Tips
Weeds of the Month: Crabgrass and Carpetgrass
Did you know?
• Five species of crabgrass and three species of
carpetgrass are prevalent in Florida.
take the cold.
arrival of cooler weather, crabgrass and/or carpetgrass
are most likely the culprits.
and the lawn looks reasonably good from the sidewalk or
road. A weed, after all, is just a plant growing where it is
not wanted. But as winter stretches on, you may discover
that you suddenly have brown areas in your lawn that you
swear were green and healthy looking just a month or two
crabgrass and/or carpetgrass in your lawn. These are
grassy, warm-season weeds that die out in the cold but
come back with a vengeance in the spring. Carpetgrass
is a creeping, perennial grass with blunt, rounded leaf
a dense mat and will crowd out most other species.
Carpetgrass thrives in moist, sandy soils that are too wet
for bermudagrass and it tolerates more shade than does
bermudagrass. For these reasons, it is often planted in
low maintenance areas such as parks, roadsides, and
because of its frequent and prolonged production of
seedstalks. Crabgrasses are mat-forming summer annuals.
Depending on the species, the leaf blades may be one
to two inches long, and they produce slender, branched
seedstalks, similar to carpetgrass. Crabgrass is particularly
cold-sensitive, so as temperatures cool, patches of
crabgrass will be turning brown and dying out, but they
will almost certainly return in the spring. Unfortunately,
once crabgrass has germinated and begins to grow, there
are no herbicides available that can kill it without harming
your turf. The best way to manage crabgrass is to get
ahead of it with a pre-emergent
herbicide such as Dithiopyr and
Prodiamine. The downside is
that there is a narrow window of
herbicide application for best
results. Crabgrass germinates in
early spring when soil temperatures are 50 °F-55 °F or
greater. So, a pre-emergent herbicide must be applied
before soil temperatures remain above 50 °F for 24
far from perfect. Also, you cannot use a pre-emergent
herbicide on areas where you plan to put down new
sod. The only other option is to hand-pull the weeds
or spot treat with a nonselective herbicide such as
with sod. Maintaining healthy turf is the best way to
prevent crabgrass and carpetgrass from taking over
your lawn. Mow to the proper height (3.5 – 4 inches
for St. Augustinegrass) and mow often, so that you
turf minimizes the spaces where weeds can become
established and blocks sunlight that weed seeds need
Ralph Waldo Emerson described a weed as “a plant
whose virtue has not yet been discovered”.
For answers to your gardening questions, contact the
Hernando County Extension Service at 352-754-4433,
(extension.hernandocounty.us). Master Gardeners are
until noon, weather permitting.
Sources: Photos from University of FL
B y K a t h l e e n S h i e l d s ,
Silverthorn Resident and Florida Master Gardener
(With information provided by the University of
Silverthorn, Traditions Newsletter pg. 23
/(extension.hernandocounty.us