The Families of Grasses

True grasses

This plant family of some 650 genera and around 10,000 species contains many familiar plants. Bamboo, lawn grasses and the well-known cereals are all grasses. Ornamental species such as the fescues (Festuca), fountain grass (Pennisetum), Chinese silver grass (Miscanthus), pampas grass (Cortaderia) and switch grass (Panicum) are just a few noteworthy members.

Botanists refer to the stems of grasses as culms. These are round and usually hollow, and they differ from the culms of sedges which are characteristically solid and often three sided. Swellings at intervals along their length, called nodes, are the growing points of a grass from where the leaves emerge. This stands in marked contrast to other flowering plants whose stem tips form the growing points. The leaves offer protection to the nodes by sheathing the culms below them and by growing shield-like filaments above them.

More characteristic of individual grass species is the shape of their flower heads or inflorescences. Grasses are wind-pollinated and have no need for showy flowers, usually a feature of insect-pollinated plants. Their actual flowers are quite tiny but generally present in large numbers. They are gathered together into spikelets, the full complement of which is collectively referred to as the inflorescence.

The arrangement of the spikelets determines the general appearance of the flowering grasses and is important in their classification and description. There are three basic arrangements: the spike is an unbranched, elongated inflorescence, its spikelets attached directly to the axis or main stem of the flower head, resulting in a tight, narrow arrangement; the raceme is a slightly looser arrangement, with the spikelets growing away from the axis on short stalks; the panicle is the most delicate of the three structures, with its spikelets held out on branches.

The sedge family

Sedges are fewer than grasses; however, they are still a relatively large family of approximately 115 genera and 3600 species, nearly all of which are perennial. The botanical name of the family is derived from the genus Cyperus. Like grasses, sedges are a cosmopolitan group. They are found in most parts of the world but are especially common in wet or moist habitats in temperate and sub arctic zones, where they play an important role in soil stabilization. Most sedges are sun loving, but there are also many species native to shady wooded environments.

Sedges are unimportant as food sources for humans or domesticated animals; however, there are a few edible sedges as well as several species employed for other economic purposes. The Chinese water chestnut, Eleocharis dulcis, is cultivated for its edible tubers, as is the chufa or earth-almond, Cyperus esculentus var. sativus. The stems of Egyptian paper-reed or papyrus, C. papyrus, were the raw materials used to make the papyrus paper of classical antiquity. The bulrush, Schoenoplectus tabernaemontani, and various other sedge family members are used in basketwork, mat weaving, and the making of chair seats. Aromatic oils from the roots of galingale, C. longus, are used in perfumery. The fluffy heads of cotton grass, Eriophorum species, have been used in pillow stuffing.

Besides fibrous roots, most sedges have either rhizomes or stolons from which new plants are produced. Some sedges are tufted in their growth; others form spreading mats. Several stem and leaf characters make it possible to distinguish sedges from grasses. The stems of sedges are solidly filled with pith and lack nodes. They are triangular in cross section. The leaves are arranged in three rows, and their sheaths are usually fused around the stem. The leaf blades of sedges are grasslike, but ligules are usually absent or very much reduced. The foliage of many sedges is evergreen or semi-evergreen, ranging in color from greens to near-yellow, blue, and reddish browns. The leaves of many cultivated varieties are dramatically variegated.

Sedges are wind-pollinated, and the individual flowers are generally inconspicuous, without recognizable sepals or petals. The flowers are often but not always grouped in spikelets. The flowers or spikelets may be arranged in various spikes, umbels, or panicles, but sedges never develop the large open panicles or dense, plume like panicles common to the grasses. Reduced leaves or bracts are often present at the base of the sedge inflorescence. In the genus Rhynchospora these bracts are attractively suffused white. Some sedge family members have bisexual flowers, although many, including the large genus Carex, have male and female flowers grouped in separate spikes within the inflorescence of a single plant. The female flowers of Carex are commonly enclosed in a saclike structure called a utricle or perigynium. These structures are enlarged and curiously attractive in Gray's sedge, C. grayi. There are sedges with nearly black flowers, such as C. nudata, and truly red flowers, such as C. baccans; however, the flowers and inflorescences of most sedges are subtle greens and off-whites, and they rarely produce the dramatic luminous effects of true grasses.

The rush family

Though found worldwide, the rushes are a small family of only 10 genera and less than 400 species. Most are perennial herbs, growing primarily in wet or damp habitats in cool temperate and sub arctic regions. Annual species are uncommon. The family is of minor economic importance as the source of various fibers and binding materials. Prionium, the only shrubby genus in the rush family, includes the South African palmiet, P. palmitum, the leaves of which are the source of a strong fiber called palmite. The sea rush, ]uncus maritimus, is the source of the binding material known as juncio, and stems of the common or soft rush, J. effusus, are used in the making of baskets, chair seats, and various types of mats, including Japanese tatami.

Perennial herbaceous rushes usually have hairy roots and horizontal or erect rhizomes. The stems are erect, cylindrical, and solid. The leaves are mostly basal and are sometimes reduced to sheaths only. Like grasses and sedges, rushes are wind-pollinated and their flowers are quite small and subtle in coloration. They are most often green, brown, or near-black, but are occasionally white to cream-yellow. Though tiny, the flowers bear a close structural resemblance to lily flowers, having six similar tepals arranged in two whorls. Most rushes have bisexual flowers, each with six stamens and an ovary with three stigmas. Some have male and female flowers on separate plants. The numerous small flowers are arranged in panicles, clustered heads, or corymbs.

Only two genera are important to ornamental horticulture, Juncus, the rushes, and Luzula, the woodrushes. Both are perennial herbs. Rushes prefer wet sunny habitats and tend to be summer-flowering. Their leaves typically arise from the base of the clump and are cylindrical, resembling the stems. Woodrushes are native to moist or dry shaded habitats, blooming in spring or very early summer. Usually evergreen, their leaves are also mostly basal, but their blades are flat, usually with conspicuously hairy margins.

The restio family

Relatively unfamiliar to the gardening world, the restio family is almost entirely restricted to the Southern Hemisphere, occurring natively in Australia, Tasmania, New Zealand, Southeast Asia, Malaysia, Madagascar, Chile, and Africa. The family is comprised of approximately 38 genera and more than 400 species of perennial herbs, of which at least 300 are native to the Cape floral region of southern Africa. The climate in this region is Mediterranean, having cool, moist winters and hot, dry summers. The soils are typically sandy and very low in nutrients. The characteristic vegetation of the Cape is a fine scrub called fynbos, and in this restios often replace true grasses.

Closely related to the rushes, restios are most often, rush-like in appearance, although some have much-branched stems and bear a strong superficial resemblance to horsetails. They range in height from about 8 in (20 cm) to more than 10 ft (3 m). Restios rarely develop functional leaf blades. Photosynthesis takes place in the green stems, which may be solid or hollow, but usually have conspicuous nodes. Leaf sheaths are frequently present at the nodes and are often tan, gold, or cinnamon-brown colored and highly ornamental from a gardening perspective. Many restios are tufted and tussock-forming; others have slowly creeping rhizomes. Their roots may be fleshy or thin and wiry. The small, individual, wind-pollinated flowers are unisexual, with males and females occurring on separate plants. The flowers are green or brown in color and are typically grouped in spikelets, which in turn comprise loose inflorescences. Each spikelet is partly enclosed by a conspicuous, sheath-like bract that is often brown or amber-colored. Male and female plants of the same species are often quite different in appearance from one another, making identification and classification of this family more difficult than many.

The restio family is of no economic importance as a food source; however, a few species have long been important for thatching. Roofs thatched with Thamnochortus insignis, called dakriet in South Africa, may last more than twenty years, and a renewed interest in traditional architecture has led to a flourishing thatching industry in the African Cape. The beautiful stems and seed-heads of many restio family members are also important to the international cut-flower trade.

Many restios have great ornamental appeal, rivaling the graceful luminosity of the true grasses. Although few, if any, restios are winter-hardy in cold-temperate climates, they hold great ornamental promise for gardens throughout the world's Mediterranean regions and as subjects of glasshouse or warm-season container display. The reason restios are so little-known to horticulture has been, until recently, a difficulty in propagation. Restios do not like to have their roots disturbed and are ideally propagated by seed; however, germination rates for all but a few have been abysmally low using standard methods.

The cat-tail family

The cat-tail family is small, comprised of only one genus, Typha, and fewer than 15 species, yet it is commonly represented in freshwater habitats throughout the world. Herbaceous perennials, cat-tails prefer shallow water, growing to 8 ft (2.4 m) in height and spreading by rhizomes to form large colonies in swamps, ponds, and river and lake edges. They provide important nesting materials and cover for wetland birds.

Cat-tails are of minor economic importance; however, the mature leaves have been used for matting, thatching, and caning. The thick rhizomes are edible and high in starch, and are a potential food source. Native peoples have used the fluffy seed-heads as a substitute for down. The value of cat-tails as filtering agents in polluted wetlands areas is of increasing importance.