Ornamental grasses haven't been so popular since the Victorian Age.
Dozens of ornamental grasses are now available, and new forms are
being added each year. The reasons for this astonishing rise in
popularity appear to center around the practical, as well as the
aesthetic merits of ornamental grasses. As the public becomes more
environmentally aware, and learns more about low maintenance plants
and sustainable landscapes, ornamental grasses that can tolerate
extremes of drought and wetness are eagerly sought. Many ornamental
grasses are also able to endure the repeated soil freezing and thawing
typical of northeastern winters. Ornamental grasses are also a part
of the growing popularity of water gardening, as transitional elements
between dry land and water.
grasses serve many functions in the landscape. Ornamental grass
foliage catches the wind, adding a sense of motion to the landscape.
The native prairies of the Midwest were often described as an inland
sea. Tall grasses also rustle in the wind, adding sound as a new
dimension to the landscape. In a border, grasses can be used as
edging or background plants, while larger specimens can be accent
plants or screens. Rhizome- and stolon-forming grasses stabilize
banks or serve as ground cover. Diminutive species can be utilized
in rock gardens. Combining
grasses with woody or herbaceous perennial plants, such as shrub
roses or Sedum 'Autumn Joy', help create a beautiful and enduring,
low input, sustainable landscape. The dried foliage and flowers
of many ornamental grasses are attractive and sway with the wind
thoughout the cold winter months. Many are excellent for use in
Ornamental grasses, in both foliage and inflorescence (seed head),
vary greatly in size, shape, color and texture. One of the largest
ornamental grass collections in the Northeast may be viewed at the
University of Rhode Island East Farm Agricultural Experiment Station
in Kingston. Call (401) 874-5220 to schedule a visit. Mature plants
range in height from 6 inches (blue sedge, Carex glauca)
to 14+ feet (hardy pampas, Saccharum ravennae). Grass forms
vary from low mounding to fountain shaped to tall vertical. Foliage
color includes shades of green, yellow, blue, red, brown and variegated
(green and white mixed). A number of grasses change in foliage color
in the fall, to displays of straw yellow, orange, red or purple,
providing a wealth of choices. Foliage texture varies from fine
to coarse (blade width from 1/8 to 1 inch). The inflorescence also
varies in size and color, and may change color in the fall as well.
a few grasses tolerate shade, most require full sun. Some grasses
or grasslike plants tolerate wet soils, but more require a well-drained
soil. To become drought and pest resistant, plants require a suitable
root zone. In compacted soils, even the root systems of the most
drought-tolerant plants will not develop. Incorporate organic matter
into the root zone to improve water-holding capacity and oxygen
levels. Adequate organic matter will develop a soil with sufficient
pore size to readily release water. The improved root zone will
allow for maximum root expansion and water extraction from the soil.
Improving the soil also will reduce irrigation frequency. Your investment
in soil improvement will be returned in fewer maintenance problems
and more attractive, longer-lived plants.
grasses may be propagated from seed or division, and can be purchased
from seed companies, mail-order firms and garden centers. Generally,
the improved strains, which include most of the new varieties, will
not come true from seed and must be propagated from divisions. Many
grasses do not transplant or propagate well after midsummer because
root growth slows dramatically. Container-grown plants may be transplanted
into the landscape throughout the growing season.
the foliage portion of the plant should be cut down to the ground
and removed each fall or spring, some fertilization is required
to compensate for nutrient loss. A 10-10-10 fertilizer may be applied
at a rate of 1 pound per 100 square feet. A good deal of calcium
and magnesium is lost when removing foliage, therefore a soil test
for deficiencies of these elements should be carried out periodically
and recommendations followed. Do not over-fertilize ornamental grasses,
as this can lead to lodging (falling over) and disease problems.
contrast to other flowering perennials, ornamental grasses require
minimum maintenance and most species are both insect and disease
resistant. However, improperly sited plants may become diseased
because of poor air movement, high nitrogen soils or inadequate
light. As ornamental grasses becomes more common, pest problems
may develop. At that point, cultivar selection will be more important.
As with most plants, there are common myths or misunderstandings
about the ornamental grasses. For example, many durable and hardy
ornamental grasses growing in Rhode Island are mistakenly called
Pampas grass. Cortaderia selloana, the only true Pampas grass,
will not grow in Rhode Island. Ordering grasses under the name of
Pampas grass will result in disappointment in this region.
grasses whose dried foliage is to remain for the winter near combustibles
such as a house or garage is not a wise practice. Dry grass foliage
and flowers can be highly flammable. Remove foliage in the fall
if a potential fire hazard is at all possible.
first question to ask about a grass: is it rhizomatous (spreading
by underground stems) or clump forming? Rhizomatous types make excellent
ground covers, erosion control plants, and dense cover plantings
that resist the invasion of weeds. The rhizomatous types spread
at different rates laterally, some as much as twelve or more feet
a year, and may be invasive. The clump formers simply increase in
circumference, requiring division every three or four years. Distinguishing
between the two types and locating them in proper sites will prevent
a great deal of difficulties in managing the garden, and results
in great satisfaction from this very desirable group of plants.
are many grass or grasslike plants suitable as ornamentals, both
native (ex. big bluestem, Andropogon gerardii) and exotic
(ex. fountaingrass, Pennisetum alopecuroides 'Hameln'). Native
grasses were members of the local flora before European settlers
arrived. Exotic grasses are introduced plants from other states
or countries. Some have escaped cultivation and become part of the
local flora. Some grasses, such as little bluestem, annual pennisetums,
and early flowering Miscanthus, can reseed in your garden or spread
to wetland areas where they can become real pests. New grass species
and cultivars should be evaluated for invasiveness before being
grown for sale.
The most popular groups of ornamental grasses are Festuca (fescue),
Miscanthus, Panicum (switchgrass) and Pennisetum (fountaingrass).
This cool season, clump-forming grass requires protection from
the hot afternoon sun. Blue foliage forms are the most popular.
Division in the early spring is often required to restore vigor.
Regular fertilization may benefit this group.
Considered the showiest group of warm season, clump-forming
grasses, it has very showy flowers. A large group of grasses with
considerable variability in height, blade width, etc. Select cultivars
carefully to insure adequate hardiness and adaptation to your site.
This native, warm-season, clump-forming group is becoming more
popular as new cultivars become available. Cultivars with red fall
color and blue foliaged upright cultivars are popular.
Most members are warm season, clump forming grasses. Some may become
weedy, especially south of Rhode Island. Both annual and perennial
cultivars are valuable in the landscape. Flowers are showy and are
foxtail-like in their appearance.
Brian Maynard, Sustainable Landscapes Program Department of Plant
Sciences, URI, Kingston, RI