How to Grow Ornamental Grasses

In the past few years, ornamental grasses have quickly gained popularity among gardeners. One reason is their incredible versatility. Not only do they add height, sound, movement, and visual appeal to garden landscapes, but they also thrive in less-than-ideal soil conditions and require only a minimal amount of maintenance.

Uses for Ornamental Grasses

Ornamental grasses can be used in a variety of ways:

• perennial borders

• ground covers

• specimen plants

• Containers plants

• cut/dried flower arrangements

• provide winter interest

• add an element of height, movement, and sound

• as shelter for wildlife

Selecting Grass Varieties

Depending on the growing zone, ornamental grasses can be considered herbaceous perennials or annuals. Before you select ornamental grass varieties for your garden, consider the height and spread of the species, what time of the year it's actively growing, (cool seasons or warm seasons) and its growth habits (forms clumps or rhizomes).

Cool season grasses: Cool season ornamental grasses start to grow early in the spring. They put on the most growth and look their best during the cooler temperatures of spring and fall. Because they are not as drought tolerant as warm season grasses, when summer temperatures start to climb cool season grasses go dormant and turn brown.

Once temperature cool, growth resumes. To keep cool season grasses looking good year after year, frequent division is necessary to prevent them from "dying-out" in the center. Examples of cool season grasses include Blue Oat Grass, Tufted Hair Grass, and Fescues.

Warm season grasses: Warm season ornamental grasses don't start to pour on the growth until the weather warms up. Once they get going, they are drought tolerant and maintain active growth even during hot and dry conditions. Unlike cool season grasses, warm season grasses do not require frequent division. To maintain their tidy appearance, cut warm season grasses back to a length of 4-6 inches in the spring. Examples of warm season grasses include Hardy Pampas Grass, Switch Grass and Japanese Silver Grass.

Clumping grasses: Clumping grasses form mounds or clumps. These types of grasses look great mixed in with perennials. They will not become invasive and take over your flowerbeds, but because they gradually grow larger (in diameter) over time, they require division every 2-3 years to keep them looking their best.

Running grasses: Runner grasses (rhizome-forming grasses) spread (sometimes aggressively) by way of underground stems called rhizomes. This growth habit makes them excellent candidates for ground covers, especially on slopes or uneven ground where it is difficult to mow. As ground covers, they help to stabilize soil and prevent erosion. If not being used as a ground cover, these grass types can easily be maintained in containers. When planted in beds and borders they will quickly grow out of control and overrun perennials.

Planting

Ornamental grasses can be planted in the spring or the fall. Gardeners in growing zones with cold winters should plant them in the spring so the plants have enough time to establish their roots before winter. Plant them at the same depth they were growing in nursery pots--any deeper and you will risk root rot.

Site: For the best color and greatest blooms, most varieties prefer a site with full sun (or at least 3-5 hours daily). A few species like Sedges, White Striped Ribbon Grass, and Northern Sea Oats tolerate partial shade.

Soil: Ornamental grasses tolerate a wide range of soil conditions. Light, well-drained soil are best, however certain species like Japanese Silver Grass and Switch Grass will grow well in moist, heavy soils.

Safety: Because grasses are highly flammable when dry, they should not be planted close to homes and other buildings where they can pose a fire hazard.

Watering

Regular watering is important, especially during the first year when plants are establishing root systems. In general, ornamental grasses are considered drought tolerant and do not need regular watering. The exception is some cool season grasses, which may require extra water to carry them through dry spells.

Fertilization

Unless growth lacks vigor and their appearance suggests otherwise, ornamental grasses don't require much (if any) fertilization. In fact, too much fertilizer (especially nitrogen) will actually result in floppy growth. If your soil is unusually poor or the grasses seem to be losing vigor, applying a slow-release balanced fertilizer (10-10-10) annually in the spring (1/2 cup per 100 square feet should be more than sufficient).

Propagation

Ornamental grasses can be propagated by seed or through division. Annual grasses are easily grown from seed, but division is the easiest and most convenient way to propagate perennials. (Hybrid grasses will not come true from seed and must be propagated this way.) Division should be done in the spring just as new growth begins, or in the late summer or fall after the growing season.

Winter Protection and Spring Clean Up

Ornamental grasses can be left uncut until spring. Not only does this provide winter interest in the garden as well as shelter to small animals, but leaving the dead, dried foliage helps supply the plant with nutrients when spring growth resumes. In the fall, add 3-4 inches of mulch around the base of the plants to protect roots from freezing. In early spring, cut dried foliage back to about 4-6 inches from the ground to expedite the start of new growth.