into segments. Replant the section you want to keep. Plant some other segments elsewhere, or give them away. Always keep newly planted segments hydrated the first year.

Ornamental grasses are often mentioned when discussing fall garden design because the warm season grasses are slow to develop in the spring and can take quite a while to mature. It generally takes until August or later for them to "flower" or develop their seed heads and mature color.

There are also cool season grasses available which tend to mature much earlier. My favorite grass in this category is Feather Reed Grass ‘Karl Foerester’ (Calamagrostis acutiflora Karl Foerster). This grass will grow quickly through May up to five feet tall, then flower in June. I love it because it not only matures early, it stands straight up on very sturdy stems, and doesn’t flop over other plants. In fact, it makes a lovely backdrop for other flowers in front of it.

If you shop for ornamental grasses you will be amazed by how many varieties, sizes, shapes, and colors are available. What to choose? When I want to buy any new plant for my garden, I always look at natives first and also consider the growing conditions the soil has to offer. Most ornamental grasses like full sun and neutral soil, but there are a few that prefer shady, moist areas.

Plant the tall native switch grass (Panicum virgatum) for a nice softening effect in the garden. Other nice native ornamental grasses, already mentioned, include Little Bluestem (Schizachyrium scoparium) and Indian grass (Sorghastrum nutans). These are each native to the U.S. and quite hardy in our area. They are known for the almost iridescent color splashes that appear in late summer and fall.

An eye-catching native to Western and Central U.S. is Muhlenbergia capillaris, commonly called pink muhlygrass. It is a clump-forming, warm season, perennial grass that is noted for its attractive summer foliage and spectacular clouds of pink fall flowers which distinguish it from any others. It likes moist soil and full sun.

There is also a wide variety of non-native, but garden-worthy grasses available such as the fountain grasses Pennisetum spp. Most varieties are hardy in our area, but the popular, Pennisetum setaceum ‘Rubrum’, is not. This is the attractive red grass which is often showcased in containers. We treat it as an annual although it is hardy in zone 10.

Please stay away from Miscanthus grasses which are known to be invasive. They have multiple varieties, many of which are very beautiful, but then, so are all the good choices. Many of the Miscanthus grasses become thugs in your garden, expanding rapidly and coming up in the middle of other plants. They can make you wish you had never met them!

Ornamental grasses are often used around the edges of ponds and streams because their dense root systems do a good job of binding the soil to halt erosion. Suitable grasses for planting around the water garden include prairie cordgrass (Spartina pectinata), ribbon grass (Phalaris arundinacea var. picta) and variegated manna grass (Glyceria aquatica ‘Variegata’).

Speaking of water gardens, rushes and sedges, which are grass-like plants, are also valuable additions because they prefer moist soil. Attractive species include yellow sedge (Carex elata ‘Bowles Golden’), umbrella sedge (Cyperus alternifolius), silver variegated Japanese sedge (Carex morrowii ‘Variegata’) and corkscrew rush (Juncus effusus ‘Spiralis’).

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