Ornamental grasses are valued in home landscapes for their hardiness and easy care, dramatic appearance and the wide variety of colors, textures and sizes available. Most ornamental grasses are perennials can return year after year. Annual grasses live for only one growing season, either because of their natural growth or because they are not hardy in our climate.
Ornamental grasses grow in either clumping mound or by spreading. Spreading grasses expand rapidly by aboveground or underground stems. They need to be thoughtfully planted and in appropriate places as they tend to become invasive, encroaching into other garden areas. Clumping varieties grow larger each season and form low mounds or fountains and tall verticals. Grasses vary in height with some forming a low groundcover and other reaching 10' or more.
Ornamental grasses are a year round feature in the garden. The flower heads of many grasses are very showy. Flowers and seed heads last for weeks or months, many providing interest through the winter. Foliage provides additional interest with a range of fine to coarse texture, softly arching or firmly upright form and deep green, blue, red or purple, yellow and variegated leaf color. Many grasses have good fall color, changing to yellow, orange, red or purple before fading to tan or straw for winter.
Through the summer taller species can serve as a wonderful backdrop to a perennial garden or can be used as quick growing screen or hedge. Smaller species can be placed among perennials in a flower garden. Grasses with striking form, color or flowers can be used as specimen plants. They can be used as groundcovers, for erosion control and as edgings.
Grasses also give interest to the garden in ways that few other plants can. They sway easily in the wind, adding the appeal of movement and rustling sound to the landscape.
Most ornamental grasses grow best when planted in well drained soil. Amending the soil down to 1 foot will allow them to grow in poor soils. Adding coarse textured organic mulch and compost to the soil will increase its drainage ability and add nutrients to the soil. Raised beds can be used to ensure good drainage as well. With a few exceptions, ornamental grasses need full sun. Some northern species will prefer some protection from the intense afternoon sun in the summer.
Planting ornamental grasses is similar to that of perennial flowers. If plants are pot-bound, loosen the roots around the bottom and sides of the root ball. Dig a hole at least twice, but preferably 3 to 5 times, the diameter of the root ball and just as deep. The wider the hole the easier it will be for new roots to grow and spread. Next, place the plant in the hole making sure that the top of the root ball meets the existing grade of the garden. Never plant grasses too low in the ground as it’s a major cause of premature decline in plants. Backfill around the roots with a mix of existing soil, peat moss and compost. Tamp the soil down lightly, water and let the soil settle. While many mature grasses are drought tolerant, they must have a well-established root system to withstand dry periods.
Once established, moisture needs vary by grass species, soil type and temperature. Most ornamental grasses will grow best with at least 1 inch of water per week from rain or irrigation. Soaker hoses and drip irrigation are the preferred methods of watering. They water deeply without wetting the foliage of a plant reducing the chance of foliar diseases.
Most ornamental grasses need very little fertilizer so base your application rate on a soil test. In fact, excessive nitrogen in the soil can lead to disease and and weak stems.
Since many grasses are attractive in the garden during winter, cutting back can be done in late winter or early spring. Cut stems to a few inches above ground level for best appearance. Grasses can be cut by hand with pruners or hedge shears. Gently rake through the foliage of ornamental grasses in spring to remove old leaves.
Most grasses should be divided every 3 to 4 years. If ornamental grasses are not divided, they eventually become thin or die out in the center. Dividing perennials is easily the best way to increase your plant stock. A few years after you've planted a perennial you'll probably notice that it begins outgrowing its allotted spot. Dividing overgrown ornamental grasses into smaller plants will solve the problem of over crowding in the garden while giving you new plants to add to other gardens. If you don't have space for any new plants, give some away to your friends. Simply dig the grass you intend to divide out of the ground, making sure to preserve as much of the root system as possible. Take a spade or a garden edger and chop or divide the plant in half. Remove any foliage which may have been severed. Separate and replant the vigorous growth on the outer edges of the clump back in the ground and back fill with a mix of compost and existing soil. You'll need some extra soil to fill in properly. Most grasses have very tough, vigorous root systems and may have to be divided with a shovel, saw or ax. Replant promptly, never letting the roots dry out.
Adding ornamental grasses to your gardens will provide movement, sound and year round features to your landscape. They're easy to plant and are virtually maintenance free. Experiment with various species and placement; they're quite versatile and can be used in almost any garden setting.