Ornamental Grasses

10/8/05

Ornamental grasses are growing in popularity all over the country.  Today's nurseries offer a wide variety of sizes, shapes, and colors compared to 30 years ago when pampas grass was the standard.  Now there are grasses to suit any site in a range of sizes from six inches to ten feet.

Grasses are attractive throughout the growing season but many put on a show during the fall.  The foliage of many grasses change color as daylength gets shorter and temperatures cool.  Seed heads also develop in summer to early fall, often changing color with the seasons.

Design Tips

When using ornamental grasses, plant in groups.   The size of the landscape and the mature plant size will dictate how many to install.  Low weeping grasses like muhly grass look great planted in mass to create large sweeping drifts of color.  Larger maturing varieties are sometimes used to create a color or texture change as an individual accent plant. 

Try including them in a perennial bed for a texture change.  Taller varieties can be used to create a screen or backdrop whereas smaller ones work well as a border.  Others look great in containers especially when mixed with a trailing flowering annual.

Grasses add a lot of character to a landscape because of the various textures and colors.  They also add motion to a landscape because they respond to the slightest breeze.  Many of the new varieties are chosen because of the added bonus of colorful flowers.  Some grasses are very stiff and upright whereas others have a soft, weeping growth habit.

Before selecting a grass for the landscape, find out the plants mature size and whether the grass is deciduous or evergreen.  Deciduous grasses die back during the winter months, changing to various colors before retiring to a straw color.  Depending on the location, the deciduous grasses might be displayed with evergreen plants to maintain color during the winter months.

Match the grass to the site as some have high moisture requirements whereas others prefer dry sites.  Some may become invasive by either reseeding or spreading by runners into adjacent areas.  Grasses are divided into 2 growth categories, clumpers and spreaders.  Clumpers expand in size every year by forming new divisions but stay in the general area.  Grasses that are runners spread by underground rhizomes and creep in many different directions.  These are often used as ground covers and are very effective in stabilizing an area to prevent erosion.

Notable Varieties

One group that is favored for their flowers is the Pennisetums.  There are over 100 species but there are several favorites.  Fountain grass, Pennisetum alopecuroides, is a deciduous clump-forming grass that has been popular for years.  It is a dense upright plant that matures at 2' to 4' with a matching width.  Four to ten inch long foxtail flowers appear above the foliage in early summer to mid-fall.  Leaves turn golden yellow in the fall. This one has a habit of reseeding and moves around the garden at will.  Other named varieties of this species include Hameln, Little Bunny, Cassian', and Moudry. 'Cassian' is slightly smaller maturing at two feet extending to three feet when flowering.  It's loaded with four inch whitish-tan foxtail plumes.  Foliage color changes from green to yellow with red tinges as weather cools.

Oriental fountain grass, Pennisetum orientale, is a beautiful low growing deciduous plant maturing at 12" to 18".  Showy pink-violet flower spikes arch out 12" to 16" above the foliage.  It has a clumping growth habit with blue-green foliage and is considered by many to be the prettiest of the fountain grasses.  This is a good selection to include in perennial beds, as a border, in mass plantings, or for container gardens.  One improved variety is 'Karley Rose' with rose-pink flowers maturing at two to three feet.

Maiden grass or Miscanthus is another popular group that includes over 20 species and 50 plus cultivars.  Japanese silver grass, Miscanthus sinensis, is a perennial clump-forming grass that makes an attractive background, hedge or screen.  The middle of the leaf blade has a silver stripe that runs the entire length of the blade.  Depending on the cultivar, height varies from 3' to 12'.

One of the best Japanese silver grasses for our area is 'Adagio'.  Rust disease is a common problem but 'Adagio' is resistant.  'Adagio' is a compact variety maturing at four to five feet tall with narrow silver-gray leaves.  Pink flowers form in the summer and turn white as they age.  Leaves develop a yellow fall color.  Plant in full sun or partial shade in a well-drained soil.  Other varieties include 'Cosmopolitan' maturing at a stately nine feet tall with green and white striped leaves and attractive red flowers, 'Graziella' toping out at five to six feet with yellow flowers and foliage that turns red orange in the fall, or 'Morning Light' maturing at three to five feet with white edged variegated leaves and reddish bronze blooms in the fall.

Muhly grass, Muhlenbergia capillaris, is by far one of my favorite native grasses.  Leaves are 2' to 3' long, blue-green to gray-green, and are very narrow, almost threadlike.  Leaves arch to form a compact mound.  It's most noticeable when in bloom because it's covered with a blur of pink to purple flowers from October through November and is best displayed in mass.  These are tough plant that will grow in hot, dry sandy soils and are very drought tolerant once established.  Plant in full sun to light shade.

Switch grasses, Panicum virgatum, is native to North America and will tolerate sun to partial shade and dry to moist soils.  Switch grass matures at four to seven feet and produces yellow fall color.  Check out the popular 'Heavy Metal' maturing at five feet with bluish upright leaves.  Other examples include 'Dallas Blues' with wide blue foliage and soft pink seed heads, 'Cloud Nine' with upright blue-green leaves that turn yellow in fall, and 'Shenandoah' with green leaves that turn red by mid summer.  Switch grasses are also salt tolerant making them good candidates for coastal areas.

Another native grass that is striking in the landscape is love grass, Eragrostic spp.  Two popular selections include weeping love grass, E. curvula and purple love grass, E. spectabilis.  Weeping love grass matures at three feet with a lavender-gray flower head that bends and droops to the ground.  Purple love grass matures at 1' to 2' with reddish-purple fall flowers.  They are spectacular when in bloom because their flowers are so fine, they create a cloud of color.  Both will tolerate poor soils and are very drought tolerant.

Carex is a grass-like plant that is great in moist locations.  Carex may look like a grass but is classified as a sedge.  One that is growing in our demonstration garden that has color year-round is Carex phyllocephala 'Sparkler'.  Plants mature at fifteen inches tall and leaves are creamy white with a green stripe down the center.  Leaves have an unusual growth habit and resemble small palm trees.

Check local nurseries for availability but you may have to surf the web to find the more unusual varieties.

By Terry Brite DelValle, Duval County Environmental Horticulture Extension Agent

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