Broadleaf Weed Problems in Lawns
Identifying the weed and trying to determine why it has invaded
is the first step in managing broadleaf weeds in lawns. Weeds can
be indicators of underlying problems. For example, ground ivy invades
lawns in shade, while knotweed may indicate soil compaction. Assorted
weeds may indicate overall poor conditions for lawn grasses and/or
After identifying the weeds present, step two for controlling broadleaf
weeds should be to review lawn care practices and make adjustments
as needed to assure a good stand of grass. Sound lawn care practices
should promote a healthy, vigorous turf able to prevent and compete
with weed invasions. These practices include proper selection and
establishment, fertilization, watering, mowing, thatch management,
and related practices. Alter the environment that may be favoring
weeds, such as reducing shade or improving poor soil conditions.
The third step is removal of existing broadleaf weeds. Pulling
by hand is one option; be sure to get as much of the root system
as possible. There are a number of broadleaf weed herbicides (weed
killers) available for use on lawns. Only apply to actively growing
weeds. Choices found in garden centers typically include 2,4-D (2,4-dichlorophenoxyacetic
acid); mecoprop or MCPP (2-(2-methyl-4-chlorophenoxy) propionic
acid); or dicamba (3,6-dichloro-o-anisic acid); with two and three-way
combinations available. Additional herbicides are available for
commercial landscape care services for use on lawns. The Illinois
Commercial Landscape and Turfgrass Pest Management Handbook and
Illinois Homeowners Guide to Pest Management offer the latest information
on various weeds and herbicides to control them.
Thoroughly read, understand, and follow all information on herbicide
labels. There are general guidelines for using broadleaf herbicides
on lawns. Avoid windy days, as these materials can damage many landscape
and garden plants if they drift (spray droplets land off the lawn).
Also avoid hot days (over 85 degrees F). It's best to have adequate
soil moisture, but no rain for 24 hours after application. Don't
mow for a few days before and after application. Consider spot treating
weeds rather than broadcasting weed killer over the entire area.
Use caution on newly seeded areas; wait 4 mowings before treating
a newly seeded lawn and wait 30 days before seeding an area treated
with broadleaf herbicides. Refer to the label regarding any potential
hazards when used on lawns over the root zone of trees (such as
Early to mid fall can be a good time to control perennial broadleaf
weeds, such as dandelions. Control may be good as weeds prepare
for winter dormancy and lawns fill-in bare areas created by the
weed dying readily in the cooler weather of fall. Spring and early
summer applications may not provide as good of control as fall.
In addition, warmer temperatures increase the chance of lawn injury.
Regardless the time of the year, weeds need to be actively growing
for herbicides to work.