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Herbicide Knowledge Required to Control Weeds

One of the most laborsome chores for landowners and homeowners is controlling weeds and brush.  The constant mowing, trimming, pulling, and spraying of unwanted vegetation is a constant and aggravating battle during the peak spring and summer months.  The frustration only increases when the nuisance plants just re-grow, come right back, and all that work was for no avail.   When nothing else will grow, one can bet the weeds sure will.

Herbicides are usually the method of choice to provide longterm or permanent weed control. To add fuel to the fire of frustration is when herbicides don’t seem to work or provide long lasting control.  Herbicides can be expensive and time consuming to apply,  so they better work.  A better understating of how herbicides work and plants react might be in order.

Herbicide Facts

Here’s a reality check for landowners and homeowners using herbicides.  You are not going to see pesky plants melt and cry out before your eyes as if you poured water on the wicked witch from the Wizard of Oz.  One has to have realistic expectations. Herbicides today just don’t work that way.

Herbicides are effective because they hinder or stop processes in a plant that are essential for life.  This is referred to as the mode of action. They might regulate growth, effect photosynthesis, block enzymes, etc. The effect of the herbicide can be slow or fast, depending on the mode of action or plant species.

For example, glyphosate, commonly sold as Round-up, once applied to a plant, translocates through the leaves.  It then inhibits amino acids blocking a specific plant enzyme. This process can take a while to occur thus is why weeds may not show signs of yellowing or death for a week or so.

The very popular broadleaf herbicide 2-4-D kills plants by mimicking a plant hormone that is important for growth. It actually overloads the plant with hormones that causes the weed to grow itself to death.  This type of mode of action is rapid and thus has quick visible results as seen in the leaf curling, yellowing, and then death.

The timing of the herbicide application is also very critical and can vary with weed species.  This can ultimately be the difference between success or failure – joy or frustration.  As a general rule, annual weeds are best controlled with herbicides when they are small and actively growing. For biennial weeds, apply herbicides when they are in the rosette stage of growth.  Established perennials and woody brush are most vulnerable in the bud to bloom stage, which often occurs in the early fall when food reserves are moving into the roots.

Brush is defined as woody shrubs, vines or trees that are undesirable in a specific location.  If you haven’t had much success controlling certain brush thus far, then your window of opportunity could be this fall.  Some brush species are harder to control than others. Plant size often dictates which application technique is required to achieve adequate control.  One may need to consider both foliar and cut stump applications. With plants storing food reserves, this means the fall season is a great time to tackle and spray some of those hard to kill plants like kudzu, privet, poison ivy, or sweetgum.

Buyer Beware

Lastly, do your homework on what herbicides are labeled for use on specific plants and locations.  There are lots to choose from, both homeowner and commercial products, so knowing which to buy and use can be quite confusing.  You must read the label and know what the product contains.  Don’t go by brand names or trust fancy phrases and images as many products are honestly marketed for consumer confusion.  Look for the active ingredient on the label in small print and be educated on what that is and really does. Herbicides can also be very expensive as well as an costly mistake on your lawn or garden if you buy the wrong thing.

Success is knowing these facts and using it your benefit and to the demise of the weed.

by Shane Harris