By Mark Czarnota
University of Georgia
Pansies are easy to grow, they come in a myriad of color
combinations and they can take cool weather when few other plants
can. No wonder they’re one of the Southeast’s premier bedding
plants. But even pansies can be troubled by weeds.
The weeds in pansy plantings are usually annual plants such as
common chickweed and annual bluegrass. In small plantings, most
can easily be controlled with mulches and occasional hand weeding.
In larger plantings, though, people often turn to herbicides to
control their weed problems. The number of chemicals you can use
in pansies is limited.
A few pre-emergent products are out there: Dimension (dithiopyr),
Pendulum and Corral (pendimethalin), Pennant (metolachlor),
Snapshot (isoxaben and trifluralin), Surflan (oryzalin) and XL
(benefin and oryzalin).
That’s all
The list is short. But these products can provide excellent
control of many weeds coming from seed. They’re designed to
control germinating seeds. They need a rain or watering of about
an inch within a week of when you apply them.
Some of them come in both granular and sprayable forms. Granular
herbicides are more popular with homeowners. They don’t require
any mixing. And they’re more forgiving when you don’t apply them
just right.
None of these products, though, control all possible weeds. There
are no “silver bullets” when it comes to herbicides. Most of
these products or combinations of them will control 80 percent to
95 percent of the weeds from seed.
You will likely have some weeds you can’t control with
pre-emergent herbicides. But most of those can be easily removed
by hand.
‘Established’
All of these products are meant to be used on established
pansies. The plants have to be in the ground for some time, and
the soil has to be settled around the root ball. You can settle
the soil by firmly pressing it around the root ball as you plant
and then watering the plants in.
Labels often stress that word “established.” The key is to avoid
letting pre-emergent herbicides reach the roots of plants.
Once weed grasses have emerged in pansy beds, only one product is
labeled to control them: Vantage (sethoxydim).
Vantage is mixed with water and sprayed over the top of pansies
to control emerged and actively growing grasses. It won’t keep
seeds from germinating.
Don’t apply Vantage on hot, sunny days. It can cause minor damage
to pansy plants then.
But wait…
All of these herbicides were labeled for use on pansies when this
article was written. But labeling can change. Make sure you read
and understand the label before using any pesticide.
As herbicides go off patent, many third-party manufacturers may
market them under different trade names. Glyphosate, the active
ingredient in Roundup, for instance, is now available in more
than 50 formulations.
Before using any herbicide, always consider the health of the
plant. Make sure to consider the plants’ cultural requirements,
too. A quick canopy of pansy flowers and foliage will help
outcompete the weeds.
Plant pansies where they’ll get only 4 to 6 hours of direct
sunlight. Make sure the site drains well and the soil is amended
with some organic matter. Test the soil. Make sure the pansies
are getting adequate fertilization.
Most important, make sure the pansy bed is mulched after you
plant. Besides adding organic matter and maintaining soil
moisture and temperature, mulches help keep weeds from
germinating.
A good 2-inch layer of pine bark, pine straw, or shredded
hardwood bark should help make for healthy, happy pansies.
(Mark Czarnota is an ornamental weed control specialist with
the University of Georgia College of Agricultural and
Environmental Sciences.)
