Tips on Caring for Ornamental Grass
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Ornamental grasses can play an important role in your garden design, providing an anchor with which to pull all the formal and informal elements of your garden into a synthesized whole. Their beauty lies in their linearity-the lines of their leaves, their stems and the branches of their flowerheads; and their motion-generally reaching a crescendo just as the rest of your garden is slipping into dormancy.
Grasses have not only beauty and variety, but also ease of cultivation. Given ordinary earth and a place in the sun, most are extraordinarily drought tolerant and need little care beyond an annual grooming.
Ornamental grasses would seem to be a perfect addition to the western garden, because of their ease of care, their drought tolerance, their winter beauty and the way they augment our already dynamic weather patterns.
Qualities of Grasses
Ornamental grasses can range in height from 1 foot to 14 or more feet and can be used for ground covers, erosion control, architectural features and screens. They make excellent companion plants due to the contrast they provide with traditional herbaceous perennials. Since grasses come in a variety of design forms—from tufted to upright to arching—you can certainly find a grass that will provide just the contrast you need to make your garden design come together.
It is important to recognize the different qualities of various grasses before planting them in your garden. Some grasses are rhizomatous, or "running" grasses, meaning they spread by underground stems. These grasses make excellent ground covers, provide erosion control and, due to the nature of their spreading, are naturally resistant to the invasion of weeds. But if they are heading where you don't want them to go, rhizomatous grasses give you the added hassle of vigilant spading.
It is important to recognize the different qualities of various grasses before planting them in your garden.
Keep in mind that not all rhizomatous grasses spread at the same rate—some advance as much as twelve feet a year in ideal circumstances. If you must have a grass with pernicious runners, you can plant it within an underground barrier, much the same way you keep mints in check. Other types of grasses form clumps that increase in circumference every year and require division every two to three years. Distinguishing between these two types of grasses will enable you to place them in an appropriate location in your garden and help to prevent headaches in future years.
Another variance in ornamental grasses is the distinction between warm and cool season grasses. Warm season grasses will grow and thrive during warmer times of the year and remain good looking even when temperatures are high and moisture is limited. These grasses do not begin to show growth until the weather becomes stable and the soils warm, and they usually do not require as frequent division as cool season grasses. Some warm season grasses include Japanese Silver Grass (Miscanthus), Hardy Pampas Grass (Erianthus) and Switch Grass (Panicum).
Cool season grass will start to grow early in the spring and may even remain semi-evergreen over the winter. These grasses also seem to do better and have better foliage quality when temperatures are cool or if they are given sufficient water during drought periods. If they are not watered during drought, they tend to go dormant resulting in brown foliage. These grasses may require more frequent division to keep them healthy-looking and vigorous. If not, they tend to die out in the center of their clumping form. Some of the more popular cool season grasses include Fescues, Blue Oat Grass (Helictotrichon), Tufted Hair Grass (Deschampia), and Autumn Moor Grass (Sesleria).
Caring for Your Grasses
All ornamental grasses must be trimmed at some point during the year. How and when you trim depends on the weather and the type of grasses they are. The best time to groom grasses is just after the winter, which will allow you to enjoy their beauty through those colder months. The warm season grasses will need to be cut back to within six inches of the ground, while the semi-evergreen grasses will need a trim in the spring-just snipping off the frayed ends and winter damage.
Nature's method of renewing grasses is fire, and were it not for the local fire codes and plastic irrigation equipment, the chore of ornamental grass garden cleanup would be a pyromaniac's dream. Use sharp shears to trim if you only have a few plants. A hard blade attachment on a weed whacker makes shorter work of more extensive plantings.
In fact, fertilizers high in nitrogen cause excess growth and weak stems...
As a rule of thumb, grasses should be fed lightly or not at all. Over-fed grasses tend to grow out of character, falling down when they should be standing upright. Generally, 1/4 the amount of fertilizer you feed your flowering plants is adequate. The exception would be bamboos which require a much richer soil and standard fertilizing practice. It is especially important to keep nitrogen levels low so that you don't have to be out staking your grasses when you want to be enjoying them for the low-maintenance beauties that they are. In fact, fertilizers high in nitrogen cause excess growth and weak stems so the usual neat habit is lost as the plants become floppy and unsightly.
In most gardens the biggest problem with ornamental grasses is that weed grasses may seed themselves into the crowns of desirable species. It is important to keep on top of this and not allow the weed species to become established.
- Miscanthus sinensis 'Silberfeder'—One of the most cold hardy and one of the earliest of the Miscanthus to bloom. Attractive display of silver flowering spikes beginning in August and nice red and gold fall foliage. Nice planted with Russian Sage and Purple Cone Flower.
- Schizachyrium scoparium 'The Blues'—The foliage on this cultivar is its outstanding feature. Bright blue in the summer and beautiful purplish fall coloration. Great planted with Sporobolis heterolepis and Sedum Autumn Joy
- Festuca idahoensis 'Siskiyou Blue'—it has superb blue-spruce blue coloration combined with a graceful habit and fine textured foliage. Very attractive in bloom as well. Great with Stachys Silver Carpet and Sedum Arthur Branch.
- Sporobolis heterolepis—This smaller growing prairie grass blooms with a haze of flowers in mid-to-late summer and has beautiful golden fall foliage. Should be mixed into the perennial border particularly with late summer, early fall blooming perennials like Salvia pitcheri Grandiflora, Liatris punctata, Echinacea purpurea, and Ratibida columnifera Yellow to name a few.
- Panicum virgatum 'Prairie Sky'—a robust, upright grower with very blue foliage and a nice display of fine textured flowers in late summer. Plant in the middle of a group of Artemisia Powis Castle.