Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00001564
11/12/99
Lawn Weed Control
Weeds inevitably become a problem, especially on low
quality lawns. Controlling weeds involves more than
spraying a weed killer or herbicide. There are several
types of weeds and several types of herbicides.
Weeds can be either broad-leaved or grasses. Within each
of these two types, weeds may be annual or perennial.
Herbicide are post-emergent, pre-emergent or total
vegetation killer. The post-emergent herbicides kill
growing weeds and the most common example is 2,4-D.
Pre-emergent herbicides like Dacthal kill germinating
seeds so the plant never emerges from the ground. Total
vegetation killers kill any type of vegetation they land
on.
Perennial broad-leaved weeds are controlled with
post-emergent herbicides. When the weeds are young and
actively growing they absorb the herbicide readily, giving
good control. Post-emergent herbicides also control
annual broad-leaved weeds that were not controlled with
pre-emergent herbicides.
Pre-emergent herbicides kill annual broad-leaved weeds and
annual grasses, if they are applied before the seedlings
get established. Such herbicides must be applied before
seeds germinate.
Perennial grasses are controlled with total vegetation
killers. This type of herbicide is also used to
chemically edge lawns and to kill weeds in drives and
walks. Clumps of perennial grasses in lawns can be killed
with these chemicals but surrounding lawn grasses will be
killed as well. These chemicals vary in their toxicity so
read the label thoroughly before the chemical is
purchased. Total vegetation killers are often used prior
to lawn establishment.
Most lawn weedkillers contain 2,4-D so do a good job on
easily killed weeds such as dandelion, buckhorn and
plantain. When the lawn is infested with more
difficult-to-control weeds such as chickweed, ground ivy
or creeping charlie, use a product that contains 2,4-D
plus either Dicamba or MCPP. Some weedkillers contain all
three chemicals but will only control actively growing
broad-leaved weeds. Combination fertilizer\herbicide
products will control the easily controlled weeds but a
liquid will give better results when difficult-to-control
weeds are present.
The most common use of pre-emergent weedkillers is for
crabgrass control. These must be applied in April or
early May before the blossoms fall off the forsythia
bushes. These weedkillers are sometimes combined with
fertilizers for convenient application.
Total vegetation killers are available in squirt bottles
for spot treatment or they can be applied to larger areas.
Use one sprayer for herbicides and another for other
pesticides. A herbicide residue may linger in the sprayer
and injure plants during a subsequent spraying if only one
sprayer is used.
Do not spray on windy days. The small droplets will be
blown onto desirable plants and may cause injury. Use a
low sprayer pressure to increase droplet size and reduce
the possibility of drifting.
Do not use the sprayed clippings as a mulch for at least 4
weeks after applying a herbicide.
This information is for educational purposes only. References
to commercial products or trade names does not imply
endorsement by MSU Extension or bias against those not
mentioned. This information becomes public property upon
publication and may be printed verbatim with credit to MSU
Extension. Reprinting cannot be used to endorse or advertise
a commercial product or company.
This file was generated from data base ZZ on 01/19/00.
Data base ZZ was last revised on 11/12/99.
For more information about this data base or its contents please contact
heatley@msue.msu.edu . Please read our
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