Turfgrass competition. Maintaining a strong, vigorous
turf will help prevent the invasion of new weeds and help
to crowd out existing weeds.
To grow turf that will compete with weeds:
• Select the best turfgrass species for your area and use
recommended varieties.
• Maintain the soil pH between 6 and 7, if possible.
• Mow, water, and fertilizer properly.
• Control damage from insects and disease.
• Control thatch.
• Aerate compacted soil.
Mechanical control. Mechanical weed control includes
tillage before seeding the lawn, proper mowing, and hand
weeding. A few weeds can be pulled or dug by hand, but
hand pulling may not be effective on deep-rooted weeds.
Regular mowing at the proper height controls many kinds
of weeds.
Chemical control. For some weeds, herbicides may
be the only practical or effective method of control.
Herbicides are especially useful during new lawn
establishment or renovation of an old lawn. Once a dense
turf is established and maintained properly, weed problems
should be minimal. Do not depend on herbicides in lieu
of good turfgrass management. Chemical weed control
should be considered an aid to good management, not a
substitute for it.
Why Weeds Invade Lawns.
Improper mowing. Mowing too low and too
infrequently thins the turf, allowing weeds to get started.
Improper watering. Frequent watering encourages
weed seed germination, disease, thatch, and a shallowrooted turf that is less competitive with weeds for soil
moisture and nutrients.
Improper fertilizing. Fertilizing too much, too little, or
at the wrong time may benefit weeds more than grass.
Insect and disease injury. Weeds rapidly invade lawn
areas that are thinned by insects and diseases.
Compacted soil. Soil compaction is a hidden stress on
the turfgrass root system. The grass is unable to compete
effectively with weeds. Clay and silty soils are especially
prone to compaction.
Excessive wear. Turf areas that are used for recreation
and sports are subjected to wear and compaction. Weeds
become a problem in these areas, requiring intense weed
control and turf management.
Wrong kind of grass. The wrong kind of grass for the
location will gradually decline and be invaded by weeds.
Environmental stress. Weeds often take over a lawn
after it has been weakened and thinned from weatherrelated stresses.
Thatch.
Excessive thatch causes shallow-rooted grass
and contributes to insect and disease problems, which are
followed by weed invasion. Thatch also can reduce the
effectiveness of some soil-applied weed control chemicals.
