Winter and early spring are the best times to divide ornamental grasses.
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Dry winds of autumn ruffle golden fields of grass. The winds whip the seed heads and blades into waves as animated as any seascape. But grasses carry on a far more intimate relationship with wind than you might imagine. They reproduce by harnessing the wind to carry pollen across field and prairie for a new generation of seed.
All plants must flower in order to reproduce, and grasses are no exception. Their flowers are known as inflorences, which are composed of many individual, rather inconspicuous flowers or spikelets that contain both sexes. There is no color because they do not need to attract bees or other insects to pollinate.
With the wind as pollen vector, gasses must send their flowers high above the foliage to obtain full exposure. This explains why the inflorences, so open and airy, are so suited to work with the wind.
After pollination, these same spikes will hold the seed like a staff of wheat or barley. When seeds mature they loosen and again the wind picks them up and carries them far from the mother plant. It is just this windborne travel that makes grass the most common and universal plant on Earth.
The beauty of ornamental grasses is most apparent in the fall when the inflorences are large and full of seed. The great fluffy heads of Pampas grass are so outstanding they are sold as interior decorations. Even as the grass blades die back to gold or sepia at season's end, the strong flower stalks remain. Those with good structure will maintain their beauty under the early snow, adding form and color to winter. The lingering seeds are a favorite forage of winter or migratory birds.
As cold and wet beats the plants down they will disappear through the darkest of days, often flattened under heavy snow. Yet in the early days of spring they are revealed again, and it is time to remove the tattered remnants of the previous year.
Ornamental grasses are perennial plants. Like daylilies or phlox, they will rise up from the same root crown each spring. Grasses grow from a root crown or tussock that sits just at or below the soil. It is a mass of tussocks that created the famous American prairie sod so dense it was used to build houses. Each year this dense fibrous material generates new blades and stems. The root crown gradually expands with time, increasing the overall diameter and lushness of the plant.
Over time grasses can become old and decadent. New growth occurs on the outside edges, causing the center to die out. When you find an unsightly hole ringed by fresh growth you'll know it's time to divide and renew the grass.
You can divide them in winter or early spring before growth begins. This involves lifting the tussock with a spading fork. Then discard the dead center and divide the remainder into sizeable chunks. You can use a spade, knife or narrow trowel for this. Make each chunk large enough to contain at least two growing points. Replant in ground or in pots to create many identical clones of its parent.
For an excellent guide to ornamental grasses and their care, Rick Darke's Color Encyclopedia of Ornamental Grasses (Timber Press, 1999) remains the best book on the subject. Fabulously illustrated, it takes the guesswork out of selecting and caring for these beautiful plants.
With a clearer understanding of how the annual dances of wind and grass sustains these species, everything about the plants makes sense. Soft and yielding yet cold hardy and tenacious, few plants can stand up to their beauty. And if you walk in the country where the dry grass rustles on golden autumn afternoons, you may hear them out there chattering away. It is a sound that touches a primal chord in all of us, evoking that momentous time when we hunter / gatherers finally evolved into growers.