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CRABGRASS
Crabgrass is an annual weed that invades home lawns and gardens. It germinates when soil temperatures reach about 15°C
and air temperatures stay above 18°C
for at least five consecutive days. Crabgrass
usually establishes itself in mid to late spring.
There are two types of crabgrass that grow in Ontario, namely, large and
smooth crabgrass. Both types are
yellow-green in colour and have wide leaf blades that taper to a point at the
end. Crabgrass plants produce
finger-like purple seed heads when mature.
Seeds are produced over winter in the soil and germinate the following
spring.
Crabgrass normally invades lawns that are thin, weak and undernourished.
Crabgrass is rarely present in lawns that are properly fertilized,
watered and mowed correctly at a height of at least 5-6cm (2-2.5 inches).
The very hot dry summers that we experienced in 1998 and 1999 provided ideal
conditions for crabgrass to flourish on home lawns. Many homeowners did not
recognize that they had a problem with crabgrass until mid to late summer.
By that time, it was too late to apply a preventative or early
post-emergent crabgrass control treatment.
By late August and into September, crabgrass plants that were not
controlled produced large quantities of seed.
This year is
expected to be another bad year for crabgrass as a result of the abundance of
seed that was produced last fall. The
best defense against crabgrass is to promote a healthy, thick lawn and to have a
preventative crabgrass control material applied to your lawn this spring.
SPRING LAWN CARE
 
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CRABGRASS Crabgrass
is an annual weed that spouts from seed in late May to early June.
During the summer it develops into a ground-hugging weed that spreads
over surrounding grass. In late summer it produces hundreds of seeds
that will sprout the following year. Crabgrass seeds can remain in the
soil for many years and sprout when the soil is disturbed. |
Early spring lawns can appear straw-coloured and dead.
If the grass seems very dense and matted, you can help by giving the lawn
a good, vigorous raking. Remove the
piles of material and add them to your compost pile.
This raking opens up the turf to allow light, water and fertilizer
penetration. It stimulates the
grass plant and makes the lawn look much better.
If your lawn is very sparse and you have had a serious problem with
crabgrass in previous years, you may wish to apply a crabgrass control.
Crabgrass control is best performed in the spring in an effort to stop
crabgrass plants from germinating and growing.
After a crabgrass control has been applied, the soil surface should not
be disturbed. Raking or digging may
reduce the effectiveness of the crabgrass control material.
IS
IT CRABGRASS?
It
is not uncommon for our customers to call us in the early spring to help them
get rid of that *!#@* Crabgrass in their lawn.
If the weed grass is present in early spring, the problem is likely not
Crabgrass but instead a perennial weed grass such as Quackgrass.
Quackgrass is
extremely vigorous, and is taller, faster growing and lighter green than
desirable lawn grasses. Quackgrass
has a broad grass blade and a tough, wiry network of underground stems.
It is useless to treat Quackgrass with a “Crabgrass control product”.
Crabgrass control materials are only effective against crabgrass and
other annual grass type weeds.
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QUACKGRASS
is a perennial weed that resembles crabgrass but sprouts from roots.
Quackgrass often invades lawns from nearby fields. It is an invasive
weed that is almost impossible to pull by hand because it spreads by an
extensive underground root system. Typically, quackgrass will grow
faster than the surrounding lawn, so it is easy to recognize by its
taller height. Left on its own, quackgrass will quickly overtake an
entire lawn. |
There
is no selective weed control material for Quackgrass. The recommended procedure for control and/or suppression of
Quackgrass is to “stunt it out” or “crowd it out”. This is accomplished by supplying a good program of fertility
to the turf, in order to thicken it up. In
addition, the lawn should be mowed frequently (every 3 to 4 days) in the spring
and fall at a slightly reduced height than normally recommended, 5 cm (2
inches). This will help to stunt
the growth of the Quackgrass and encourage desirable grasses to crowd out the
Quackgrass.
CRABGRASS- CAN IT BE CONTROLLED?
Yes, but it’s not easy!
Control of Crabgrass is best done in spring, prior to or soon after the
germination and establishment of crabgrass plants.
Crabgrass seeds start to germinate when the soil reaches about 18°C
(65°F). This
is roughly the time when forsythias and lilacs bloom.
The most effective way to control Crabgrass is to apply a pre-emergent control,
such as Dimension®, just before the seeds begin to germinate.
This material will stop crabgrass plants from growing.
If Crabgrass still becomes established, a post-emergent treatment of Acclaim® may
be applied to completely rid your lawn of Crabgrass.
It is also very important that the desirable lawn surfaces be properly nourished
with fertilizer. A thick lawn will
shade the soil surface to help prevent additional Crabgrass seeds from
germinating during the season as the Crabgrass control barrier weakens.
Editor's Note:
Weedman CANADA will be
providing timely lawn care tips all season long. More information available at www.weed-man.com.
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