Tuesday, March 10, 2015

Mystery of the Month: Catch-Me-if-You-Can Grass

Phragmites —Native or Not?

By Carole Gernes

What sly, new, invasive grass mimics its closest relative so well that it can slip under our radar until its take-over is well underway?

The chameleon is the non-native invasive common reed grass; Phragmites australis australis; a European subspecies of a common reed that has become invasive in the United States.

Historically, it has been traced to an East Coast shipping yard, where it was thought to have entered the U.S. as ballast. It is a perennial, up to 15 feet tall, with large golden or purplish flowering heads in the fall. 

These plants spread via a thick underground stem (rhizome) network, resulting in a dense monoculture that is difficult to walk through. As the infestation grows, it excludes and replaces beneficial native plants. This grass has overtaken large portions of Great Lakes shoreline.

Phragmites rhizome

Part of the problem with this plant is the difficulty in differentiating it from the native, North American, common reed, Phragmites australis americana. Clues to identification vary with the season. 
In late winter and early spring, check to see if the plants have leaves attached to the stems and large, intact, thick fluffy, golden brown, seed heads. If so, the grass is likely the invasive subspecies.
 Early spring invasive common reed (Phragmites australis ssp. australis)
Photo credit Ken Graeve; MNDOT

If flower heads are few, thin, ragged-looking and leaves have fallen off from winter weather, it is likely a native plant.

Early spring native common reed (Phragmites australis ssp. americanus)
Photo credit Ken Graeve; MNDOT
In summer, look at the color of the plants. The invasive plant has bluish tinged leaves. The native plant leaf is more yellow-green. On close inspection, the native plant will have green stems throughout, with areas on the stem (nodes) that area a reddish-maroon color. If you rub your fingers along the stem of the invasive plant, it will feel slightly rough and look dull. The native plant’s stem will feel smooth and look shiny.

 Invasive common reed                                                                     Native common reed
Photo credits Ken Graeve, MNDOT
Once plants begin to flower, you may notice differences in the size and color of the flowering heads. The invasive variety has larger, fuller looking tops, which may have a golden or purplish color. The native plants have smaller, thinner, golden-colored flowers.

Invasive Phragmites australis                                                           Native Phragmites americana
Photo credits Ken Graeve, MNDOT

Because this past winter saw less snow than usual, some stands of common reed have been difficult to identify. The most definitive characteristics require measuring flower parts and other small parts.

Phragmites species begin to bloom in late summer to fall. Isolated patches do not set seed; they spread by rhizome. Size of infestations increase quickly in areas where additional, genetically diverse, patches are introduced, starting seed production. Seeds are set very late - in late October to early November. Once viable seeds are set, they jump-start spread of the plant.

Great Lakes Phragmites Collaborative is a good resource for more information about invasive phragmites. Download a PDF version of the Phragmite Field Guide to help you distinguish between native and exotic forms of common reed.

How can you help?

If you find a suspected infestation, contact coordinator Carole Gernes at 651-792-7977 or carole.gernes@rwmwd.org.
Volunteer! Free trainings for the Invasive Plant Patrol citizen science program will be held in March and April.
  • Saturday, March 28 - Shoreview Community Center  To register, contact Carole Gernes at 651-792-7977 or carole.gernes@rwmwd.org.
  • Saturday, April 11 - Maplewood Nature Center  To register, call 651-249-2170 or online at www.maplewoodnature.com.
  • Saturday, April 25 - Tamarack Nature Center  To register, call Melanie Harding at 651-407-5350 extension 119. 
Note:  All class times are 10 am – 2 pm, with a 30-minute lunch break. 

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