Weed Management and Invasive Species Control - Project Planning and Management for Ecological Restoration - page 190

Developing a Priority Rating System for Weeds on Your Restoration Site
It is important to identify all of the weeds on your project site so that the most aggressive weeds
receive focused control. Weeds deemed nonthreatening or temporarily beneficial are left undis-
turbed or are controlled only after the high-priority weeds have been controlled. This is because
(a) a large number of nonnative weeds normally exist, (b) it is often impossible to control all of the
nonnative weeds in restoration areas, and (c) a wide variety of wildlife species can take advantage
of some attributes (e.g., seed production) of weeds.
The following priority rating scale was developed to assist restoration project site managers with
preparing a site-specific weed control strategy. After identifying the weeds on your project site and
on adjacent properties (the latter is especially important for weeds that spread by windborne seeds)
and researching their ecology, place each species in one of the following four categories.
PRIORITY 1: VERY HIGH PRIORITY
Priority 1 species are perennial weeds that are generally the most aggressive weeds on restoration
sites. With a few exceptions, they reproduce mainly vegetatively (underground rhizomes in most
cases) and secondarily by seed. Vegetative reproduction permits them to spread rapidly and ex-
clude other groundcovers. All Priority 1 species are seen as a threat to the integrity of restoration
areas and should therefore be eliminated from the entire project area.
PRIORITY 2: HIGH PRIORITY
Priority 2 species are mostly biennial. They are very aggressive and commonly will create solid
stands. Priority 2 weeds are large and often spiny, making them a threat to newly planted resto-
ration areas and making restoration site maintenance difficult. Priority 2 species should be con-
trolled for the first three years after installing groundcovers by seed in restoration areas, with an
attempt made to eliminate them from these areas.
PRIORITY 3: MEDIUM PRIORITY
Priority 3 species may be annual, biennial, or perennial. They are relatively low growing and
generally not disruptive to restoration plantings or to maintenance of restoration project sites. Nor-
mally, Priority 3 weeds need not be actively controlled. However, in certain areas where a specific
concern exists, control of Priority 3 species may be warranted.
PRIORITY 4: LOW PRIORITY
Priority 4 weeds may be annual, biennial, or perennial. They are low growing, are not disruptive
to restoration plantings, and do not interfere with restoration site maintenance. Priority 4 species
do not require active control.