Herbicides work on different weeds

Graphic of herbicides.
Graphic of herbicides. Special to the Sun Herald

As you’ve been mowing your lawn, you’ve probably noticed a few things growing in you yard that aren’t what you want.

With warm weather comes a flush of growth that effects more than centipede or St. Augustine lawns.A weed is any plant growing where you don’t want it to grow. A tomato plant in a cotton field is a weed. They can be classified into either perennial or annual weeds. These two can be subdivided into three other categories: broadleaves, grasses and sedges.

Before you grab your herbicide and start committing herbicide, you need to know, at least in general terms, what it is that you want to kill. What will work on one group may not work on another.

Broadleaf weeds include chickweed, dollar weed, Florida betony, oxalis and spurge to name a few. These types of plants have leaves with netted veins and often have showy flowers. Grassy weeds have parallel veins and hollow, rounded stems with nodes (joints). Flowers lack petals and are often inconspicuous.

Sedges, at first glance, look like grasses. But, they have solid triangular stems with out nodes. Our most common problem sedges are purple and yellow nutsedge.

Once you’ve identified your weeds, you can go shopping for a herbicide. Herbicides are, themselves, divided into two groups: reemergent and post emergent. Preemergents are used to keep seeds from sprouting and don’t effect grown plants. Post emergents attack existing plants. A few herbicides, such as Atrazine, act in both modes.

For control of broadleaf weeds, the most common available for use in lawns contains 2, 4-D, dicamba and mecoprop. These three herbicides have been around since the fifties and sixties and can be found in varying percents of active ingredients depending on the producer.

Grassy weeds are more difficult to control because your lawn is composed of grass. Most of the weedy grasses are annuals and can be controlled with applications of reemergent herbicides in September of February.

Sedges are the most difficult to control. They are usually found in compacted soils. Correcting the soil conditions can reduce future infestations. Basagram or Image for Nutsedge (imazaquin) are the best choices. Basagram will only control yellow nutsedge. Image for Nutsedge will control purple and yellow nutsedges but it will slow down the growth of your lawn. It’s best to use it in the Spring.

Some weeds are tough to control. With them, a brows-spectrum herbicide such as glyphosate (Round-Up) cab be used. Just be aware that it will kill almost anything green it touches.

If you use it in your lawn as a spot treatment, use a shovel to cut the grass roots around the weed. As a systemic, it can be translocated beyond the treated area via the roots.

No matter what herbicide you select, water your lawn the day before. This will allow the active ingredients of the herbicide to be adsorbed more quickly.

Make certain that you read and follow the label. No matter how long you’ve been using a particular herbicide, the producer can change the formulation with out advertising it. But, they have to show proper use on the label.

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