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The Grass is Always Greener

The Grass is Always Greener-When It's an Ornamental

Originally published in the Ithaca Journal in October, 2000
By Mary Hirshfeld

No garden should be without a selection of fall-blooming ornamental grasses. These large, late flowering ornamentals are categorized as warm season grasses--they are slow to get started in spring, and wait until the warm days of summer to really push new growth. They reach their full potential in the late days of summer and throughout the fall.

The most familiar and widely grown warm season grass is the Japanese silver grass (Miscanthus sinensis), a variable species from which many distinctive cultivars have been developed for home gardens. Plantations displays 28 of these cultivars throughout several gardens: the Peony Garden, North Walk, a double-sided border outside the north wall of the Herb Garden, and within the Flowering Shrub Collection. The one drawback that Miscanthus holds for most gardeners is its tremendous size. Many cultivars reach four to seven feet in height, making it difficult to site them well in a small garden. They are also a challenge to move and divide. A well established plant can take considerable effort with a digging bar, spade, and the assistance of several friends, to get it out of the ground. Despite these drawbacks, if your garden has sufficient room for one or more Miscanthus selections, they are well worth growing.

One of the oldest and most reliable Miscanthus cultivars is 'Gracillimus' a slender-leaved, portly selection that tops out at four to five feet. One of the few Miscanthus strains grown from seed, 'Gracillimus' plants are not always identical, but are remarkably consistent in form and can stay put for years without requiring division. 'Dixieland' is an introduction from Kurt Bluemel, a Maryland nurseryman who has been the driving force behind introducing and popularizing grasses in this country. Shorter and less husky than the older 'Variegatus', 'Dixieland' also sports bright green leaves boldly striped with white. To date, it has remained relatively compact and manageable in height at its location on Plantations' North Walk. Other cultivars that share the white variegation but can reach heights of six to seven feet are 'Rigoletto', 'Cabaret' and 'Cosmopolitan'. A very diminutive, extremely slow-growing, narrow-leaved, white-striped selection is 'Morning Light'. This lovely plant, although slow to establish itself and reach its full potential, is an excellent selection for smaller garden spaces.

Several cultivars offer yellow variegations of differing patterns. The oldest of these is zebra grass or 'Zebrinus', a very vigorous grower with striking horizontal yellow stripes marching across the tall green foliage. Two slightly more compact models are porcupine grass or 'Strictus', named for its very erect habit and bristly, quill-like leaves; and little dot grass or 'Puenktchen', also bearing slender, stiffly erect leaves. The many cultivars of green-leaved Miscanthus are difficult to separate unless seen at a distance, where differences in habit, texture, flower carriage, and color become more apparent. One that always stands out and elicits admiration is 'Sarabande', a tall, graceful Kurt Bluemel selection with exceptionally slender leaves that are simply radiant in the low-angled autumn light.

Until very recently, Miscanthus was one of those rare groups of plants considered "pest and disease free." Now, two major pest problems are emerging. Because both are new, effective, least-toxic solutions have not yet been worked out. Miscanthus mealybug is a soft-bodied, white, wooly insect that can be found between the clasping leaf sheath and stem, particularly on the lower portions of the grass. Heavy infestations can stunt plant growth, resulting in bunched foliage and twisted flowers that open within the foliage rather than well above, where their graceful delicacy can be admired. The mealybugs have been transferred from contaminated nursery stock to gardens, and have become quite widespread. A second problem is Miscanthus blight, caused by a rust fungus that appears as reddish-brown spots on the foliage. These gradually coalesce into large brown areas, resulting in the death of most or all of the foliage.

Two years ago, I would have enthusiastically recommended switch grass (Panicum virgatum) and its many lovely selections as must-haves for any garden. This native grass offers a number of variants--some with steel-blue foliage, others with vibrant tints of scarlet. All produce clouds of delicate flowers that float above the foliage throughout late summer and well into fall. But for the last two seasons, many of the blue-leaved Panicums in the Flowering Shrub Collection here at Plantations have been afflicted with a still-unidentified rust that starts in early summer as a series of small red spots on the foliage. These rapidly coalesce into larger brown streaks, leaving the foliage blackened and ruined by August. The green and red-tinted switch grass varieties have not been affected. So I would suggest steering clear of such enticing silver blues as 'Heavy Metal', 'Warrior', and 'Prairie Sky' for the time being. Among those safer selections that take on strong scarlet tones in late summer, and hold up through several hard frosts are 'Rotstrahlbusch', 'Rotbraun', and the relatively new 'Shenandoah'. A mass planting of 'Rotstrahlbusch' graces the slope that rises from the Herb Garden to Judd Falls Road. There, its three-foot-tall scarlet-tipped leaves glimmer in the autumn sun.

The fountain grass family (Pennisetum alopecuroides) offers a variety of smaller-statured grasses, ranging from 18 inches to three feet. Their form and texture are notably different from either Miscanthus or Panicum. 'Moundry' and 'National Arboretum', are both fountain grass selections with wider leaves and dark purple-black flower spikes held close to the foliage. While not always reliably winter-hardy in our area, they are worth trying, and overwinter most successfully in a sunny, well drained spot. Selections with the more typical slender leaves and dark brown bottlebrushes waving gaily above a fountain of dense foliage include 'Hameln', slightly smaller than the type; and 'Herbstfeuer', with longer flower stems and very slender foliage.

The most dramatic grass at Plantations is hardy pampas grass (Saccharum ravennae), often still sold as Erianthus ravennae. This giant reaches a solid 12 feet in height, its stems topped by flamboyant triangular plumes similar to those of the more common pampas grass (Cortaderia selloana), which is reliably hardy only to zone 7. Erianthus is one of the few grasses I would recommend as a reliable ornamental for a winter garden, as the strength of its stems can usually withstand the heavy wet snowfalls and ice coatings that would turn Miscanthus, Panicum, and Pennisetum into a tangled mess of shattered flower stems and flattened foliage. Ornamental grasses are at their peak at Plantations now, so come visit, and be sure bring along a notebook to record the names of those that catch your eye!