September 2016

The "nom de plume" of plume grass is: EMERGING INVADER

Contact: John Peter Thompson | ipetrus1@msn.com OR
Kerrie Kyde | Kerrie.Kyde@Maryland.gov

Photo: The Nature Conservancy, Bugwood.org

Photo: Joseph DiTomaso, University of California Davis, Bugwood.org

ANNAPOLIS, MD (September 01, 2016) - Plume grass, or Ravennagrass (Tripidium ravennae ssp. ravennae, and many synonyms) is a botanical cousin to sugar cane. But its escape from ornamental plantings to naturalized patches is not so sweet. Reported as escaped in natural landscapes of the lower Chesapeake Bay and as highly invasive along the Colorado River in the Grand Canyon, plume grass is described by the National Park Service as "highly competitive" and as providing "little bird and wildlife cover." While not widely distributed in the mid-Atlantic, ravennagrass appears to be increasing in Pennsylvania, D.C. and Maryland. This tall grass sports huge plumes of pale purple-brown blooms in late summer, so it is most recognizable at this time of year. For this reason, the Maryland Invasive Species Council has named ravennagrass as the September Invader of the Month.

Plume grass is a tall clumping grass with a basal tuft of leaves and flowering stalks that reach heights of 8-12 ft., towering over big bluestem and other plants and making the plants easily visible from a distance. An individual plant can form a clump several feet in diameter. The gray-green leaf blades, which can be more than 3' long and up to 1" wide, have a bright white mid-vein on the undersides. Stem leaves occur the length of the culms up to the base of the inflorescence. The flower heads are as much as 2' long and feathery, turning a silvery color as summer turns into fall. Each panicle is composed of small branchlets, which in turn contain thousands of individual seeds in two-floret spikelets. Within a spikelet, one floret is sessile; the second has a short stalk. The seeds have short awns, bristles that extend beyond the length of the seeds, about 1/4" long. The seeds are primarily dispersed by wind, but can float and be distributed by water.

Plume grass is native to southern Europe, western Asia and North Africa; the grass was introduced to the U.S. for ornamental purposes, and is reported from the horticultural trade as early as 1921. Ravennagrass can grow in well-drained garden soils. It is relatively adaptable, can survive droughts, and can tolerate some shade. When it escapes, it is found along roadsides and disturbed areas and is especially successful in moist soils. Open, sunny riparian areas are susceptible habitats for this grass.

Photo: Joseph DiTomaso, University of California Davis, Bugwood.org.

Because this species is an emerging invader, relatively little is known about its ecological impacts. Both Washington and California have examined ravennagrass records - it is spreading in both states. The Washington Noxious Weed Control Board's concerns about this plant's impacts, derived from the experiences of land managers, include: its ability to form dense stands and reduce native plant diversity by competition and shading, and that it may promote fire similar to another tall grass invader, pampas grass. Some species of Saccharum (a commonly used synonym for this plant) can hybridize naturally with closely related genera, some of which also have invasive members, like Miscanthus, Imperata and Sorghum.

Plume grass is a clumping grass and not strongly rhizomatous the way common reed, or Phragmites is, but mechanical control requires removing ALL the roots to prevent resprouting. Removal should be done before the plants go to seed to prevent dispersal of the wind-borne seeds. Spot treatment with foliar applications of glyphosate have had some effect. No biological controls currently exist for this species.

For more information about other Invasive Species of Concern in Maryland, visit the Maryland Invasive Species Council or call the Maryland Department of Agriculture at 410-841-5920.