Monday, August 31, 2009

Ornamental Grasses – Easy Going and Easy Growing
by Steve Taylor, Blooming Nursery

Low Maintenance
Ornamental grasses are very low maintenance plants and should not be confused with high maintenance lawn grass! More time is spent maintaining a lawn than any other garden chore. It requires weekly mowing, frequent watering during dry periods, several fertilizer applications each year, plus weeding and edging when needed. But ornamental grasses only require sheering and fertilizing once a year, and occasional watering during drought. There are even some low growing Carex that make good lawn substitutes and require far less care than the more common lawn grasses.

Easy to Grow
Ornamental grasses are tough plants! Deer and other pests usually do not damage them. There is a long list of ornamental grasses that withstand subzero temperatures also. Most ornamental grasses are drought tolerant and not very particular about soil. Some will grow in swampy conditions and some will even grow in the shade. There is an ornamental grass for every kind of landscape site!

Design Considerations
From a design standpoint, ornamental grass provides a vertical element that provides contrast with perennials that are usually mound-shaped. Ornamental grasses are often used in between perennials of discordant colors, in order to blend them together harmoniously. They are also frequently used in container plantings as a centerpiece. Many ornamental grasses have the added bonus of providing color through their foliage. Many have leaves that are blue-green, burgundy, gold to chartreuse or are brightly variegated. Although grasses do not have flower petals, some, such as Miscanthus and Pennisetums, have a very showy inflorescence nonetheless.

Ornamental grasses surpass all other garden plants for creating effects with back lighting. The flowers and foliage are highly translucent and are most dramatic early in the morning and late in the day when backlit or side-lit by the sun. Grasses also move gracefully in the wind, often creating a rustling sound in the breeze.

Clumpers vs. Spreaders
The vast majority of ornamental grasses do not spread. There are some notable exceptions however. You may want to avoid planting the following spreading grasses, especially if you have moist soil: Typha (Cat-tail), Phragmites australis (Common Reed), Phalaris arundinacea, Arundo donax (in California), Miscanthus (in southeast US.) and Imperata (in subtropical US). Although locally (in the Northwest) we have not seen problems with Miscanthus nor Imperata, the potential for invasive behavior exists. Running bamboo like Pleioblastus and Phyllostachys can also be invasive, however some bamboos, like Fargesia are clump forming. A few ornamental grasses can self-sow aggressively, examples are Helictotrichon, Pennisetum ‘Little Bunny’, Pennisetum ‘Moudry’ and Chasmanthium latifolium, but it is easy to control this by cutting off the blooms before they form seed. In spite of these exceptions, most ornamental grasses can be used in most landscapes without concerns that they may take over or damage the native habitat.

Warm Season Grasses and Cool Season Grasses
Grasses are usually grouped as either warm season growers or cool season growers. Cool season grasses grow best from 40 to 75 degrees, provided they have ample moisture. Examples are Deschampsia, Festuca, and Helictotrichon. Cool season grasses will go dormant in summer during periods of high heat and drought. When dormant, cool season grasses will turn brown. Even though dormant, it is still necessary to water about 1 inch of water per month to keep the roots of cool season grasses alive. Warm season grasses grow well from 75 to 95 degrees, again with ample moisture. Warm season grasses typically break winter dormancy late in the spring and are slow growing until summer arrives. Most warm season grasses bloom at the end of summer. Examples are Miscanthus, Panicums and Pennisetums.

A Few Common Ornamental Grasses
Carex is technically a sedge, rather than a grass and has over 1000 species within the genus. Many have striking foliage and all combine well with perennials. Most ornamental sedges originate from moist or wetland habitats in temperate regions of the world. The sedge flower is usually not important for ornamental purposes, but the foliage colors exceed the diversity found in other grasses. Bold variegations, blue-green, yellow, brown and orange foliage colors are common among Carex and many are evergreen as well. Some form clumps, others are spread by runners. Some sedges are being used for drought tolerant, low maintenance lawn substitutes.

Cortaderia is one of the most dramatic of all ornamental grasses for its feathery plumes. The flower stalks are held erect above the foliage in late summer and early autumn and remain attractive into winter. This grass can often reach 12-15 feet tall, although smaller growing cultivars are available. It can be quite drought tolerant once established.

Deschampsia is a superb ornamental grass, native to the Pacific Northwest. It is valued for its neat, dark, evergreen foliage and for the ethereal cloud-like quality of its inflorescence, which has a hair-like texture and the common name of Hair Grass. It prefers moist soil in sunny locations and grows best when temperatures are cool. The foliage grows 1-2 feet tall. The flowers bloom in midsummer and can stand 3-4 feet tall above the foliage.

Festuca or Fescue usually forms short tufts of blue-green foliage that look perfect in rock gardens. They are cool-season growers and often go dormant during hot and dry summer periods.

Hakonechloa has arching foliage that will slowly spread to form a groundcover, although it is never invasive. It is a warm season grass, but prefers to grow in moist shade. The yellow variegated form ‘Aureola’ is the 2009 Perennial Plant of the year. The chartreuse foliage is excellent for brightening shade when contrasted with Hostas and ferns.

Helictotrichon is a western Mediterranean native. It forms tufts of erect, silver-blue foliage to 2.5 feet. A cool season grass, it will go dormant and turn tan in hot dry weather, but it is well adapted to the dry summers of the Pacific Northwest.

Miscanthus is unrivaled in the exotic beauty of its flowers, foliage, autumn colors and winter presence. It is extraordinarily adaptable to many conditions and purposes in the garden. Being warm season grasses, Miscanthus starts to grow rather late in the spring, but they grow quite strongly in the heat of summer. They grow well in most soils and can tolerate marshy conditions. The showy luminescent plumes in late summer are usually silver to white. It is superb for creating exotic, tropical effects in the garden.

Nassella is native to dry fields in the south central United States. It produces a dense green fountain of hair-like leaves ending in silvery inflorescence that bloom from June to September. A cool season grower, the blooms will turn straw colored during hot and dry summers, although it is also very drought tolerant. It self sows readily, but usually is easily controlled.

Panicums are native to the prairies and open ground in eastern North America. It was once a major component of the tall grass prairie. A warm season grass, it thrives in hot humid weather. Many have blue-green foliage that grows 5-7 feet tall. The inflorescences create an open and airy texture in the garden.

Pennisetum has the common name of Fountain grass, as these grasses have inflorescence with a fountain-like appearance. There are many species of Pennisetum from both temperate and tropical regions. Pennisetums are warm season grasses that vary in height from just 8” tall to 6’ tall. All have feathery inflorescence, somewhat like a foxtail. These feathery bottlebrush flowers arise in late summer to fall and range from coppery bronze to deep purple. Plants grow well on almost any site and only require full sun to be at their best.

Room for More
Ornamental grasses are widely used for commercial sites, but they are still underused for residential landscapes. Take another look at your garden to see where these low maintenance landscape workhorses can add beauty and grace. The possibilities are endless!

For more information and to see photos of the grasses described in this article please go to and click on the "plant finder" icon on the left side of the screen. You can browse hundreds of grasses and find retailers near you where you can purchase grasses and other perennials grown

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