Roadside Revegetation

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PLANNING PHASE TWO: ASSESS SITE
come from unwashed vehicles and hydromulch equipment and also from project
materials such as imported gravels, soil, compost, hay, and borrow material. After
construction, weeds can be brought from grazing animals.
The project team should consider developing a weed management strategy in the early
stages of planning that addresses how to control existing and potential weeds sources and
how to create a weed-resistant growing environment after construction. Ideally, this strategy
should be implemented two to three years prior to actual construction, continued through
the construction phase, and up to three years post-construction. Depending on the severity,
additional long-term treatments of weeds may be needed. The strategy must also address the
effects of each weed treatment on pollinator health and habitat, as well as water quality and
other project objectives. Inset 5-4 offers some guidance in developing a weed management
strategy.
The weed management strategy for a revegetation project should also conform to the IRVM
program that may have been developed for that particular highway. The IRVM is “an approach
to right-of-way maintenance that combines an array of management techniques with sound
ecological principles to establish and maintain safe, healthy and functional roadsides” (Brant
and others 2015). It applies many of the Integrated Pest Management concepts developed
for agriculture, horticulture, and forestry to roadside vegetation management. The IRVM
elements include prevention, monitoring, action thresholds, pest treatments, and evaluation
(NRVMA 1997). Most states use IRVM, and some have formal IRVM programs. Contact the state
Department of Transportation (DOT) for the individual IRVM program specific to the project.
5.8.1 WEED SOURCES AND THEIR GROWING ENVIRONMENT
The foundation of a weed management strategy is to create a growing environment that
encourages the development of a healthy native plant community that is resistant to the
introduction and spread of weeds. For most weeds to become established, there must first
be an opening, or space, in the native plant community for plants to grow. These conditions
occur in disturbed areas associated with recent construction or in places where native plants
and soil have been removed or disrupted. Secondly, the disturbed environment must be
favorable for weeds to take hold and thrive. This requires that the soils and climate be optimal
for the environmental needs of the species. Third, the weed species must have an advantage
over native species. If a weed is more resilient or robust in its growth habits in both adjacent
lands and disturbed sites, then it is more likely to become established.
While weed species come from sources already present on or adjacent to the project site,
they are also inadvertently brought onto the site from outside sources such as construction
equipment, cars and trucks, shoes and socks, and in materials used on the project such
as gravel and rock used for road construction materials. All too often, weeds arrive during
the revegetation efforts in contaminated mulches, topsoil, hydroseeding equipment, and
uncertified seed sources.
Inset 5-4 | General advice for
managing weeds (Sheley 2005)
The goal should be to develop
weed-resistant plant communities.
The first priority should be to
protect uninfested areas and
areas that have desirable species
available to colonize the
site once the weed species are
treated.
Establish not only early seral
species, but a diversity of midand
late-seral species filling
ecological niches in order to
prevent invasion of weeds.
Any prevention program should
be comprehensive and complete.
There are no silver bullets. Managing
weeds is time consuming,
complex, and an iterative process.
Try things and then adapt.
Early detection and rapid response
are critical to preventing
weed infestation. Develop a
systematic, thoughtful detection
strategy early in the planning
phases. Look for new patches or
problematic sources before they
spread, and treat appropriately.
Weed Sources – How to Assess
Weed populations are identified and located during vegetation surveys (Section 4.6.1, Vegetation
Assessment) and topsoil surveys (Section 5.11.1, Topsoil). County weed boards and county and
state road management staff are also a source of information, as they track and treat weeds.
From these surveys, a noxious weed map can be constructed that will aid in the development
of a weed control strategy for the project site.
The backbone of a weed control strategy is a thorough understanding of the life history and
ecology of the important weed species of the project. Information about many weed species
in the U.S. can be found on the PLANTS database (http://plants.usda.gov) in PDF documents
called Plant Guides located on each weed species Plant Profile page. The Invasive Species
Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat
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