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Tuesday, April 23, 2024

Everything You Need to Know About Ornamental Grasses

CRL's gardening expert on how ornamental grasses can star in your fall garden.

Ornamental grasses are the ‘grand dames’ in the fall garden.  Their dramatic plumes dance in the autumn breeze and are especially breathtaking when backlit by afternoon sun.

Grasses come in a range of heights, colors, blade widths and stature.  Mature heights can be as petite as 6” (Black Mondo Grass) or soar to over 12’ (Miscanthus ‘Giganteus’).   Blade colors can be shades of green as well as blue, yellow, black, burgundy-red or bi-color.  Some grasses have extremely narrow blades (Carex ‘Bowles Golden’) while others have girths of an inch or more (Carex ‘Banana Boat’).   Their ‘postures’ can be narrow and upright, (Calamagrostis ‘Karl Foerster’); short and spikey (Blue Oat Grass) vase-shaped (Miscanthus ‘Morning Light’) or cascading (Japanese Forest Grass).

Ornamental grasses fall into two categories as far as flowering time.  Cool season grasses bloom in early to midsummer.  Examples in this group are Blue Fescue and Blue Oat Grass.  Warm season grasses are prized for their showy displays.  Switch Grass (Panicum), Fountain Grass (Pennisetum) and Miscanthus are popular picks.  Bloom colors can be white, cream, rose, tan or pink.

When buying ornamental grasses, make sure you select ‘clumpers’, not those that spread rapidly by renegade roots (rhizomes) or above-ground stems (stolons).  Ribbon Grass (Phalaris) is one of those ‘enthusiastic’  grasses that will follow you into the house if you let it.  One way to control their march is to sink them in a 3’ or 5’ pot.   If the plant tag description is not clear about how they grow, ask.

Grasses provide wonderful winter interest as well. Leave them be in the fall. You may want to stake larger grasses so they keep ‘good posture’ in winter after it snows. Prune the foliage to within 2” to 3” of the ground in late winter or early spring. Use a power hedge trimmer or sharp pruning shears for larger grasses. To save time raking up blades, place twine, bungee cord or duct tape around the plant’s ‘waist’ before whacking. Some grasses have razor-sharp blades so use protective gloves when handling them. Shorter grasses like Blue Fescues can be ‘deadleafed’ by simply running your fingers through the clump and pulling out brown foliage.

The best time to divide grasses is in late winter or early spring after you’ve cut them back or ‘combed’ them. Depending on the grass, you may need a saw, ax, machete or chainsaw to get through the dense root mass. Keep going, don’t let it get the best of you.

Most ornamental grasses prefer full sun and are quite drought tolerant.  But there are also shade lovers that make terrific companions with Hosta, Astilbe and Bleeding hearts.  All grasses are deer resistant.  Bravo!

Below are some of my favorite grasses for the Capital Region

Japanese Forest Grass, Hakone Grass (Hakonechloa)  12” – 24” tall.  Part to Full Shade. Late summer, fall bloomer. Creamy-tan flowers. This is a lovely, cascading grass. It does a superb job softening edges. ‘Aureola’, with shimmering gold and green variegated blades, was the Perennial of the Year in 2009. ‘All Gold’ has a more upright habit with solid gold leaves. ‘Albo Striata’ is green and white and ‘Beni Kaze’ starts out green and then reddens in cooler weather. Zones 5 – 9

Blue Fescue (Festuca) 6” – 12” tall.  Sun.  Summer bloomer. Tan flowers. Stiff, porcupine-like blue blades create striking textural interest. ‘Elijah Blue’, ‘Boulder Blue’, ‘Blue Glow’ and ‘Blue Fox’ are intense blue. These benefit from dividing every three or four years to keep their compact habit and rich coloring. I don’t prune Fescues in spring, I ‘comb them out’. Zones 3-8

Japanese Blood Grass (Imperata cylindrica) 1’ – 2’ tall. Sun to Part Sun. Late summer, fall bloomer. Creamy-white flowers.  Japanese Blood Grass has slender green blades that become rich burgundy-red in late summer. When backlit by the sun, this grass is mesmerizing. Zones 5 – 8

Fountain Grass (Pennisetum) 6” – 4’tall.  Sun to Part Sun. Summer bloomer. Tan to rosy-pink flowers. There are many great choices in this family. ‘Little Bunny’ only gets 6”- 12” in bloom, ‘Hameln’ hits the 24” – 30” mark, while ‘Karley Rose’ displays nicely arching 40” blades. These are just a few of the great clumpers available. Zones 5 – 9

Little Bluestem (Schizachyrium) 2’ – 3’ tall.  Sun. Summer bloomer. Silvery flowers. This native grass defines elegance. It has extremely narrow, fine blue blades with some maroon coloring later in the summer. Little Bluestem sways sublimely in summer and fall breezes.  ‘Prairie Blues’ has a more upright habit than the species.  Zones 3 – 10

Japanese Silver Grass (Miscanthus) 3’ – 12’ tall.  Sun. Late summer, fall bloomer. Silver, tan, burgundy and reddish-tan flowers. This is another family with many tried and true performers for colder climates. Great picks include ‘Zebrinus’ (horizontal gold bars on green blades, 7’ – 8’, Zone 5),

‘Silver Feather’ also called ‘Silberfeder’ (narrow green blades, 9’, Zone 4), ‘Gracillimus’ (narrow green arching blades, 7’, Zone 5), ‘Graziella’ (green blades with large silver-white flower, 6’, Zone 5),

‘Purpurascens’ (green blades that turn reddish in cool weather, 6’, Zone 4), ‘Morning Light’ (very narrow green and white arching blades, 5’ – 6’, Zone 5), ‘Dixieland’ (wider green and white blades, 4’, Zone 5),

‘Variegatus’ (like ‘Dixieland’ but taller, 6’, Zone 5) and ‘Huron Sunrise’ (green blades with white centers and burgundy plumes, 5’ – 6’, Zone 4).

Switch Grass (Panicum) 3’ – 8’ tall. Sun. Late summer, fall bloomer. White and rosy-pink flowers. Many Panicums are more upright and less sweeping than Miscanthus grasses. Outstanding cultivars in this family include: ‘Heavy Metal’ (upright, steel blue blades with white flowers, 5’ – 6’, Zone 3),

‘Shenandoah’, ‘Cheyenne Sky’ and ‘Prairie Fire’ (all have green and burgundy blades, 3’, Zone 3),

‘Prairie Sky’ (powdery blue blades, 6’, Zone 3) and ‘Cloud Nine’ (blue blades, 6’, Zone 3).

Feather Reed Grass (Calamagrotis) 4’ – 5’tall.  Summer bloomer. Tan flowers. A stiff, upright grass that works well in narrow spots. ‘Karl Foerster’ with solid green blades was the Perennial of the Year in 2001. ‘Overdam’ mixes it up with green and white blades while ‘Eldorado’ has green and gold blades. All are hardy to Zones 3 – 7.

There is also a bushel full of annual grasses that are nifty additions to containers and gardens but that’s for another column.

If you are looking for low-maintenance, high-return perennials for year-round interest, then ornamental grasses will sweep you off your feet!

Kerry Ann Mendez is a garden designer, speaker, teacher and writer and the owner of Perennially Yours in Ballston Spa. Visit her website at www.pyours.com

Kerry Ann Mendez
Kerry Ann Mendez
Kerry Ann Mendez is the owner of Perennially Yours, as well as a speaker, author and expert gardener.

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