These articles are written to apply to the northeastern
corner of Illinois. Problems and timing may not apply outside of this
Plenty of Time for Managing
Crabgrass in Lawns
April 2, 1998
Warm weather and rain have greened up most lawns in recent days. Crabgrass
becomes a concern of many people as conditions warm in the Spring. There
are a variety of ways to manage crabgrass in lawns, and there is still
plenty of time to consider your options.
Crabgrass has an annual life cycle, which means any crabgrass present
in lawns in 1997 is dead, and the only way for crabgrass to appear in
1998 is by seeds germinating into new plants. Crabgrass seed will start
to germinate when soil temperatures get close to 60 degrees F and stay
there for several consecutive days. Crabgrass likes full sun, thinner
lawns, and frequent watering.
Keeping those preferences in mind, adjustments in lawn care practices
can have a major impact on reducing the chances of crabgrass appearing
in your lawn. Mowing height is a major one. Mow between 2-1/2 and 3 inches
and there will be fewer crabgrass plants in your lawn. Light, frequent
watering of lawns also favors crabgrass, so follow the general rule of
deep, infrequent watering for your lawn. Crabgrass often invades areas
seeded in late spring because of bare soil, frequent watering, and onset
of hot weather which is ideal for growth.
Preemergence herbicides (weed killers) can also be used in spring for
crabgrass control. These need to be applied to the lawn before crabgrass
germinates. Late April into early May is the suggested time for applying
preemergence crabgrass herbicide in northern Illinois. If April is unusually
warm , apply by late April; otherwise early May is not too late.
Most preemergence crabgrass herbicides are found as a combination with
lawn fertilizer at garden supply stores, so the crabgrass prevention and
spring fertilization can be done at the same time. Follow the rates given
on the bag.
One of the management problems associated with preemergence herbicides
is seeding or overseeding practices. With the exception of a herbicide
called siduron, all preemergence annual grass weed killers will also damage
germinating desirable grass seed. Siduron may be found as lawn starter
fertilizer with crabgrass preventer.