Weed Management and Invasive Species Control - Project Planning and Management for Ecological Restoration - page 194

or after the seeded groundcover are controlled by mowing at the right time, with the right equip-
ment, and in the correct manner.
Theoretically, this is the most logical method of weed exclusion, because the first year of weed
control can be performed with a tractor-mounted mower, which can eliminate seed set of all Prior-
ity 2 weeds and many Priority 3 and 4 weeds as well. By mowing the site three to four times before
weeds set their seeds, the native forbs and perennial grasses, previously installed by seed, are en-
couraged to spread. It is important to use a rotary or sickle bar mower and adjust the height above
the grass culms (about five inches), so that the native grasses are not harmed during the mowings.
Also during this first year, Priority 1 species that reproduce vegetatively should be hand-pulled or
spot-sprayed as often as needed to eliminate them. This is important because the mowings will
encourage these weeds to spread if they are not otherwise controlled.
During year two, when the trees and shrubs are installed, and during year three, specific con-
trol of individual weeds can easily produce nearly complete control of Priority 2 weeds. Several
visits, however, may be needed each year due to the different times of germination, growth, flower-
ing, and seed set. During years two and three, the site should be surveyed for Priority 1 species, and
elimination performed if they exist. Thereafter, the trees, shrubs, and native groundcovers should
be established enough to not require further control of Priority 2 species. Priority 1 species should
still be surveyed for and eliminated if found.
Although this sequence of first planting and establishing a groundcover that can exclude weeds
makes sense, it is not always feasible because of budget and timing constraints. The following
situation is more typical.
GROUNDCOVERS SEEDED THE SAME YEAR OR ONE YEAR AFTER TREES AND SHRUBS ARE
INSTALLED
In this case, site preparation and preseeding weed control is even more critical than if groundcov-
ers are installed one year prior to trees and shrubs. Because the trees, shrubs, and any container-
ized groundcovers, and possibly the irrigation system, will create obstructions, tractor mowing will
likely not be possible unless wide spacing exists between plants. Some practitioners plant trees and
shrubs in widely spaced rows to allow for the use of tractors and mowers. If the plantings will be
irrigated, irrigation lines are installed along the rows of trees and shrubs to prevent interfering with
the use of equipment. The area between these rows is generally seeded with groundcover after the
woody plants and the irrigation system have been installed.
Specific control of both Priority 1 and 2 weeds should be implemented for three years, while
the trees, shrubs, and groundcovers are becoming established. If adequate site preparation was
performed and the seeding operation is successful, this task should not be excessive, although it
will likely be more labor intensive than if the groundcovers were installed one year in advance.
Both Priority 1 and 2 species should be individually controlled for three years, striving for com-
plete elimination, especially for Priority 1 weeds. Thereafter, the restoration plantings and main-
tenance regime should not be hampered by Priority 2 species, and active control of these species
can stop. Priority 1 species, however, should be surveyed for on an annual basis and eliminated if
found.