The Silent Invaders

Like all invasive plants, they blend into a world of green vegetation which the ordinary passerby considers "a good thing". The most silent of the invasive plants in this scene are the exotic grasses. The grasses spreading quietly across the landscape often are unnoticed because all grasses look alike at first glimpse, until they flower. Grasses are simply difficult to identify, flowering or not. You have already heard of weedy Cheat grass, Johnson Grass, Medusahead rye and Smooth brome. Here are ten other grasses, you should get to know. Some have infiltrated the West and some have blended into the East; but all are spreading across the nation. Some State Departments of Transportation are planting one or two of these, but most are trying to eradicate them. Here are ten grasses to learn about and watch for!!!

	Chinese Silver Grass, Miscanthus sinensi. This grass originates in eastern Asia and has become a popular ornamental grass. It has escaped easily into highway corridors, woodland borders and wetland edges. This 4-8' perennial spreads by rhizomes and is on a number of "watch" lists. IT is easily recognized in lathe autumn by its silvery plume-like panicles. It has been observed as far West as Minnesota.
	Reed Canary Grass, Phalaris arundinacea. This 3-7' perennial came from Europe and Asia. It was introduced for its forage value and later planted for erosions control and naturalized. It grows in dense mats and spreads vegetatively and tolerates dry to wet soils. Unfortunately, it is said that a native species exists and the distinction between it and the exotic is complex. Because the Eurasian species crowds out native habitats, it is best not to plant the available commercial seed. This invasive wetland grass is abundant from coast to coast.
	Giant Phragmites or Common Reed, Phragmites australis. You cannot miss this 10-15' perennial. It spreads by seed and by rhizomatous runners and can reach 10 or more feet in a single season. It threatens wetland communities, changes hydrology, alters wildlife habitat and increases fire potential. This grass is often confused with a native, shorter, Phragmites that is a natural component of many undisturbed tidal and freshwater marshes. The robust Phragmites found in ditches and disturbed wetlands is likely the invasive. This grass was introduced on the Atlantic Coast in the 1900's.
	Giant Reed, Arundo donax. Known as giant reed because it can top 20', this perennial has creeping rootstocks and deep fibrous roots. This grass prefers moist places and tolerates saline soils as well as heavy clays and sands. It is thought to have been introduced from India in California in the early 1800's. it was widely planted as an ornamental and for erosion control. Historically this grass was used for basketry, woodwind instruments, fishing rods, etc. Primarily, it spreads vegetatively.
	Fountain Grass, Pennisetum setaceum comes from northern Africa. It is a small (2-3') perennial grass which grows in clumps. Its bristly, purplish inflorescences are attractive. This grass is a poor pasture grass and a serious weed in dry habitats. This grass not only tolerates droughty conditions, but a wide elevational range. In Hawaii it establishes on rangelands to bare lava flows. It is a wind-dispersed seeder and seeds remain viable six years or longer. Not only is this grass aggressive in natural communities, but it also raises fuel loads increasing the spread of wildfires.
	Cogongrass, Imperata cylindrical. Cogongrass came from Southeast Asia. This perennial is rhizomatous and grows from 2-4' in height. The leaves are an inch wide with a prominent white midrib, ending in a sharp point. Cogongrass can invade and overtake disturbed ecosystems. Recent hurricanes in the South could speed up their spread. The grass is a threat to habitat and endangered species. It is tolerant of shade, salinity, and drought. It was accidentally introduced in Mobile, Alabama via packing materials. It was also introduced as forage grass and erosion control and is still sold as an ornamental grass. It is considered one of the world's worst weeds and is on the Federal Noxious Weed List.
	Buffelgrass, Pennisetum ciliaris. Buffelgrass is one of the most common invited species turned invasive. The grass increases grass cover and the possibility of man-made fires. It is an perennial African bunch grass. It was introduced in the 30's for erosion control and forage. From there it was sold to ranchers in Sonora, Mexico. Only salinity, clay, and poor drainage limit it. This grass now threatens the entire Sonoran Desert Bioregion on both sides of the border. For more information, read "Drought-Tolerant Exotic Buffel-Grass and Desertification" by Alejandro E. Castellanos-V, et. al. in the 2002 Weeds Across Borders proceedings.
	Japanese stiltgrass, Microstegium vimineum. Originally from Asia, this is an annual grass that averages 3' in height. It grows in a branching, sprawling, mat-like manner. Its pale green leaves are alternate along a branched stalk,stalk, resembling a small, delicate bamboo. A easy characteristic to catch is a pale, silvery stripe of hairs along the midrib of the upper leaf surface. The flower spikes appear in September and go to seed by early October. The grass tolerated shady and moist environments. Typical habitats invaded by stiltgrass include forested wetlands, moist forests, old fields, rights-of-way, and river corridors. It is now found in most Eastern States.
	Pampas Grass, Cortaderia selloana is a perennial clump grass from South America. Pampas grass has light violet to silvery white plumes. Its cousin, Jubata grass, Cortaderia jubata, Its brownish or purplish plumes are might taller. Jubata flowers in late summer, long after Pamapas grass. It has been used both as erosion control and as an ornamental. Because it establishes rapidly on bare soils, it is no longer recommended for highway plantings. Both Cortaderias were purposefully introduced. Both threaten native ecosystems.
	Tall Fescue, Lolium arundinaceum. This grass is native to Europe and North Africa. It is a cool season, perennial bunchgrass. Tall fescue invades native grasslands, savannas and woodlands. It was spread in misguided conservation plantings and pasture forage. Many ground-nesting birds like Bobwhite quail cannot use this grass for food and shelter. At this time this grass is scattered in States like, Arkansas, Georgia, Kansas, Idaho, Iowa, Louisiana, Missouri, Nebraska, New Jersey, Oklahoma, Oregon, Tennessee, Washington, and Wisconsin. It is found in grasslands and disturbed sites and is thought to be allelopathic as well as poisonous to cattle and other herbivores.

Bibliography:

These grasses were described with the help of the following references:

Randall, John M. and Janet Marinelli, Editors, 1996. Invasive Plants, Weeds of the Global Garden.

Brooklyn Botanic Garden, Inc., New York

Czarapata, Elizabeth J., 2005. Invasive Plants of the Upper Midwest. The University of Wisconsin Press, Madison.

Swearingen, Jil, Ongoing. Weeds Gone Wild. The Plant Conservation Alliance, Washington D.C.