Monday, August 22, 2011

Dig In- Tips from Nettie at Uncanoonuc

Ornamental Grasses

Ornamental grasses have come into their own as more and more gardeners get to know them and embrace their many attributes. There are grasses for every garden from an intimate doorway vignette to expansive municipal plantings. Some are imported beauties, but many are our own native daughters. They offer texture, structure, movement, contrast, color and multi-season appeal. Their flowers and foliage often make wonderful subjects for arrangements, fresh or dried. Most are low maintenance perennials. This is a brief introduction to some great grasses, tried and true performers here at Uncanoonuc. As their popularity continues to soar, more and more different grasses are being introduced - an exciting prospect for us all.

Cool Season Grasses

This group starts growing very early in the season and often are semi-evergreen in northern gardens. Adequate moisture during the growing season, especially in dry spells, is important to their overall health and beauty.  Dividing them every three years or so keeps them vigorous and looking their best. Early spring cleanup involves removing only the spent foliage - a job often best accomplished by finger combing the clumps. Fescue and Blue Oat Grass are examples of cool season grasses.

Warm Season Grasses

This group goes totally dormant during the winter and doesn’t resume growth until the soil has warmed up in late spring. Many are in their full glory in late summer and fall and offer winter interest in the garden. They tend to be very drought tolerant and division is required much less frequently. Early spring cleanup involves a hard haircut - cutting last year’s growth back to 6” or so from the ground. On larger clumps a string trimmer with a blade attachment is a big help. Some people bungee cord the spent foliage together before cutting to make a neater job of it.  Switch Grass and Fountain Grass are examples of warm season grasses.

image courtesy of Univ. of California

“Right plant, right place.” This mantra is as important for ornamental grasses as it is for all garden plants. A grass growing under conditions it favors thrives with minimal effort. It is true that most are sun lovers, but there are grasses for shady sites. Meeting their light requirements is key to success. We feed our grasses lightly in early spring and, in rainy years, again - very lightly - in early summer. They are not heavy feeders. We clean them up (see above) as soon as the snow is gone. We use bark mulch around our grasses, like the rest of the gardens, to keep the weeds down and the gardens looking pretty. Winter mulch on the varieties we offer is not needed. The grasses described below are all clump formers. Their crowns increase in size each year, but they are not spreaders. Blue Lyme Grass and Ribbon Grass are two attractive grasses that do spread aggressively. They are best used as ground covers where this characteristic is an attribute. Confining the roots with a sturdy sunken barrier is highly recommended if they are to be grown in a mixed planting. Concerns about some grasses becoming invasive from self-sowing are legitimate from the mid-Atlantic states and warmer areas, but luckily are not an issue this far north.

Blue Lyme grass
Small Grasses

Prairie Dropseed (Sporobolus heterolepis) -  A warm season grass for full sun or light shade, this native forms a tousled mop of very fine-textured, glossy, deep green foliage topped with a diaphanous cloud of beige flowers in late summer. Like many grasses, the flowers are especially effective backlit by morning or late day sun. The foliage becomes a striking orange in the fall and then assumes a pretty copper color during the winter. Despite its name, Prairie Dropseed does not self-sow here. It will rarely, if ever, need dividing. Effective in a small garden paired with bolder foliage and flowering plants, as a very low maintenance ground cover or in a naturalized area.

'Elijah Blue' Fescue
‘Elijah Blue’ Fescue (Festuca glauca cultivar) -  A cool season grass for full sun, this is the bluest and most popular of the many blue fescues available. It forms a dense clump of spiky, glaucous silver-blue foliage which is attractive year round, and is topped in early summer by upright, arching flowering stems that make me think of fireworks. The pleasing flowers emerge blue-green, fade to the color of straw and should be snipped off in mid-summer, so they don’t detract from the beauty of the foliage. The tufted habit and striking color offer a myriad of design possibilities. If used in large drifts as a ground cover, remember it will need to be rejuvenated by division every few years.

Carex 'Silver Scepter'
Sedges (Carex species and cultivars) - An enormous group of grass-like plants from the family Cyperaceae (true grasses are in the Poaceae family). The flowers are interesting at best; for sedges the glory is all in the foliage. Thriving in partial shade in moist soils, they adapt to deeper shade and - with adequate moisture at the root - full sun. Handsome ‘Ice Dance’ (Carex morrowii cultivar) forms arching mounds of long, narrow, shiny green leaves edged in creamy white. ‘Silver Scepter’ (Carex morrowii cultivar) is very graceful with arching mounds of very narrow, very long green leaves edged in silvery white. They spread and make excellent groundcovers but are not invasive.  They are semi-evergreen for us and can be cleaned up in the spring like cool season grasses. Every few years they benefit from being clipped back in the spring to clean up old, congested foliage. Creeping Broad-leafed Sedge (Carex siderosticha ‘Variegata’) forms dense clumps of pointed, strappy green leaves edged and striped with creamy white. ‘Treasure Island’ (Carex ciliatomarginata cultivar) also forms dense mats, its more blocky foliage edged and striped with bright white. These sedges make wonderful edgers, spreading but never aggressively. They are deciduous and should be cut back every spring like warm season grasses. Durable, low maintenance and attractive, sedges can add great textures and color to mixed plantings or containers.

image of Hakonechloa 'Aureola' taken at Heronswood Nursery courtesy of Univ. of Kentucky

Golden Japanese Forest Grass (Hakonechloa macra ‘Aureola’) - A warm season grass that forms cascading mounds of narrow golden leaves striped with green. The effect is reminiscent of a waterfall. Best in partial shade in fairly rich, but well-drained soil. There are other wonderful Japanese Forest Grasses (‘Naomi’ has showy maroon fall foliage color) but this one’s my favorite. Its habit is elegance personified. Its color is stunning. A natural near a water feature, equally handsome playing off different colored and textured foliage - think Hostas and dark leaved Coral Bells. 

Medium Sized Grasses

‘Sapphire’ Blue Oat Grass (Helictrotricon sempervirens cultivar) - A cool season grass for full sun and well-drained soil that forms a tufted clump of spiky silvery-blue foliage. It’s topped in early summer with long, slender wands of arching blue-green flowers that age to beige. The faded flower stalks should be clipped off to let the stellar foliage shine. Reminiscent of the Blue Fescues, but larger and with a looser more graceful habit. Depending on the garden’s size, ‘Sapphire’ could be used effectively as a specimen or in drifts.

Purple Fountain grass
Fountain Grasses (Pennisetum species and cultivars) - A large group of warm season grasses best in full sun, tolerating partial shade. ‘Hameln’ forms a neat, rounded mound of fine-textured foliage that’s topped from late summer through the fall with an explosion of long, dense, foxtail-like plumes. ‘Little Bunny’ is very similar in habit but, as the name suggests, is a miniature. ‘Karley Rose’ is a standout Fountain Grass blooming from mid-summer on, its slender foxtail flowers decidedly pink. The popular Purple Fountain Grass is an annual Pennisetum. This one’s often featured as a dramatic container plant - a role it excels at. Other Pennisetums could be used this way and are also lovely in the mixed border or as a ground cover. A dew drenched clump of Fountain Grass, each flower plume magnified by droplets of moisture, is a study in ethereal beauty.

‘Golden Pendant’ Tufted Hair Grass (Deschampsia cespitosa cultivar) - A cool season grass for full sun or partial shade and moist soil. The clumps of narrow green foliage are topped in early summer with a cloud of airy, pendulous, green-gold flowers. Tufted Hair Grass is especially effective en mass and nothing short of glorious when the profuse blooms are backlit.

‘River Mist’ Wild Oat Grass (Chasmanthium latifolium cultivar) - This gorgeous, clump forming native is a warm season grass thriving in partial shade and fairly rich, moist but well-drained soil. It boasts vivid green and white variegation and a bamboo-like look. It is topped in late summer with pendant clusters of flattened, silvery seedheads that dance in the breeze. The flowers give a long show in the garden, and are a favored cut flower, fresh or dried. Wild Oat Grass (Chasmanthium latifolium) is larger overall with the same look, minus the variegation. Preferring the same conditions, it’s more adaptable to various light and soil conditions. It may self-sow a bit, but never obnoxiously. Divide every five years or so.

Schizachyrium scoparium 'The Blues'
‘The Blues’ Little Blue Stem (Schizachyrium scoparium cultivar) - This warm season grass is one of the showiest selections of this highly variable native. Very upright, narrow clumps of intensely blue-green foliage whose tiny flowers are effective when they dry and add a silvery sheen to the tops of the stems late in the season. The fall color is striking when the foliage assumes red and purple hues. Grow ‘The Blues’ in full sun in average to sandy soils. Shade, too rich a soil or too much water cause it to flop. Gorgeous with a mixed planting of like-minded perennials like ‘Autumn Fire’ Sedum and Bearberry, and magnificent in a large grouping swaying in the breeze.

Large Grasses

‘Zebra’ Grass (Miscanthus sinensis cultivar) - An old favorite from an enormous group of species and cultivars, this warm season grass develops horizontal golden bars across its bright green leaves when the warmth of early summer arrives. It always looks like sun is streaming through the clumps even on cloudy days. Zebra Grass thrives in full sun in average to moist, well-drained soil. Fluffy, reddish then silvery-beige flower clusters top the huge foliage clumps in late summer. If ‘Zebra’ Grass and the other large Miscanthus are given adequate room and planted in the background they can be left indefinitely. In smaller gardens they may need division every five or six years. This is a job for early spring, a sharp spade and a strong back. Wear gloves whenever you work with Miscanthus as many have sharp edges and can slice skin like paper cuts. Ouch! ‘Little Kitten’ and ‘Adagio’ are more petite Miscanthus easy to use in smaller gardens. ‘Silver Feather’ whose flowers are held high above the foliage and (like many Miscanthus) remain effective into the winter months,  is reminiscent of the Pampas Grass of the south. Giant Chinese Silver Grass is the largest hardy ornamental grass, a behemoth with potential for high drama. 

Miscanthus 'Adagio'

Siberian Greybeard (Spodiopogon sibiricus) - A clump forming  warm season grass thriving in full sun or partial shade, adaptable to varying soils but best in fairly rich, well-drained soil. Siberian Greybeard makes neat, very rounded mounds and holds its broad leaves horizontally giving the plant a distinct bamboo-like look. It’s topped with airy, buff-colored flower heads in late summer and develops rich maroon fall foliage color. Handsome alone or in groupings. Divide when and if the clumps develop an open area in the center, what we call the donut-effect.  

Panicum virgatum 'Shenandoah'
‘Shenandoah’ Switch Grass (Panicum virgatum cultivar) - A warm season grass, this is one of many highly ornamental selections of the native species. It thrives in full sun and is adaptable to many different soil types. Graceful, upright foliage clumps develop red tints mid-summer that deepen as the season progresses. It’s topped with clouds of airy flower heads studded throughout with glossy, garnet colored seeds. ‘Northwind’ Switch Grass forms a strong column of glaucous blue-green foliage, topped with clouds of airy golden flowers in late summer. This one has yellow-gold fall foliage color. A diverse group of easy to grow grasses. Divide every five years or so.

Calamgrostis 'Karl Foerster'
‘Karl Foerster’ Feather Reed Grass (Calamagrostis x acutifolia cultivar) - Thrives in full sun in average to fairly rich, well-drained soil; tolerates partial shade and less than ideal soil conditions, even clay. Feather Reed Grass is a cool season grass, but this one we cut back to about 6” early each spring. It is upright in habit, but never stiff, swaying in the breeze, rebounding after pummeling rains. The narrow, vertical flower wands -reddish at first, aging to beige - that emerge in early summer, accentuate the vertical effect and persist through the whole season and into the winter. Its ease of culture and multi-season beauty made it the Perennial Plant of the Year in 2001, the first grass to be so honored. Richard Darke suggests that those characteristics coupled with its fast growth make it an excellent choice for use as a seasonal screen. Slightly smaller varieties overall, ‘Overdam’ is variegated with creamy stripes, ‘El Dorado’ with gold.

Recommended Reading

The Encyclopedia of Grasses for Livable Landscapes - With a global perspective on grasses’ place in the world, Richard Darke’s outstanding offering has it all - design theory, detailed descriptions, practical cultural information, stunning photography and more. A gorgeous Timber Press release, but this is so much more than a coffee table book. Highly recommended. Click on the book for more info.

For more gardening tips from Nettie at Uncanoonuc, click here.

To learn more about Uncanoonuc Mt. Perennials, visit their website at


  1. Great article on grasses! Thank you!

  2. Helen, thanks for the nice comments! And, I'll pass them on to Nettie.--Joe


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