Weed Management and Invasive Species Control - Project Planning and Management for Ecological Restoration - page 193

The area in the interior has little effect on the outward expansion of the colony but does con-
tribute to the weed presence by seed dispersal. This is reason enough to attempt to reduce the main
core population, in addition to the colonies, because this is the source of your satellite colonies.
If you have equipment at your disposal, such as bulldozers or tractors, then addressing these
satellite colonies may not be an issue. Equipment can eliminate the small colonies very quickly,
allowing concentration on the core area. Regardless of the equipment, however, it is important to
focus on the satellite colonies first and then proceed to the main weed population.
Timing of Weed Control
Timing of weed removal can greatly enhance the overall impact your efforts will have on the weed
population. As stated previously, whenever possible, invasive plants should be removed before they
have a chance to set seed. Waiting until after seed has set will require aggressive soil treatment or
manipulation.
A weedy tree species in the arid West of North America—the salt cedar originating from the
Mediterranean—has seed that is viable for only one season. By eliminating new seedlings and
eliminating the mature seed-producing plants, the salt cedar can be eradicated from a watershed
essentially in one season, because there is no seed bank for the species. Numerous volunteers and
volunteer groups have donated time and equipment to eradicate this plant from desert streams,
knowing that timing is critical to the goal of salt cedar eradication. In many cases, following salt
cedar removal, a dormant native seed bank has been able to germinate and reestablish a diverse
riparian habitat. The key to these efforts has been understanding how the species exists in the
landscape and using this knowledge as an advantage for the ultimate goal.
Weed Control Strategies at Ecological Restoration Sites
Ecological restoration areas generally require a more intensive weed control program than natural
areas. Because of the predominance of weeds in most project areas, it is not expected that resto-
ration areas will have 100 percent native groundcovers, even if native groundcovers are seeded.
As described earlier, Priority 3 and 4 weeds may be left uncontrolled, at least in the short term,
because they do not pose serious threats to restoration plantings or maintenance procedures, nor
do they justify the cost of control efforts.
Weed control programs at ecological restoration project sites should call for complete elimina-
tion of Priority 1 species and control of Priority 2 species, generally requiring intensive aftercare for
a three-year period. Control for Priority 2 weeds should be performed whether groundcovers were
seeded one year in advance of tree and shrub installation, were seeded at the same time as tree and
shrub installation, or were not installed at all. The approach, however, should be slightly different
in each case, as explained below.
GROUNDCOVERS SEEDED ONE YEAR IN ADVANCE OF TREE OR SHRUB INSTALLATION
In this approach to restoration, the preferred groundcover species are seeded at least one year prior
to the installation of trees and shrubs. During this first year, weeds that come up at the same time