Grasses & Sedges in the Landscape

Gardening with flowering plants usually involves focuses on broad-leafed plants, which comprise the very large class of dicotyledons (“dicots”). In this column, we consider the monocotyledons (“monocots”), which include three families of narrow-leafed plants: grasses, sedges, and rushes. Dicots and monocots have several differences; most importantly, dicots have two embryonic leaves in each seed, while monocots have one.

Cultivation of these two classes of flowering plants has pretty much the same general requirements, plus the usual variations of specific plants. The narrow-leafed monocots, however, bring a distinctive form to the landscape and are also valued for such qualities as a gentle movement, drought tolerance, and low maintenance.

We might think of all garden-quality monocots as ornamental grasses, but grasses, sedges, and rushes each have unique shapes, which are described in a familiar rhyme: “Sedges have edges/Rushes are round/Grasses are hollow/What have you found?”

Gardeners can use ornamental grasses in several ways in the landscape. An excellent resource about many specific kinds of grasse and their uses is the exceptional book, The American Meadow Garden: Creating a Natural Alternative to the Traditional Lawn (Timber Press, 2009). Grass expert John Greenlee wrote this book, and garden photographer Saxon Holt provided excellent images. Their collaboration builds on their previous impressive works: Greenlee’s The Encyclopedia of Ornamental Grasses (with photography by Derek Fell) (1992) and Holt’s contributions to Nancy J. Ondra’s Grasses: Versatile Partners for Uncommon Garden Design (2002).

The sub-title of The American Meadow Garden emphasizes lawn grasses, but the book actually explores a variety of landscape uses of grasses: groundcovers, fillers, backgrounds, accents and natural lawns. Several grass varieties can be used in more than one of these ways.

Even a cursory scan of this book reveals an impressive range of garden-worthy grasses and their distinctive appearances. The garden designer is well advised to begin with a particular landscaping goal and then to look for grasses for optional approaches to meeting the goal.

My own current project, the development of a fairly large bed of Mediterranean basin plants, includes an interest in moving several existing sedge plants from another part of the garden. The plant is a European native, Grey Sedge (Carex divulsa). Interestingly, this plant had been — and might still be — sold as a California native plant called Berkeley Sedge or Foothill Sedge (C. tumulicola). It was correctly identified as C. divulsa in 2005.

Photo of Grey Sedge

Grey Sedge (Carex divulsa), often sold by the incorrect name, ‘Berkeley Sedge”

By any name, Greenlee calls this plant “by far one of the most versatile and manageable of all the groundcover sedges.” It grows twelve-to-eighteen inches high, and up to thirty-six inches wide, and is evergreen in the Monterey Bay area. It tolerates clay or sand and dry or moist conditions, and competes well with tree roots. It grows well in sun but prefers light shade. It’s true workhorse in the garden, and by most accounts attractive either as a single tussock or in larger areas.

This plant naturalizes easily to the point that some plant people consider it to be invasive. Unwanted seedlings can be removed easily enough, but gardeners should be aware of this plant’s ability to spread.

Grey Sedge will work well in the lightly shaded portion of my Mediterranean basin bed. I will plant divisions of the existing clumps about eighteen inches apart, and expect them to spread to form an interesting smallish meadow.

My specimens of Grey Sedge had been imposters in my California native bed, so their removal from that bed creates an opportunity to replace them with California native grasses. There are good options for accents and ground covers, to be explored in another column.