by the Western Massachusetts Master Gardener Association
September 2001 - Ornamental Grasses
by Christopher Hurn Amherst, MA
In the past few years, ornamental grasses have become very popular in Massachusetts gardens. Most garden centers now stock selections of the most popular grassesMiscanthus (Japanese silver grass), Pennisetum (fountain grass) and that old but invasive favorite, Phalaris picta (ribbon grass). Local nurseries, which might have carried four or five grasses a few years ago, now offer as many as 20 varieties and cultivars, from large Miscanthus, over seven feet tall, to shade-loving sedges less than six inches high. Ornamental grasses have grown in popularity because of their multi-season appeal, their versatility as landscape plants and their ease of maintenance. The graceful, arching form of Miscanthus sinensis (and, in some cultivars, its near-white or yellow-banded foliage) is attractive from June to October, while the plumes which rise above the foliage put on a spectacular show in the fall. Even in winter, the skeleton leaves remain defiantly upright. Other ornamental grasses grown for their leaf color as well as their elegant form have a long season of interest. Spiky blue oat grass (Helictotrichon) makes a splendid complement to pink or yellow flowers all summer long, while white ribbon grass (Phalaris picta) brightens a dull, partly shady spot from April to November.
Ornamental grasses are also highly versatile plants. A single specimen of zebra grass (Miscanthus sinensis 'Zebrinus') is a marvelous addition to a late summer border of rudbeckias and hot-colored annuals. A group of blue fescue grasses or the new Panicum 'Dallas Blues' are an ideal complement to pink, blue, and white flowers. The delicacy and informality of the larger grasses are also useful in foundation plantings, providing a foil for the formality of shrubs and house walls. And a line of the Miscanthus or Panicum grasses can serve as a screen between adjacent parts of the garden or even as an informal fence between properties. Several ornamental grasses are useful as a weed suppressing ground cover and a low maintenance substitute for lawn grasses. Thus Phalaris picta (ribbon grass) spreads quickly and grows densely enough to suppress weeds, and while invasive (but no more so than lawn grass), requires only one mowing, in late July or early August, to remain attractive from April to November. Pennisetum (fountain grass), while a little slow to get going in the spring, suppresses weeds as effectively as hosts, providing attractive bottle-brush plumes in August and September. In damp ground and in shade, sedges like Cares morrow) variegate are a very effective ground cover and a fine complement to ferns and hostas.
Most ornamental grasses are low maintenance plants, less exacting in their requirements for particular soils, drainage, and fertility than most perennials. Miscanthus, for example, will grow in low fertility soil and tolerates drought, but also grows well in moist locations with rich soil provided it has 6 hours of sun. Panicum (switch grass) and Sorghastrum nutans (Indian grass) are native to the Great Plains; they are able to handle temperature extremes and drought conditions which would be fatal for lawn grasses. All these grasses need a trim with hedge clippers in late winter or spring and, in the case of Miscanthus, division every four years or so to prevent their getting too large and dying out in the center. But that is all that is usually required.
Growing ornamental grasses in Western Massachusetts
Local garden centers feature ornamental grasses like Miscanthus, Panicum and Pennisetum in the late summer and early fall when these warm season grasses are reaching their peak. But although grasses planted at this time will usually survive, fall is not the ideal time to plant, and still less to move, these ornamental grasses. Gardeners in the colder parts of Western Massachusetts, where frosts come in September and the ground freezes early, should try to purchase container plants early in the season and reject root-bound specimens, especially with grasses which are only marginally hardy in Zone 4. At the same time, gardeners in the colder parts of our region are not at all at a disadvantage when it comes to growing cool season grasses like Calamagrostis, Phalaris, and Molinia. These grasses flower early in the year and look their best in early summer and fall, sulking a little in the hottest part of the summer. These grasses, along with early blooming Miscanthus are the best choice for Berkshire County; gardeners in Zone 5, on the other hand, are spoiled for choice.
Useful books about ornamental grasses include the Taylor's Guide to Ornamental Grasses (Houghton Mifflin, 1997) and Rick Darke's The Color Encyclopedia of Ornamental Grasses. Limerock Ornamental Grasses, Port Matilda, Pennsylvania (814-692-2272; www.limerockgrasses.com), is a good source for the more unusual and newer cultivars not available locally. Gardeners on a budget can grow most of the major species, including Miscanthus, Pennisetum, and Deschampia (though not the newer cultivars) from seed. Many seed companies carry ornamental grass seed, so check a number of catalogs for the best selection.