Growing Ornamental Grasses

Most grasses are best planted in early spring so they will be established before the heat of summer. In addition, a better selection of grasses is usually available in the spring. In mild or southern climates, grasses can be planted year-round. Container-grown grasses can be planted in summer as long as adequate moisture or shading is provided to allow plants to get established.

Cool-season grasses can be planted in the fall, and they enjoy the early start. Though top growth may be marginal, fall plantings let roots become established prior to spring's burst of growth. This pays off with stronger, faster-growing plants in the spring. Fall planting carries the risk of winterkill. Protect new plantings from desiccating winter winds and keep them adequately moist to prevent the plants from drying out. Late fall plantings of some grasses may require winter protection. To be safe, plant early in the fall.

Planting in the summer can be risky, because heat spells can catch new grasses before they have had enough time to establish. Cut the foliage back by one-fourth to one-third when you plant in hot summer, to prevent foliage damage until plants are established. New foliage is quick to return. During heat spells, plants may need constant moisture to avoid drying out.

Seeding grasses directly in the garden is best done in early spring, so the plants can become established before the heat of summer. Summer seeding is possible, but new plantings may require constant attention and watering, and you may need to overseed bare spots. Fall and winter seedings are slow to establish and are usually not advised, though in mild climates some grasses do just fine.

Soil

Most grasses aren't fussy at all. They require little or no soil preparation or special care. This does not mean that plants do not grow better in improved soils. Most grasses readily reward any improvements with increased vigor and growth.

In general, grasses appreciate a soil rich in organic matter. But you must strike a balance between adequate care and over stimulation. Too much nitrogen may contribute to weak, floppy foliage, and a lowered resistance to insects and disease. Give your grasses an extra boost of nitrogen by applying well-rotted manure or compost. But once new grasses are established, cut down on fertilizers and let them adapt to a leaner soil.

Grasses are quick to adapt to their existing soils, so traditional soil preparation is often unnecessary. In some circumstances, special soil preparation is required for good growth. The art of garden-making lets you modify the soil, so you can grow almost any plant. More basic improvements are sometimes necessary, too. Grasses requiring good drainage, such as alpine grasses, benefit from the addition of sand or gravel. In many hot southern climates and southern clay soils, good drainage is essential to prevent rot in cool-season grasses that are more at home farther north.

Eliminating noxious grasses

The worst enemy of an ornamental grass planting is a noxious perennial grass. Bermuda grass (Cynodon dactylon) is one of the worst weeds in an ornamental grass planting, and Quack grass (Agropyron repens) often plagues gardeners.

Eliminate perennial pest grasses long before planting. Organic control of running grasses can be difficult. Hand-pull as much of the pest grass as you can. Be sure to remove any broken bits of roots or stolons, which can re-root. Take your time and do a thorough job. When you are sure all the grass is removed, loosen the planting area with a garden fork and water the soil well. Wait two weeks for the pieces of grass you missed to rejuvenate and sprout. Weed out all traces, then let the prepared area sit for another two to four weeks to make sure all noxious grass is gone. In the event of severe infestations, it may be nearly impossible to eradicate an undesirable grass. This is often solved by planting a more aggressive, taller grass that will shade out and dominate the lower weedy grass.

Spacing

Determining the spacing of grass plantings can be a function of several factors: budget, aesthetics, and how fast you need cover. Spacing is more often a matter of personal taste than of rules. There is no real right or wrong. Spacing clumping grasses farther apart gives a hummocky look preferred by some gardeners. Others like closer spacing, which creates a massing effect. As a general rule, place plants as far apart as their eventual height. Grasses that mature at 3 feet tall, for instance, may be planted 3 feet apart from center to center. On slopes or where a quick cover is desired, plant closer to help hold a steep bank or grade.

One of the most common mistakes to avoid when planting ornamental grasses is failing to realize just how big a plant will grow. Another common error is planting large grasses too close to a walkway. Remember to keep the eventual girth of the plant in mind. Close spacing is a luxury that requires a large budget. If your budget is limited, it will just take a little more time for your planting to fill in.

Planting

Planting grasses is a relatively easy process; you just need to apply the same principles used in planting any perennial garden. Keep these guidelines in mind when planting grasses.

• Always try to match the original soil line of the plant.
• Avoid planting too high or too low below the crown. Many grasses, especially when small, will not tolerate being planted too deep.
• Water newly planted grasses immediately, and remember that newly planted grasses are particularly susceptible to drying out. On a hot summer day, young grass plants that have not been properly watered and are exposed to the sun can be killed in less than an hour.

Mulching

Once your newly planted grass has been watered deeply, mulch it to get it off to the best possible start. Mulching is an important step in ornamental grass gardening. It cools the surface temperature of the soil in hot climates, preserves moisture, keeps down weeds, and provides necessary soil nutrients. Mulching also provides a measure of winter protection, insulating both plant and soil. And a mulched surface provides an attractive backdrop while newly planted grasses are filling in. Wood chips, bark, compost, leaves, and grass clippings all make suitable mulches. Most grasses grow better with a 2- to 3-inch layer of mulch over the soil surface.