Phragmites Control in Delaware: Practical Tips ... · TheDelawareDepartmentofNatural...

The Delaware Department of NaturalResources and Environmental

Controlʼs Division of Fish and Wildlife(DFW) has been involved in Phragmitescontrol since 1949. At that time, moretraditional methods, such as mowingand burning the plant, were implemented.However, moving machinery through awet, muddy environment was difficultand often resulted in unacceptabledamage to the marsh. Moreover, thePhragmites would re-sprout the followingspring or sooner, with no apparent semblance of control.

Hindsight has taught us that the key to controlling establishedstands of Phragmites involves the destruction of the rhizome (under-ground stem) and root system. The control methods practiced early onin Delaware had little effect on this part of the plant.

In 1976, the DFW began experimenting with glyphosate-based herbi-cides made by Monsanto. Glyphosate is the common name for N-(phos-phonomethyl) glycine. It inhibits an enzyme critical to the formation of spe-cific essential amino acids in plants. When properly applied to the leavesand stems of actively growing vegetation, the herbicide is absorbed intothe plantʼs food-transport tissues (phloem) and translocated throughoutthe plant. This “systemic” action allows glyphosate to reach undergroundrhizomes and roots and eventually inhibit aerial stem production.

The DFW used the Roundup® formulation of glyphosate initially onan experimental basis. Roundup® is used for agricultural, industrial,and home-site vegetation control, but is not labeled for use in wet-lands. The product Rodeo® was introduced in 1982 and can be appliedto emergent weeds in all fresh and brackish water bodies. Rodeo® isdifferent from Roundup® in that it does not contain a surfactant, andthere is a greater percentage of glyphosate in its makeup.

Since the patent on Rodeo® has expired, there are several aquaticherbicides on the market that have the same composition (53.8% gly-phosate, 46.2% other ingredients) and the same labeling. As of thiswriting, known products include Aqua Neat™, AquaPro™, Aqua Star™,Aquamaster™, Glypro®, and Eagre®. (Note: Use of brand, trade, orcompany names in this article is for information purposes and does notimply endorsement.)

How to Control Phragmites on Your PropertyNon-Chemical Methods. Phragmitesʼ rhizomes (underground stems)

must be affected to have any success in controlling the plant. For smallpatches, or for landowners who do not want to use pesticides, repeatedmowing or hand-cutting of the aerial stems will gradually deprive therhizomes of photosynthate (food) and stress the colony.

University of Delaware scientists have observed that Phragmites hasthe ability to send up shoots for a year and a half even while kept in thedark. Thus, the re-sprouting shoots will need to be cut multiple timesover probably at least two growing seasons. This is very labor-intensiveand may not be practical over large areas or where travel is difficult.

For larger sites with water-control structures, such as impoundmentsites, manipulating flooding and salinity may be helpful. UD scientistsfound that increasing either salinity or flooding (timing flooding so asto use the most saline water from the estuary) decreased plant height,biomass, stem density, and stored reserves in the rhizomes. If the plantstems were cut near the soil and then the stubble was flooded, all theplants died.

Chemical Methods. Landowners may find that careful use ofglyphosate herbicides may be the most practical, economical, and effec-tive control method for the situation. Keep in mind that glyphosate prod-ucts are broad spectrum, which means the herbicide has the potential toinjure or kill any green vegetation with which it comes in contact. Anyseeds lying in the soil will not be affected. Once glyphosate comes incontact with the soil or water column, it has no herbicidal activity.

Timing is crucial when using glyphosate herbicides as they need to beapplied when sugars are being actively translocated into the rhizomes.

University of Delaware scientists determined that late July to earlyAugust just after the plant flowers is the ideal time for herbicide applica-tion since the plantʼs underground reserves are at their lowest, andsugar flow is at a maximum. Our experience with both aerial and groundapplications has shown acceptable control levels (>80%) when sprayedfrom the flowering stage until late October. As long as the plant hassome green tissue, it seems to absorb the herbicide.

For ground applications, we generally use a 11⁄ 2% solution of aquaticglyphosate (2 ounces per gallon of spray solution) along with LI-700®Surfactant (Loveland Industries) at a rate of 1⁄ 2% per total spray volume(0.64 ounces per gallon of spray). Although any non-ionic surfactantlabeled for use with herbicides can be used, LI-700 is a lecithin-basedproduct that has very favorable environmental fate characteristics.

The requirement to wait untilPhragmites flowers to spray it presentschallenges since the plant usually hasattained its maximum height at this point,ranging from 8 to 14 feet. Any sprayer thatcan direct the spray stream into or over thecanopy is suitable. I have heard oflandowners standing on ladders to getabove the plant to spray. The DFW hasused backpack sprayers while standing onpickup trucks or tractors, tractor-mountedsprayers, and skid-mounted sprayers thatfit in the bed of a pickup. Some landownersuse sprayers that mount on ATVs.

Landowners may have to experimentwith different nozzles to find one that cansend a stream of spray as opposed to afine mist. At least one-third of the stem shouldbe covered on a spray-to-wet basis. If thespray is dripping off theplant, the solution isbeing wasted.

Landowners maywant to hire a privatecontractor for thespraying. The Dela-ware Department ofAgricultureʼs PesticideCompliance Section maintains a list of aquatic certified pesticide appli-cators. Contact the department at (302) 698-4570 for more information.

Due to the difficulty of ground applications in wetland areas, the vastmajority of Phragmites spraying by the DFW has been done using ahelicopter. When spraying from the air, four pints of aquatic glyphosateare applied per acre at a total spray volume of five gallons/acre.Again, LI-700 surfactant is used at a rate of 1⁄ 2% per total spray volume(3.2 ounces per acre).

Ideally, the dead Phragmites stems should be burned off during latewinter following herbicide applications on large acreages. Burningremoves the shading effect from the stems and reduces the heavy litterto encourage more desirable plants. Physical removal of the stems byhand-cutting or mowing may be practical in small patches.

Landowners need to realize they are managing Phragmites ratherthan eradicating it in most situations. Multiple herbicide applicationsover several years may be needed to obtain a desirable control level,followed by “touch-ups.” Phragmites that occurs in scattered patchesprovides some wildlife habitat and may provide some filtering benefits.Leaving Phragmites alone where it typically grows well, like the uppermarsh, and keeping it from spreading through the interior marsh maybe the best a landowner can hope for with this remarkable plant.

Cost-Share Program for Landowners. Since 1986, the DFW hasoffered a cost-sharing program for landowners who have five or moreacres of Phragmites to treat. The program is not intended for developedareas in part due to the difficulty in treating around houses by helicopter.Combining state and federal funds has reduced landowner cost toapproximately $4 to $5 per acre the last several years. Interestedlandowners can contact the DFW at (302) 739-9912.

(Continued from page 4)Phragmites makes an excellent model

for a successful weed. It has an extensivesystem of rhizomes that lives through thewinter, serving as a bud bank for newshoot growth in the spring.These rhizomes extend down to a depth

of more than 3 feet. From late summerthrough fall, Phragmites directs carbo-hydrates produced from photosynthesisdownward to its rhizomes, where the foodis stored for the plant’s spring growth andthe expansion of new rhizomes and stolons.At UD’s Halophyte Biotechnology

Center, marine botanist Jack Gallagherdetermined that by autumn, Phragmiteshas stored enough fuel in its rhizomes thatit can live in the dark, continually sendingup new shoots for one-and-one-half years.Thus, this plant can sustain severe dam-age to its aboveground shoots and stillhave enough fuel reserved to put up newshoots, which explains why mowing orburning alone cannot control this speciesin the long term.

Phragmites’ ability to tolerate high-salinity, coastal ocean water (containing3% salt) also contributes to the plant’scompetitiveness along the coast. Even at

such high-salt concentrations, thisresilient plant maintains the ability to fixcarbon from the atmosphere and transportand store the resulting carbohydrates in itsrhizomes below ground. Thus, while theplant’s growth may be reduced, it is notstopped. This ability to tolerate and thrivein saline conditions allows Phragmitesto compete with not only freshwater andbrackish tidal marsh plants along theborders of mid- to upper estuaries, butalso with true salt-marsh plants.

Able, K. W., S. M. Hagan, and S. A. Brown. 2003.Mechanisms of marsh habitat alteration due toPhragmites: Response of young-of-the-yearmummichog (Fundulus heteroclitus) to treatmentfor Phragmites removal. Estuaries 26: 484 – 494.

Armstrong, J., W. Armstrong, P. M. Beckett, J. E.Halder, S. Lythe, R. Holt, and A. Sinclair. 1996.Pathways of aeration and the mechanisms andbeneficial effects of humidity- and Venturi-inducedconvections in Phragmites australis (Cav.) Trin. ExSteud. Aquatic Botany 54: 177–197.

Bart, D., and J. M. Hartman. 2003. The role of largerhizome dispersal and low salinity windows inthe establishment of common reed, Phragmitesaustralis, in salt marshes: New links to humanactivities. Estuaries 26 (2B): 436 – 443.

Gratton C., and R. F. Denno. 2005. Restoration ofarthropod assemblages in a Spartina salt marshfollowing removal of the invasive plant Phragmitesaustralis. Restoration Ecology 13: 358 – 372.

Hansen, R. M. 1978. Shasta ground sloth food habits,Rampart Cave, Arizona. Paleobiology 4: 302 – 319.

Hellings, S. E., and J. L. Gallagher. 1992. The effectsof salinity and flooding on Phragmites australis.Journal of Applied Ecology 29: 41 – 49.

League, M. T., E. P. Colbert, D. M. Seliskar, andJ. L. Gallagher. 2006. Rhizome growth dynamicsof native and exotic haplotypes of Phragmitesaustralis (common reed). Estuaries and Coasts29: 269 – 276.

Molavi, A. 2003. Iraqʼs Eden: Reviving the legendarymarshes. National Geographic News.http://news.nationalgeographic.com/news/2003/05/0501_030501_arabmarshes.html.

Richardson, C. J., P. Reiss, N. A. Hussain, A. J.Alwash, and D. J. Pool. 2005. The restoration

potential of the Mesopotamian marshes of Iraq.Science 307: 1307 – 1311.

Rudrappa, T., J. Bonsall, J. L. Gallagher, D. M.Seliskar, and H.P. Bais. Root-secreted allelochemi-cal in the noxious weed Phragmites australisdeploys a reactive oxygen species responseand microtubule assembly disruption to executerhizotoxicity. Journal of Chemical Ecology.In press.

Saltonstall, K. 2002. Cryptic invasion by anon-native genotype of the common reed,Phragmites australis, into North America.Proceedings of the National Academy ofSciences (U.S.A.) 99: 2445 – 2449.

Seliskar, D. M., J. L. Gallagher, D. M. Burdick, and L.M. Mutz. 2002. The regulation of ecosystem func-tions by ecotypic variation in the dominant plant: ASpartina alterniflora salt marsh case study. Journalof Ecology. 90: 1 – 11.

Seliskar, D. M., K. E. Smart, B. T. Higashikubo, andJ. L. Gallagher. 2004. Seedling sulfide sensitivityamong plant species colonizing Phragmites-infested wetlands. Wetlands 24: 426 – 433.

USDA National Agricultural Library.http://www.invasivespeciesinfo.gov/plants/main.shtml

Wang, J. B., D. M. Seliskar, J. L. Gallagher, andM. T. League. 2006. Blocking Phragmites australisreinvasion of restored marshes using plantsselected from wild populations and tissue culture.Wetlands Ecology and Management 14: 539 – 547.

Warren, R. S., P. E. Fell, R. Rozsa, A. H. Brawley,A. C. Orsted, E. T. Olson, V. Swamy, and W. A.Niering. 2002. Salt marsh restoration in Connecti-cut: Twenty years of science and management.Restoration Ecology 10: 497-513.

Literature Cited

Phragmites Control in Delaware: Practical Tips & Techniques D E L A W A R E S E A G R A N T B U L L E T I N

by Denise M. Seliskar

Phragmites australis, or commonreed, is a tall, perennial grassthat is native to the United

States and grows on every continentexcept Antarctica. The plant has been inNorth America for at least 11,000 years. In1978, stem fragments of the plant, datingbetween 11,000 to 40,000 years old, werefound in the fossilized fecal remains of theextinct Shasta ground sloth in a cave in theGrand Canyon.In documenting the flora of the New

World, early European naturalists describedPhragmites as a minor wetland plant, usu-

ally confined to the upper elevations of the wetlands andalong the edges of ditches and ponds. In 1910, there wasone report of Phragmites being plentiful in swampsbehind New Jersey salt marshes, but as recently as 1950,Phragmites’ expansion was not considered a problem insaltwater environments in the United States.Over the past six decades, however, there has been a

rapid expansion of Phragmites into wetlands once dom-inated by other plants, including considerable spreadinto salt- and brackish-water tidal wetlands. In someareas, a monoculture of a salt-marsh plant with highecological value, such as smooth cordgrass (Spartinaalterniflora), is invaded. At other locations, a diversecommunity of brackish to freshwater plants is over-taken by Phragmites. Such a widespread invasion isdetrimental to wetland values because it disrupts thenatural hydrology (distribution and movement of water)and plant architecture of the marsh, thereby affectingthe marsh’s function.Today, Phragmites is considered an invasive species

because of its rapid expansion and the problems itcauses. The U.S. Department of Agriculture’s NaturalResources Conservation Service defines invasive plantsas “introduced species that can thrive in areas beyondtheir natural range of dispersal. These plants are charac-teristically adaptable, aggressive, have a high reproduc-tive capacity, and their vigor combined with a lack ofnatural enemies often leads to outbreak populations.”

Why Has Phragmites Become So Invasive?The reasons for Phragmites’ expansion in recent

decades are not well understood. In some cases, theplant’s invasion can be correlated with changes or dis-turbance in the environment, such as a drop in salinityand an increase in soil aeration where water flow in anestuary has been reduced, or where tidal flooding hasbeen restricted due to highway construction.Nutrient enrichment of rivers and estuaries may also

encourage the plant’s colonization. Due to its physiol-ogy, Phragmites can benefit more from higher nitrogenavailability than other common salt-marsh grasses, suchas Spartina and Distichlis. Yet many invasive situationsare unexplained by environmental factors, and there isaccumulating evidence that the expansion may be of anon-native genotype or strain of the species.

In 2002, Kristin Saltonstall, a scientist at Yale Uni-versity, analyzed numerous populations of Phragmitesincluding herbarium specimens from the early 20thcentury. Her research showed that a distinct strain —“Haplotype M” — appears to be the invasive form.It is thought to have been introduced to North Americafrom Europe.

This bulletin was published by the Delaware Sea Grant CollegeProgram and the Delaware Department of Natural Resourcesand Environmental Control (DNREC), with assistance from theUniversity of Delaware Office of Public Relations, ResearchCommunications Initiative. Tracey Bryant, editor; David Barczak,art director; and Pamela Donnelly, production coordinator.Delaware Sea Grant is a member of a national network of univer-sities committed to research, education, and technology transferdesigned to meet the changing needs of our ocean, coastal, andGreat Lakes regions. The program is funded by the NationalOceanic and Atmospheric Administration in the U.S. Dept. ofCommerce; the State of Delaware; and the University of Delaware.For more information, contact the UD Marine Public EducationOffice at (302) 831-8083 or MarineCom@udel.edu. For otherDelaware Sea Grant publications, visit www.ocean.udel.edu/seagrant.

Sea GrantDelaware

NATIO

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CEANIC AND ATMOSPHERIC ADMINISTRATIONU.S. DEPARTMENT OF COMMERCE

by Bill Jones,Phragmites Control Manager,

Delaware Dept. of Natural Resources& Environmental Control

Burning of Phragmites after herbicidal treatment.

Apply herbicidal controlsright after the plant flowers.

Bill Jones has been involved inPhragmites control efforts for thestate of Delaware since 1985.

This publication provides facts about Phragmites australis that support the funda-mental concepts and principles of the National Science Education Standards, as wellas the Delaware State Science Standards. It can be used to foster such activities asclassroom discussions about invasive species, student reports, laboratory and fieldinvestigations, and other educational projects.

For example, the techniques developed to control invasive Phragmites and to adaptthe plant for beneficial uses support several content standards including “Science andTechnology,” “Physical Science,” “Life Science,” and “Science in Personal and SocialPerspectives.” The discussion of Phragmites’ historical uses around the world and theplight of the Marsh Arabs support the “History and Nature of Science” standard.

For the Delaware State Science Standards, this publication contains conceptsand principles that meet the “Nature and Application of Science and Technology,”“Energy and Its Effects,” “Earth’s Dynamic Systems,” “Life Processes,” “Diversityand Continuity of Living Things,” and “Ecology” standards. Social Studies stan-dards, including Civics, Geography, and History, also are addressed and provide aninterdisciplinary approach to this extraordinary plant.

Meeting the Science Education Standards

9/07:10K

A stand of Phragmites, its fringed tassels aglow in the sun,borders a Delaware tidal creek.

Bob

Bowd

enDenise Seliskar (author of this publication)and Jack Gallagher, marine botanists andco-directors of the University of Delaware’sHalophyte Biotechnology Center, examinePhragmites in the greenhouse.

About the AuthorDenise M. Seliskar is a research scientistat the University of Delaware’s College ofMarine and Earth Studies, where she alsoco-directs UD’s Halophyte Biotechnology

Center. She has been studying the physiology and ecologyof wetland and sand dune plants for more than 30 years.

Phragmites’ rhizomes (underground stems) areeasily visible along this eroded creek bank.

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Phragmites australis:A Closer Look at a Marsh Invader

Can Mesopotamian Marshes Be Restored?

Beneficial Uses of Phragmites

Since Phragmites is widely distributed around the world, it is notsurprising that humans have found many uses for this tall, robust,

hollow-stemmed grass. A story is told in China of how Phragmitesrhizomes (underground stems) were harvested from the riverbanksaround a city and used as food, enabling the citizens to survive a win-ter siege in a war with a neighboring province. The young stems canbe eaten raw or cooked until tender. Older stems can be harvested,dried, and beaten to dislodge the largely carbohydrate “flour.” Stalksthat are wounded exude a gum that can be eaten raw or toastedwhen hardened. Gruel can be prepared from reed seeds.

The archaeological record substantiates the usefulness ofPhragmites to Native Americans for light arrow shafts to hunt birds and for tobacco holdersand woven mats. The hollow stems, or reeds, are used to make toys and jewelry. Theyalso are used to build boats in Peru and houses in Iraq (see below). In Great Britain, thereeds are of economic importance for thatching roofs. In eastern Europe, Phragmites isused as pulp in paper making.

A modern use, developed in Germany, for living Phragmites plants is in wastewatertreatment, where they speed up the drying of treated biosolids. Scientists at the Univer-sity of Delawareʼs Halophyte Biotechnology Center have developed a variegated (green-and-white striped) strain of Phragmites thathas great potential as a “sludge buster” fortwo reasons. First, since it does not produceviable seedlings, the plant cannot be spreadby the wind. Second, if plant stems orrhizome pieces should somehow escapefrom a wastewater treatment facility, thestrain could be easily recognized by its“stripes,” and the wastewater facility couldbe held accountable. Tissue-culture meth-ods for the mass propagation of this variantcurrently are under development.

Along the North and Mid-Atlantic coast of the United States, marshes dominated byinvasive Phragmites are considered to be ecologically unhealthy and less functional

than marshes occupied by the grass it replaced. But in the Middle East, particularly inIraq where the Tigris and Euphrates rivers meet, Phragmites marshes had been home toa people known as the Marsh Arabs for 5,000 years.

Their culture thrived in this region of Mesopotamia known as the “Garden of Eden,”where wetlands once covered some 7,000 square miles. They lived in houses made ofPhragmites in the lowlands along the marsh edges and on manmade islands built fromthe plant. They lived as a component of the marsh ecosystem — fishing, farming, raisingwater buffalo, and weaving.

Since the 1960s, more than 30 dams have been built on the two rivers, diverting waterfrom the wetlands. Then in the 1990s, the wetlands were dealt a lethal blow whenSaddam Hussein, angry at the Marsh Arabs for their uprising against him, diverted vastquantities of water from the rivers and conducted large marsh drainage projects. Thisresulted in the desertification of more than 90% of the wetlands in this once-rich andfertile region and displaced the Marsh Arabs from their homes.

Efforts to restore Iraqʼs Phragmites marshes are now under way. According to CurtisRichardson, a Duke University professor involved with the work, 20% of the originalmarsh area had been reflooded by 2004, and the Phragmites growing along the branch-es of the Tigris and Euphrates rivers which feed water into the marshes, is providingpropagules (seeds and/or pieces of shoots or rhizomes) to revegetate the reflooded

areas. Richardson believes thatalthough problems of high salinityexist and need to be addressed, thepotential for successfully restoringthis Mesopotamian region is high.

The variegated strain of Phragmites devel-oped at the University of Delaware (left) isplanted in the drying beds at the wastewatertreatment plant in Bridgeville, Delaware (right).

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The second and most common meansof Phragmites’ establishment in a tidalmarsh is by stolons or “runners” (stemsthat grow along the surface), or byrhizomes (stems that grow under-ground) from the upland fringe.

Phragmites typically grows along theupper edge of the marsh, and from here itcan send stolons of 30 feet or more overthe surface and into the interior of themarsh where the plant can root and putout shoots. By maintaining a connectionwith the mother plant in the higher eleva-tion, it is able to establish itself in theinterior of the marsh where soil condi-tions are not optimal. The mother plantcan provide the daughter plants with oxy-gen and nutrients until they develop largeenough structures to provide oxygen andfood to below-ground parts on their own.This process is called “clonal integra-tion.” In this way, the plant gets aroundthe problems faced by seedlings, such ashigh sulfide and low oxygen in the soil.

In our research here at UD, we foundthat “living fences” consisting of multi-layered walls of Baccharis halimifolia,Iva frutescens, Juncus roemerianus, andSpartina patens planted at key invasionpoints along the upper marsh edge wereeffective in restricting Phragmites’ spread.The third and probably least common

way that Phragmites establishes itselfin new territory is from vegetative frag-ments, such as pieces of stems, stolons,or rhizomes, that somehow break free andlodge in somewhat elevated hummocksor mounds in the marsh where the soilis better aerated. However, in order forthese fragments to successfully root,they need to be relatively large andburied in well-drained, low-salinity sites.Thus, construction, dredging, and otheractivities that disturb the soil may pro-vide an opportunity for Phragmites togain a foothold in new areas. Marsh Arabs collect Phragmites in a

mashuf (Arab canoe) in the remainingAl Hawizeh natural marsh on theIranian border in June 2003.

How Does Phragmites BecomeEstablished in a Marsh?

Phragmites becomes established in amarsh in one of three ways. First, seedscan germinate when they land in bare orsparsely vegetated areas with appropriatesoil conditions. In a mature marsh, vegeta-tive reproduction is the dominant means ofshoot production, and seedlings are seldomfound. However, in a restored marsh wherePhragmites has been cleared or in a newlycreated marsh where no vegetation ispresent, seedling colonization is a veryimportant means of plant establishment.One factor determining whether

Phragmites seedlings or those of desirableplant species will be the ones to colonizethe marsh is the amount of sulfide, asulfur compound, in the soil. The sulfidecontent depends on two factors. The firstis the amount of sulfate in the water thatfloods the marsh. Since seawater is anatural source of sulfate, the greater theproportion of seawater in the floodingwaters, the greater the amount of sulfate.Thus, marshes farther from the mouthof the estuary will contain less sulfateavailable to be converted to sulfide.The second factor is the oxygen level

in the soil. The less oxygen, the greateris the chemical reduction of sulfate tosulfide. Sulfide levels in soils of naturalSpartina alterniflora salt marshes alongthe Atlantic coast range from 0 to 7 mil-limolar (mM). Sulfide at even low levelsis toxic to most plants that have notevolved in soil containing this naturallyoccurring chemical compound. Andplants that are tolerant to high sulfidelevels when mature, such as Spartina andPhragmites, are not nearly so tolerantwhen they are seedlings.Our research at the University of

Delaware Halophyte BiotechnologyCenter determined the sensitivity ofseedlings of five marsh species thatmight be expected to colonize Mid-Atlantic bare salt- or brackish-marshsurfaces. Only Spartina alternifloraseedlings could withstand higher levelsof sulfide than Phragmites. Phragmitesseedlings tolerated up to 0.9 mM, butat levels of 0.9 to 1.6 mM, Spartinaalterniflora seedlings had the decidedadvantage. Therefore, Phragmitesseedlings would be able to colonize theless salty, brackish marshes; however,they probably could not live in the moresaline marshes at the mouth of the estu-ary due to the higher soil sulfide content.

The term “haplotype” refers to thegenetic makeup of DNA in the chloro-plast, the chlorophyll-containingorganelle in the plant cell. There arethree lineages of Phragmites australiscurrently recognized in North America:the native (Haplotypes A – H, S, Z,AA), the Gulf Coast (Haplotype I), andthe introduced (Haplotype M).

Regardless of the origin of the inva-sive form, substantial efforts have beenmade to control and reverse the spreadof Phragmites. Unfortunately, thesecontrol efforts often have been under-taken without knowledge of the poten-tial harm to native, non-invasivepopulations of the plant.

According to Robert Meadows,an environmental scientist at the Dela-ware Department of Natural Resourcesand Environmental Control, the non-invasive Phragmites may be less likelyto reestablish in an area where it wasinadvertently removed through herbici-dal spraying, leaving the area morelikely to be colonized by the invasiveform of the plant.Why Are We So Worriedabout Invasive Phragmites?

Salt marshes are nursery and feed-ing grounds for many species of fish,birds, and other animals we value.However, as noted earlier, when Phrag-mites invades a marsh, it changes theway the marsh functions by modifyingits hydrology and canopy architecture.For example, a natural salt marsh dom-inated by species such as smooth cord-grass (Spartina alterniflora), whichranges from 1 to 4 feet tall in Dela-ware, and other species, such asDistichlis spicata and Iva frutescensin the higher-elevation areas, can be

converted to a dense monoculture ofPhragmites (6 to 14 feet tall).

As Phragmites moves into a marsh,a dense rhizome (underground stem)network grows and a large volume ofplant litter accumulates, transforming asalt marsh once dissected with numer-ous tidal creeks carrying flood and ebbwaters into a much drier marsh withfew tidal creeks, no open pools, andless frequent tidal inundation.The filling of the tidal creeks

reduces access by fish to large areas ofthe marsh — areas important for feed-ing and reproduction. Even the arthro-pod communities in the marsh changesignificantly upon Phragmites’ inva-sion. For example, plant leafhopperand marsh spider populations decrease.

From the aboveground plant archi-tecture alone, one can see how themarsh’s usage by birds and otheranimals would be affected. The creek-bank habitat for large wading birds isdecreased, as is the resting and feedingarea for migratory waterfowl.Fortunately, however, the process

can be reversed. Marine scientistKenneth W. Able and his colleaguesat Rutgers University have shownthat fish usage is restored to a marshwhen Phragmites is removed andSpartina is allowed to re-vegetate themarsh surface. Natural arthropodcommunities return in time, as well.Likewise, usage of the salt marsh bybird species typical of that habitateventually is restored.

The vigorous wetland plant Phragmites australis,or “common reed,” has an interesting anatomy.

Take a look at the plantʼs majorparts, and then learn how someof these features give invasivePhragmites a competitive edge.Anther — the bi-lobed structure

that bears the pollen and sitsatop the slender filament; theanther and filament make upthe stamen (the male repro-ductive structure)

Culm — the grass stemFloret— small flower or repro-

ductive unit of a grass spikeletInflorescence — a cluster of

flowers having a common axisNode — region of a stem, rhi-

zome, or stolon from whichleaves, buds, or roots grow

Panicle — a branched grassinflorescence (flower cluster)with stalked spikelets

Peduncle — uppermost portionof the stem that holds theinflorescence (flower cluster)

Rachilla — central axis of aspikelet bearing the florets

Rhizome — horizontal under-ground stem that can produceroots and/or shoots at thenodes, thus allowing the plantto reproduce vegetatively

Spikelet — a flowering unit con-taining one or more florets

Stigma — that portion of a pistil (female reproductive struc-ture) that serves as a surface on which pollen germinates

Stolon — horizontal aboveground stem that can produceroots and/or shoots at the nodes, thus allowing the plantto reproduce vegetatively

What makes the exoticPhragmites more invasivethan the native form?University of Delawareresearch indicates the follow-ing: (1) the exotic emergessignificantly earlier in springthan the native, giving theexotic a longer growingseason; (2) the ratio of above-to below-ground biomass(weight) is much higher in thetaller exotic, indicating a moreefficient root/rhizome systemor higher-quality reserves;(3) the rhizomes of the exoticPhragmites have longerspaces between the nodes,which may enable fasterexpansion of the exotic population; (4) while native Phragmites hasmore buds per rhizome than the exotic form, the native buds remaindormant longer, resulting in the production of fewer shoots per rhizomewhen the canopy is damaged; (5) leaf pigment concentration is greaterin the exotic, allowing it to capture more of the sunʼs energy; and (6) theroots of the exotic exude more of a substance (gallic acid) that is toxicto other plants than do roots of the native Phragmites.

How do roots in saturated soils get enough oxygen? AlthoughPhragmites can tolerate a wide range of environments, the plant istypically found in wet, mucky areas. Phragmites can live in saturatedsoils thanks to a specialized network of air spaces and channels thatrun from the leaf sheaths to the stems, then down through the stemsinto the rhizomes, and out into the roots. One interesting means ofaeration in Phragmites, described by researchers Jean and WilliamArmstrong at the University of Hull, is “venturi-induced convection.”Gas flows via this mechanism when wind blows across the broken-offtops of tall, dead stems of Phragmites. This creates a vacuum, whichpulls gases through these taller stems from the rhizome systemconnected to shorter, less wind-exposed, dead, broken stems nearby.Thus, a gradient of flow from short, broken stems through the rhizomesystem to the tall, dead stems is operating and keeping the below-ground parts of the plant oxygenated even when the soils are hypoxic,that is, contain little oxygen.

These Phragmites plants were collectedfrom a low-salinity marsh along DelawareBay (left), and from a high-salinity site onIndian River Bay, Delaware (right).

Phragmites’ invasion causeschanges in the marsh-surfacetopography and elevation,making creeks and the marshsurface less accessible tofish. Restoration of themarsh can re-establish thisimportant function. Theblack area depicts the fillingof an intertidal creek dueto the accumulation of leafand stem litter and therhizome mat. The dotted lineindicates water level atmid-high tide. Figurereprinted with permissionof The Estuarine ResearchFederation and Dr. KenAble, Rutgers University.

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Phragmites: Lessons in Botany & Ecology

Native Phragmites (left) changes colorearlier in the fall than the exotic form (right).In summer, the native Phragmites has alighter, somewhat yellow-green leaf colorcompared to the grayer-green of the exotic.

Phragmites is usedto thatch houses inGreat Britain.

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Phragmites can extend stolons (runners) up to30 feet or more and then send up shoots whenit reaches advantageous soil conditions.

TaxonomyKingdom:Plantae (plants)Subkingdom:Tracheobionta(vascular plants)Superdivision:Spermatophyta(seed plants)Division/Phylum:Magnoliophyta(flowering plants)Class: Liliopsida(monocotyledons —one embryonic leafwithin the seed)Order: CyperalesFamily: Poaceae(grass family)Genus: Phragmites(reed)Species: Phragmitesaustralis (Cav.) Trin. exSteud. (common reed)� Native lineage� Gulf Coast lineage� Introduced lineage

Floret

Spikelet

Panicle

Floret

Peduncle

Rachilla

Anther

Stigma

Rhizomeor

Stolon

CulmNode

Spartina alternifloraReference

InitialInvasion

EarlyInvasion

Mid-Invasion

LateInvasion

Resto

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