There is a widespread assumption among gardeners that trees and grass don’t mix. Indeed, most grasses are sun lovers, and even shade-tolerant fescue turf fails to thrive when it has to compete with the surface roots of mature shade trees. Likewise, many tree species suffer when subjected to the typical maintenance regimen of a lawn: spraying the trunk with a sprinkler all summer long is a recipe for crown rot. Many long-lived trees, like oaks and beeches, prefer a deep soaking every few weeks, not every other day like a lawn.
However, in the deciduous forests of the world, one can often find exquisite glades of grass, or grass-like plants, thriving beneath mature trees. How can that be? These are clump-forming (as opposed to turf-forming) species that have co-evolved with native trees, and especially with forested savannas and other forest ecosystems where the trees cast relatively light shade. Unlike the shallow, fibrous mat of roots found in turf grasses, the roots of clump-forming grasses, also known as bunch grasses, tend to grow more down than out, a trait that makes them less competitive with lateral tree roots.
While virtually no grass is compatible with the deep shade of most conifers, or beneath large evergreens like the southern magnolia, there are a number of striking ornamental grasses suitable for planting beneath most high-canopied deciduous trees, like elms, oaks, and maples, and smaller, narrow-canopied trees, like gingkoes, birches and crepe myrtles. These range from Japanese forest grass, with its many brightly colored cultivars, to elegant natives such as river oats.
Designing with Grasses for the Shade
A lush, grassy grove of trees makes for an enchanting landscape feature. For design inspiration, start by looking to the natural ecosystems where trees and grasses are found together. They often grow in harmony along the moist banks of rivers, lake, and ponds. (Though in this instance, it’s often sedges, reeds and rushes that you’ll find amid the willows and cottonwoods, rather than true grasses—but the effect is the same.) High, rocky ridge tops are another zone where grasses and trees often commingle, in part because the naturally stunted growth of the trees in these landscapes leaves plenty of light at ground level for grasses to colonize. These habitats are suggestive of design elements such as water features, dry streambeds and rock gardens. Match your choice of grasses to the landscape style you’re going for.
In North America, the oak savannas of the West Coast—such as the famous “golden rolling hills of California”—are among the best-known forest–grass ecosystems, where widely spaced native oaks tower over an astonishing array of grass species, including some that are common in the nursery trade through the country, like blue fescue. Similar environments occur in pockets throughout the Southwest and Midwest. The pine barrens of the East are another example where tall, widely spaced trees with narrow leaves that cast little shade, providing prime habitat for bunch grasses.
If you’re looking to plant under trees where there is plenty of filtered light throughout the day and a few hours of direct sun in morning or afternoon, the entire palette of bunch grasses are available to you, from bushy, vibrant purple pennisetums to the thin and graceful feather reed grass. But if light conditions are reduced—part shade, rather than part sun—your choices remain more limited. Here is a round-up of a few of the most striking shade-tolerant grasses and grass-like plants.
Ornamental Grasses for Shade
Japanese forest grass (Hakonechloa macra)
Growing to approximately 12 inches in height, this species forms a riverlike pattern of foliage that flows gracefully around boulders, ferns and other upright perennials and shrubs. Of all grasses, it is unparalleled in a Japanese garden setting. It comes in a range of golden, chartreuse, rose-tinted and variegated forms that brighten up any partly shaded area. These tolerate full shade, but their colors may not be as vivid there. USDA Zones 4 to 9.
River oats (Chasmanthium latifolium)
An upright grass with attractive seed heads (the “oats”) that rise to four feet above narrow clumps of foliage. This eastern native is often found along forested streams. While it tolerates wet soil, it also thrives in average moisture conditions. It is an excellent choice for large naturalized gardens, as it seeds itself prolifically, forming an extensive glade. It is fully shade tolerant. Zones 4 to 9.
Tufted hair grass (Deschampsia cespitosa)
This native plant can be found in savannas and open forests throughout North America. It forms a neat tussock of fine foliage about 12 inches tall and wide, above which airy sprays of buff-colored seed stalks rise in the fall. This species thrives in part shade, but it will not tolerate full shade. Zones 4 to 9.
Korean feather reed grass (Calamagrostis brachytricha)
A native of Asia, this is a shade-tolerant relative of the perennially popular ‘Karl Foerster’ feather reed grass; it bears similar feathery brown seed stalks, which persist into winter as an off-season accent. A moisture-lover, it thrives in wet soil, unlike its more well-known cousin. This upright specimen grows two to three feet wide with seed stalks up to five feet tall, and it tolerates part shade only, not full shade. Zones 4 to 9.
Clumping fescue (Festuca)
While turf-forming fescues are the most shade-tolerant of lawn grasses, the many species of clumping fescue also fare well in partial shade, and these are a better choice under mature trees than the lawn varieties. They include a number of native drought-tolerant species, most of which form tidy clumps no more than 12 inches tall and wide. Among the most striking cultivars are the blue-gray varieties ‘Elijah Blue’ and ‘Siskiyou Blue’; be forewarned, however, that the colors are not as vivid in shade plantings. Zones vary by species.
Sweet flag (Acorus)
Also referred to as Japanese rush, there are two basic forms of this grass-like plant: Acorus calamus, a tall version (up to 30 inches) with strap-like foliage reminiscent of an iris; and A. gramineus, a short version (under 12 inches) with finer foliage. Both are available in a number of colored and variegated cultivars. They require constantly moist soil; in fact they tolerate shallow water, making them an ideal choice for edging around shaded water features. Zones 4 to 10.
Sedge (Carex)
There are about 2000 species of sedge, a large percentage of which tolerate shade. Most grow in neat mounds ranging from 6 to 24 inches tall and wide. Cultivars abound in a wide variety of colors, including gold, blue-gray and bronze. Colorful ‘Ice Dance’ (shown above), ‘Silver Sceptre’, ‘Kaga-nishiki’, ‘Blue Zinger’, ‘Evergold’, ‘Everillo’, ‘Variegata’, and ‘Aurea’ number among the most shade tolerant. Some like it dry and some like it wet, so check the label for growing conditions before purchasing. Zones vary by species.
Monkey grass (Various genera)
Known variously as monkey grass, mondo grass and lily turf, these grasslike plants, which include species of both Liriope and Ophiopogon, actually fall in the asparagus family. They take full shade and they are nearly indestructible. But beware: some of the varieties are a bit too so and can become highly invasive, especially the species L. spicata. The dwarf and colored cultivars, which range from 2 to 24 inches and span the spectrum from chartreuse to variegated to nearly black, are generally not as aggressive as the plain green varieties. Zones vary by species.
Wood rush (Luzula)
These shade-tolerant relatives of the popular juncus rushes are largely known for their glossy green foliage, though the species Luzula nivea, or snowy woodrush, possesses puffy sprays of white “flowers” that are equally enchanting. Most varieties grow one to two feet tall and wide and, like other rushes, they prefer rich, moist soil. Zones vary by species.
Image courtesy of Walters Gardens
