The Life Of Grasses

When a grass is left uncut, unmowed, and untouched, it becomes a plant entirely different from the grass that makes up the familiar lawn. The great majority of grasses are easy to grow and quick to bloom when liberated from constant mowing or grazing.

Most grasses are capable of growing to their mature size in one or two seasons. Mature can mean 12 inches tall, as in the case of large blue hairgrass (Koeleria glauca), or 12 feet tall, as in the case of giant Chinese silver grass (Miscanthus giganteus). Pampas grass (Cortaderia selloana) shoots up so fast that on a hot summer day you can hear the plant growing. Sugarcane (Saccharum officinarum) grows at a rate that exceeds that of most plants because it has accelerated photosynthetic abilities. In fact, many grasses have this ability; given ideal conditions they will take their place quickly in the garden. From a seedling or a small plantlet, grasses begin to produce roots, shoots, and leaves.

Leaf and stem

Grass leaves-fine and wiry, flat and broad, folded, curly, or anything in between-fill our gardens with texture and motion. But all those shapes have a practical side, too, evolved in response to climate and conditions. Rolled or folded leaves, for instance, slow down the evaporation of water and are often found on grass species from dry areas. Razor-sharp edges and wickedly pointed tips help protect grasses from foraging animals.

The foliage of ornamental grasses comes in every shade of green, from lime to dark forest green, and in colors of red, yellow, blue, purple, and brown. Some species are soft and downy to the touch, others are shiny or pleated, and some can slice skin like a razor. Grasses that are spotted or striped with white or yellow add a feeling of light and movement.

The stem of a grass, called the culm, bears leaves, flowers, and seeds. Culms vary from thin and flexible to woody and rigid. Leaves form on the culm, and flowers are borne at the top of it.

Culm and leaf arrangements differ from grass to grass. In tufted and mounded forms, culms remain hidden at the base of the grass, becoming visible only when flower spikes begin to emerge. The culms of upright-growing grasses are often a visible and noticeable part of the plant throughout the growing season. Grass culms are usually similar in color to the foliage, but these stems can have contrasting colors. 'Pele's Smoke' sugarcane (Saccharum officinarum 'Pele's Smoke') has polished burgundy red canes and translucent purple leaves.

Many sedges and rushes appear identical to true grasses, but others have a completely different arrangement of culms and leaves. Some members of the sedge family (Cyperaceae) form tubular stems with greatly reduced leaves. A good example is Egyptian papyrus (Cyperus papyrus), which has bare stems 6 to 9 feet tall, topped with a large umbel-like cluster of drooping leaves, up to 2 feet wide. The culms of rushes, members of the Juncaceae family, are almost always cylindrical, and leaves are greatly reduced or absent. But woodrushes (Luzula spp.) have grasslike leaves and flowering stems, and look more like sedges or true grasses.

Flowers and seed heads

What most people refer to as a grass's flower is in fact an inflorescence, a group of flowers. Each tiny, individual flower, held in a structure called a spikelet, remains hidden until flowering time. Grass inflorescences have three basic forms: spike, raceme, or panicle. A spike is the simplest arrangement: the individual flowers are attached directly to the main stem, with no branches. In a raceme, the spikelets are held on branches directly attached to the main stem. A panicle is the most complex arrangement, bearing spikelets on branches or stalks off a main stem. A panicle may include flowers arranged in racemes on its branches. The flowers on spike, raceme, or panicle may be arranged loosely, giving an open, airy feel, or they can be dense or even one-sided.

Spikelets usually emerge one-color; then mature to another color. On newly emerging inflorescences, spikelets can be shades of green, red, pink, silver, or bronze. As they mature, they mellow to tan, gray, gold, and brown. Some spikelets appear hairy or bristly, thanks to a pronounced needlelike awn that extends from the spikelet. The silky awns of feather grass (Stipa spp.) capture the light and sway in the slightest breeze.

When grasses go to seed, the flowers often take on a completely different form and color. The silky plumes of maiden grass (Miscanthus spp.), red, purple, or white on emergence, become fluffy and puff up like cotton candy, maturing to creamy tan or brown whisklike plumes. Grass seeds are usually dispersed by the wind and fall to the ground. Light seeds may float in the breeze. After the seeds have dispersed, flower heads usually remain erect until wind, rain, or snow knock them to the ground. Often, these old flower spikes remain decorative in the garden through the winter. The vast majority of grasses bloom May through July. However, there are grasses that bloom into November, and some that bloom in winter.

Fall, winter, and spring again

As fall approaches and the days become shorter, grasses again begin to change. Warm-season grasses now assume their autumn colors. By late fall, their colors are blanched to the soft hues of winter. Next year's growth, the living buds, lie dormant at the crown of the plant, ready to emerge with the coming of spring. Cool-season grasses begin to grow again in fall, long after flowering.

In late winter or spring, depending on the grass, new shoots begin to emerge through the dried remnants of last year's growth. In gardens, we often cut grass back to keep the plantings tidy. In nature, grasses grow up through last year's growth until they have grown past this old growth, which has begun to decompose. With the emergence of new growth, the cycle has come full circle and another season is under way.