The Label is the Law: How to Choose a Herbicide

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May 15, 2017 at 9:45 am Category:

Learn to recognize the types of weeds and choose your herbicide accordingly

A lot of homeowners are satisfied with a decent yard if it isn’t the worst on the block.

Little do they know that upgrading your landscaping can increase the value of your home by 5 – 15%*. Chances are you’ve peered out your window to look at your neighbors’ lush, bright-green yard and asked, “What’s the best weed killer for lawns?” Relax, you’re in the right place. It’s safe to assume you’re researching pre-emergent and post-emergent herbicides because there’s an outbreak or annoyance of weeds in your lawn. Correctly identifying the target weed prior to purchasing or applying the herbicide is critical. You’re most likely dealing with:

  1. Annuals – Grow, produce seeds & die within a single year. Easiest to kill, generally.
  2. Biennials – Live for two years, first year is vegetative development followed by flowering and seed development.
  3. Perennials – Live from season to season producing seeds each year.

In addition to the three types of common lawn weeds listed above, they can be further distributed into two groups: broadleaf and grassy weeds. Broadleaf weeds typically have wider leaf blades and do not resemble grass (ex. Dandelion). Broadleaf weeds will often bear colorful flowers of different shapes and sizes. On the other hand, grassy weeds have long, narrow leaves void of any color or unique leaf shape. The ability to identify grassy weeds typically depends on recognizing growth habits, vegetative features and seed heads.  Start studying!

Completely preventing weeds can be a difficult challenge as weed seeds are spread in a variety of ways: wind, water, animals, soil amendments and even lawn equipment. Ensuring proper watering, fertilization, drainage and other techniques can help keep your lawn as healthy as possible.

Remember, don’t mow your grass too short as it will decrease the grass’ ability to shade the soil from sunlight, increasing the potential for weed germination.  On that same note, don’t mow immediately before or several days after application as more available leaf surface on the weed is better for absorption. Make sure to inspect your lawn frequently to look for new weeds that have germinated and require treatment.

We can divide herbicides into pre-emergent and post-emergent categories. A pre-emergent herbicide is applied prior to germination and before the weed has emerged. Oftentimes pre-emergent herbicides are used to control annual weeds. A post-emergent herbicide is used when weeds are already established (visible), or to spot-treat lone weeds.

When you take a closer look at the herbicides on the market, they can be further separated into two groups: selective and non-selective. Selective herbicides control the target weeds without damaging desirable turfgrass species. Non-selective herbicides kill all vegetation (including turfgrasses) and should be used on weeds not controlled by selective herbicides.


To understand some of the more complex nuances of the products and their chemistries, we connected with an expert, Jeff Schmidt, Midwest Sales Representative for PBI Gordon, and he was able to provide some applicable advice on using herbicides on your home lawns.

What factors specific to a home lawn would determine the right product or brand of pre- or post-emergent to use?

One of the main factors for post-emergent broadleaf weed control is air temperature. Using the correct formulation of post-emergent herbicide will aid in control of the target species.

  • Amine herbicides tend to be better suited for warm-weather. Some examples of Amines are Surge® and Q4® Plus.
  • Esters are generally more suited for cooler temperatures, and penetrate the leaf surface better than water-based chemistries. Examples of esters include SpeedZone® and PowerZone®.

How important is it to water in the herbicide vs. the drying period?

When applying post-emergent broadleaf herbicides, drying time is a critical factor. Active ingredients won’t work as well if they’re not allowed to be taken up by the targeted plant. And, if the product is still wet when it rains, the product may be washed off and not taken up by the plant.

The product label will often state the rainfast period. For example, Surge® Broadleaf Herbicide for turf is rainfast in as little as six hours, whereas TZone™ SE is rainfast in as little as three hours. Esters typically have a shorter rainfast period compared to amines, as esters move into the plant surface much faster than amines.

If using a granular weed-and-feed, application should be made when the dew is on the turf in the morning. The product should not be watered-in for 1-2 days. This allows the herbicide active ingredients to stick to the target weeds. Refer to the label when using granular weed-and-feed products.

Why might someone see different results when seemingly applying a herbicide in the same manner? (Ex. external factors that may affect chemicals effectiveness)

As mentioned above, temperature comes into play when selecting the right formulation of broadleaf herbicide (amine vs. ester). There are other factors that can also affect a successful application as it relates to environmental conditions, including wind, dry conditions, and excessive temperatures (hot and cold).

Another less-publicized factor is accurately calibrated spray equipment. It is critical to know the spray volume as it relates to square footage a sprayer is covering. This ensures the right amount of product is being applied to each site. Knowing the spray coverage per 1,000 sq. ft. is critically important for effective weed control, especially tough to control weeds such as white clover, ground ivy and others.

Why is timing so critical?

Application timing is vital in broadleaf weed control because knowing the target weed life cycle can result in a successful application.

Finally, deciding on the correct herbicide to treat your (or your client’s) lawn is not as simple as one would hope. With lots of different choices on the market and in the stores, pay close attention to the label, description and which weeds you need to control.

Some herbicides on the market will target both broadleaf and grassy weeds. For instance, PBI Gordon offers Q4® Plus  which is a post-emergent for both broadleaf and grassy weeds. A couple of other post-emergent options include Defendor from PROKoZ which specifically controls broadleaf weeds and Drive XLR8 from BASF which targets crabgrass.

You should be able to get a handful of meaningful information from the product label such as ingredients, restricted uses, specific uses, personal protective equipment, application directions and weeds controlled. If you ever have any questions or confusion regarding which herbicide to use and how to use it, please reach out to a local Reinders professional for help. When in doubt, remember: the label is the law.

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