Tenacity Herbicide Review: A Cool Season Lawn Testimonial

One of the hottest products of 2019 has certainly been the rising popularity of Tenacity herbicide. Luckily I was able to get my hands on some from Do My Own for under $70 before they temporarily ran out of stock.

Made by Syngenta, Tenacity contains the active ingredient, mesotrione. This unique ingredient can not only be used as both a pre- and post-emergent herbicide, but can also be used to control more than 40 grassy and broadleaf weeds without affecting the germination of new grass seeds. 

After heavy core aeration and dethatching in the fall of 2018, and overseeding at 7 lbs./1,000 sq. ft. of Jonathan Green Black Beauty Ultra and GCI’s Premium TTTF, my grass came up nice and green. So green that I won the Jonathan Green ‘Show Us Your Lawn Content‘ for July 2019. However, there was one big problem: Creeping Bentgrass.

The core aeration propagated the bentgrass that was hiding under the soil. During the peak season, it was hard to notice – especially by those driving by or even walking along the sidewalk. However, the closer I looked, the more and more bentgrass I noticed. 

So, in late August, I started my attack. This was a little late in the game, particularly for Massachusetts cool season lawn, but we had a big lawn party on August 18th, and I knew I didn’t want to roll the dice with the possibility of a temporarily bleached lawn.  

Before the nitty gritty, here’s a quick overview of some frequently asked questions about Tenacity herbicide:

Tenacity Herbicide Application Rates

As a post emergent herbicide:

  • Use the syringe that comes with the bottle of Tenacity
  • Mix 1/2 teaspoon of Tenacity with 1 1/2 teaspoons of non-ionic surfactant to 1 gallon of water to cover 1,000 sq ft.
  • Spread evenly across lawn. Repeat in 10-14 days
  • Use a blue dye (optional) to avoid overlapping and ensure even coverage

As a pre-emergent herbicide:

  • Use the syringe that comes with the bottle of Tenacity
  • Mix 1/2 teaspoon of Tenacity to 1 gallon of water to cover 1,000 sq ft.
  • Water in with 1/4″ of water within 1-2 days of application

Be sure to always read the label before applying Tenacity herbicide.

How to Apply Tenacity Herbicide

  • Use the proper measurements as previously stated above
  • Fill a backpack sprayer with half of the total water (e.g. if you’re covering 2,000 sq. ft., then first fill to 1 gallon)
  • Add Tenacity herbicide and NIS (if using as a post-emergent) and fill with remaining water
  • Ensure product is mixed well – consider using a paint mixer drill attachment

Lawn Phix Tenacity Experiment

Not only was I up against an August 18th lawn party, but I also had to plan around the new roof being installed on the house on September 9, 2019. This 2-3 week period is the absolute sweet spot for overseeding for cool season lawns so the plan was made:

Tenacity herbicide post emergent applications:

  • August 19th and August 27th at full application rates. This is not ideal. If I had the time, these would have been spaced out two-weeks apart
  • September 12th dethatching, scalping, and overseeding
  • Starter fertilizer, Milorganite, and Kelp4Less
  • Daily waterings, 1-3 times per day

Midway through my Tenacity herbicide experiment, I was paranoid. “What did I do to my lawn?!“, I said everyday. I even had multiple neighbors come by and ask, ‘What in the world happened? Your lawn used to be so green‘. I had an ultra white, bleached lawn that I didn’t know if it was going to recover or not. “I’m never using this over-priced, over-hyped garbage ever again!“, I said on many occasions

Check out the images and timestamps below.

But low and behold, cooler heads prevailed and Tenacity didn’t disappoint. In fact, my lawn looks better than ever. There is only one small patch of bentgrass remaining that I will dig up and repair in the spring. 

The only word of caution: reset your expectations. I knew overuse of Tenacity herbicide could cause temporary bleaching of good turf grass, but I wasn’t expecting it. I used it on a friend’s lawn which I ‘consult’ for and did not have any bleaching of his good turf. While he had a bunch of crabgrass (which it smoked in two applications) his healthy grass stayed lush and green. 

I went from a non-believer to someone who will absolutely keep this gem in my arsenal. Whether I need to tackle bentgrass again, or simply want to add some to my tank to be used as a pre-emergent when overseeding, Tenacity will always be stocked on my lawncare shelf. 

Check out some more images below, along with the Tenacity herbicide video straight from Syngenta, and some links to buy these products on Do My Own

Have any questions or feedback? Do you want to share your experience with Tenacity? Please leave a comment below!




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