Trimming ornamental grasses

There is no doubt that ornamental grasses are frequently planted because of their shimmering beauty, but there's also no doubt that their low maintenance endears them as well. For those gardeners who've been admiring their grasses all year without lifting a finger, now's the time to undertake a once-annual maintenance chore. Start by gathering gear and setting out a schedule for shearing them back.

An ideal scenario would feature straight stems holding faded flower heads sturdily upright, but recent winds and rains have had their way, beating down grasses and leaving us with a messy clean-up.

Given the vagaries of the weather, trimming is ultimately a matter of timing and convenience, different for each location. In many cases, grasses are an integral part of the late-season garden. Cutting them to the ground--or 4 to 6 inches above--completely destroys that value. But when clumps collapse and are blown hither and yon, the task is surely at hand, requiring a rake and some patience in collecting strewn pieces.

The type of grass and extent of wind and rain damage are the first considerations in determining when to prune. Some species, such as tall silver grass (Miscanthus), lose their arching foliage to breakage but retain tall inner stems holding flower heads. These are quite lovely covered with morning dew and even more beautiful painted with a layer of glittery frost.

In colder climates, grasses take on a dramatic look capped with snow and are left standing as one of the very few points of interest in the winter garden. But in our relatively mild climate, we have so many other plants that hold the garden together during these cold months that we need not rely as much on grasses. Besides, they rarely bear a snowy mantle.

The risk of waiting too long becomes clear as the weeks roll by. While grasses lie dormant to our eyes, roots become active. Suddenly, before we realize it, spring is here and new growth is well under way within dry clumps not yet trimmed. Had we had pruned weeks earlier, we would be looking at attractive, fresh green mounds. All that new growth is damaged, however, and will be sheared off with delayed pruning.

It should be noted that evergreen species require trimming only every few years. These include giant feather grass (Stipa gigantia), deer grass (Muhlenbergia rigens), bamboo muhly (M. dumosa), and Miscanthus transmorrisonensis.

Trimming options

Quite a few methods work equally well in cutting back ornamental grasses. It may take a little experimentation to find the one easiest for you. Very tall species with thick stems are best cut aggressively with heavier tools while low-growing types are easier to manage with smaller ones.

Hand pruners. It takes strong hands and wrists and a little more time to make cuts when you rely on this method. It also calls for a sharp, good quality tool, such as Felco brand. Hand pruning is best reserved for thin, delicate grasses such as fescues and small, young clumps of taller species such as fountain grass (Pennisetum orientale).

Loppers. These work on nearly any grass, but can be awkward to manage. They cut through thick stems with ease, if only a few at a time. Loppers might be the tool of choice when your options are limited.

Hedge shears. Long-bladed hand shears are somewhat awkward for trimming low to the ground, but electric hedge trimmers are one of the most popular tools for a fast, clean sweep.

Grass clipper. Craftsman and Black & Decker are two manufacturers who put out a rechargeable, hand-held clipper variously called a combo clipper or grass trimmer. The scissors action makes fast work cutting grasses and other plants with thin stems.

Bow saw. Although it is designed for cutting limbs and logs, this saw can be useful on large clumps of tough grasses.

Lawn mower. Some natives, including evergreen deer grass, benefit from having all above-ground growth removed every few years. Burning in other areas of the country accomplishes this on dry dormant species but is not recommended here. A lawn mower is a better option.

Safety first

Always wear gloves whether you use hand pruners or a power tool. It's amazing how our hands manage to find their way to the cutting edge as we hold stems at the most manageable position. Gloves are needed also when handling grasses such as Miscanthus with sharp leaf margins.

Wearing goggles is equally important to protect eyes from flying shards of dry grass.

If you're tempted to get out a chain saw, think twice. Its power is literally overkill for grasses in home gardens and for home gardeners ourselves, no matter what our experience may be cutting wood. Grasses are not wood.

The same goes for string trimmers. The string action disperses grass wildly without giving a clean cut. The metal attachment is far too dangerous.

Rosemary McCreary, a Sonoma County gardener, gardening teacher and author, writes the weekly Homegrown column for The Press Democrat. Write to her at P.O. Box 910, Santa Rosa, 95402; or send fax to 521-5343.