Help Desk: Pre-emergent Herbicides for Weed; Safe to use in a home garden?

Dec 14, 2020

Weeds are a constant companion for the home gardener, and they can be a significant pest after a wet winter and if the temperatures are right. Where do these weeds mysteriously come from, one may ask?

Their seed has been dormant in the soil, waiting for the right conditions to come to life. However, weeds do not invade turfgrass appropriately fertilized, watered, and mowed at the correct height and frequency. Also, digging, tilling, and cultivating can effectively reduce or eliminate weeds in the garden and prevent adverse environmental conditions.


Therefore, most weed issues can be managed by using non-chemical methods like mulching, hand-weeding, and keeping the lawn healthy. Nevertheless, if the weed problem is substantial, the gardener may consider the use of a product called a Preemergent herbicide as a control method for these unwanted guests.

What are Preemergent herbicides?

Herbicides are chemicals that kill plants, and no one herbicide will kill every type of weed. Therefore, it is critical to match the product to the specific issue at hand and follow the instruction on the label. Preemergent herbicides work best when applied before the weeds' seeds germinate.

These chemicals also are designated as residual soil herbicides, and the control provided may last from many weeks to several years, depending on the particular compound, the rate used, and soil characteristics. They are used to control annual grasses and broadleaf weeds, and are applied to the soil, often as dry granules and sometimes as a liquid spray, then watered.

Certain preemergent herbicides require activation within 24 hours; others can wait up to 7 days and still others at 21 days. Again, consult the label for more information and instructions for safe application.

What risk should the gardener consider when using preemergent herbicides?

When applying anything in the garden, either organic or industrialized compounds, always keep safety in mind. The safe and legal use of herbicides requires following the printed information provided by the manufacturer or formulator of the chemical.

The label printed on the container tells how to use the product correctly and what special safety precautions must be taken to avoid harmful exposure. All products must bear the statement “Keep Out of Reach of Children” on the front of the label.

Near this statement, the gardener will usually find one of the signal words, CAUTION, WARNING, or DANGER. These words are a guide to the user to determine the level of toxicity or danger of the herbicidal product. CAUTION means short term toxicity. WARNING indicates that the herbicide is moderately toxic. DANGER specifies high toxicity, corrosiveness, and inducing irreversible damage to skin and eyes, and death if ingested. The use of protective equipment is highly advisable, particularly when mixing a product or making an application.

In summary

A better understanding of pests in the garden, together with frequent monitoring, allows gardeners to maximize their control efforts and minimize the use of a chemical in their backyard. Additionally, these practices will help reduce environmental contamination.

Consequently, an integrated pest management strategy is the best course of action to prevent the germination of weed seed as well as to protect animals and children.