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October 2017

Where Have all the "Flowers" Gone?
Invasive & Noxious Weeds along Maryland's Interstate Highways

For more information contact Shelley Brunelle: SBrunelle@sha.state.md.us

ANNAPOLIS, MD (October 01, 2017) - When did you last travel along congested I-495, I-95 between Washington DC and Baltimore, or on US 50 toward Annapolis, and notice something missing? Missing are certainly not angry red taillights or flashing blue lights or even cautious amber work lights. Missing is the abundant green, often lush, tropical-looking vegetation crawling over fences and enveloping trees and shrubs. Green overstory trees remain above the cleared leaf-littered ground. More brown is apparent, particularly the brown of dead vines hanging from trees and on noise walls. "What is going on?", "It looks so much better!" and conversely, "The plants are gone! Now I can see the highway!" and "Are they going to be replaced?" are a few of the public comments received by the Landscape Operations Division of the Office of Environmental Design, Maryland Department of Transportation State Highway Administration (MDOT SHA). What IS going on? Where have all the "flowers" gone? It turns out that not all those "flowers" are beneficial, so the Maryland Invasive Species Council has chosen this topic for the October Invader of the Month.

Iris pseudacorus seedpod Iris pseudacorus rhizome
Before — Exit Ramp from I-495 to MD185 (SHA Photo)
After — Exit Ramp from I-495 to MD185 (SHA Photo)

Environmental pressure caused by invasive and noxious plants outcompeting and overtaking the natural vegetation, highway safety concerns, and recent state and federal directives have all combined to significantly increase the need for control of invasive and noxious plant species along Maryland's interstates. As a general maintenance practice, MDOT SHA's maintenance teams follow Integrated Roadside Vegetation Management (IRVM) Guidelines that outline general multi-faceted management principles. Using IRVM principles results in increased safety for motorists by providing clear recovery zones for wayward or malfunctioning vehicles, retaining clear sight lines and sign visibility, and minimizing hazardous objects such as failing trees. Appropriate treatment also improves the environmental quality and aesthetic appearance of the roadside. Ecosystem preservation is further enhanced by using these principles to manage surface drainage and control invasive vegetative growth, which could become harmful to desirable vegetation, the surrounding environment, adjacent property, and the public.

Several years ago, MDOT SHA began planning to achieve its vegetation management goals by addressing the invasion of undesirable plant species, safety concerns, and state and federal directives. To date, the agency has designed eight interstate highway projects, each project divided into two Phases. Phase 1 includes controlling 49 plant species likely to cause economic or environmental harm to the existing ecosystem or to be harmful to humans. After the plants are mechanically removed or treated with herbicides, the rights-of-way are monitored for up to 18 months and retreated for any regrowth. After the initial removal and monitoring periods, Phase 2 begins. During Phase 2, contractors restore invaded habitats by replanting appropriate primarily native vegetation. This revegetation phase is followed by another two years of monitoring and treatment for any regrowth. Once Phases 1 and 2 are completed within six to seven years after commencing, then monitoring of the roadside vegetation will be managed under a separate maintenance contract using standard IRVM principles.

SHA Treatment Map
IRVM Interstate Projects Map. (SHA)

Since 2015, MDOT SHA has implemented seven of the eight IRVM interstate projects. Their locations are shown on the map above. The eighth project (PG Co. I-495) is being designed and has not yet been advertised for bidding. Of the seven ongoing projects, six have progressed into the monitoring period of Phase 1.

Much remains to accomplish, over time. Ongoing maintenance to control the persistent invasive species and encourage the success of new plantings will be necessary to prevent invasive plant infestation from occurring to this extent again in the future. Community coordination will be needed to reduce potential off-property sources of dispersal. Seeds and root fragments are also dispersed by birds, animals, wind, water and relocated soil. Although the "flowers are gone" for now, the treated landscape will never be "free" of invasive species. These invasive and noxious weeds can be managed more economically in the future by carefully managing the landscape with an integrated approach.

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.



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