The main deciding factor for whether you use Quinclorac or Tenacity is the type of grass growing in your yard. While both products are designed to kill weeds and pest grasses without harming desirable grass, they are not compatible with all grass species. Quinclorac will kill St. Augustine grass along with weeds, while Tenacity is safe for St. Augustine grass. On the flipside, Tenacity is harmful to Bermuda grass, while Quinclorac can safely be applied to Bermuda lawns.
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Quinclorac vs. Tenacity: Head-to-Head Comparison
Both Quinclorac and Tenacity are broad-spectrum selective herbicides that attack broadleaf and grass weeds growing among turf grass. They are designed to be lawn-safe, but these products each have their pluses, minuses, and best applications.
For the purposes of this article, we will be comparing the following products:
- Quinclorac 75 DF: 75% Quinclorac concentrated product.
- Tenacity: Herbicide concentrate containing 40% Mesotrione.
An important thing to note is that both these products require mixing with water and a surfactant, such as methylated seed oil, for best results. Although Tenacity is currently only available in concentrate form, Quinclorac can be found combined with other herbicides in ready-to-use products, such as this weed killer spray.
What’s the Difference Between Quinclorac and Tenacity?
Both Quinclorac and Tenacity kill a similar spectrum of common weeds and pest grasses. However, the main difference is that neither herbicide is safe for all turf grasses. It’s important to choose the right weed killer spray for your lawn.
- Both Quinclorac and Tenacity attack a wide variety of broadleaf and grassy weed species, including crabgrass, foxtail, dandelion, and clover.
- Quinclorac is harmful to St. Augustine, Centipede grass, Bahiagrass, Dichondra, and several types of Bentgrass.
- Tenacity is harmful to Bermuda grass, Zoysia, Seashore Paspalum, and Bentgrass.
- Quinclorac is a post-emergent weed killer only.
- Tenacity works as a post-emergent weed killer and a pre-emergent that stops new weeds from sprouting.
- Quinclorac is better at killing mature weeds and crabgrass than Tenacity.
- Tenacity is best used on young weeds (under 30 days old) and as a pre-emergent control.
Quinclorac is more effective at killing mature crabgrass than Tenacity. However, Tenacity both kills existing weeds and prevents new weeds from sprouting. In comparison, Quinclorac only kills the weeds present in the yard—it doesn’t stop weed seeds from sprouting.
What is the Best Use for Quinclorac?
Quinclorac is a powerful post-emergent weed control with excellent results in killing crabgrass and clover, along with several other grassy and broadleaf weeds. It can be applied to young weeds or mature weeds of all sizes throughout spring and summer.
- Use Quinclorac as a crabgrass killer on Bermuda and Zoysia lawns, where Tenacity would be harmful to your turf grass.
- Quinclorac can be used to kill both young and mature weeds through spring and summer.
- Note: Quinclorac can be used in fall to kill some winter annuals, but is not effective at killing Annual Bluegrass (Poa Annua).
Remember, Quinclorac will only kill the weeds and pest grasses that are visible in your yard. To prevent new weed seeds from sprouting, you will have to apply an additional pre-emergent herbicide.
What is the Best Use for Tenacity?
Tenacity works as both a pre-emergent and post-emergent herbicide. Although Tenacity is not as effective at killing mature weeds as Quinclorac, it can kill weeds under 4 weeks old just as effectively as Quinclorac. Also, it remains in the soil for 30 days, acting as a pre-emergent to stop any new broadleaf and grassy weed seeds from sprouting.
- Use Tenacity in St. Augustine and Centipede grass lawns where Quinclorac will attack the grass.
- Apply Tenacity in spring to kill weeds as they sprout.
- An application of Tenacity will remain in the soil for up to 30 days, killing weed seeds as they sprout.
- Although not listed on the Tenacity product label, university studies have shown success using Tenacity to control and kill Annual Bluegrass (Poa Annua).
One of the biggest benefits of Tenacity is that it is very safe for use at the same time you are seeding or overseeding grass. Unlike most pre-emergents, it will not inhibit most turf grasses from sprouting.
Does Tenacity Herbicide Kill Crabgrass More Effectively than Quinclorac?
Tenacity and Quinclorac are both effective crabgrass killers. However, Quinclorac has a much higher success rate when applied to mature crabgrass at the three- and four-tiller stage than Tenacity. If you have a summer yard overrun by large crabgrass bunches, Quinclorac is the best option.
- Both Tenacity and Quinclorac are effective crabgrass killers.
- Quinclorac is more successful at killing mature crabgrass at the three-tiller and four-tiller sizes.
- Tenacity works as a crabgrass killer and preventer. If applied in early spring it will kill all crabgrass seedlings and prevent new crabgrass from sprouting.
Because Tenacity wipes out young crabgrass and prevents new crabgrass seeds from sprouting, it is the best option for an early spring application. By applying Tenacity to turfgrasses when soil temperatures rise past 55℉ (13℃), you can kill and prevent crabgrass for an entire season.
What’s Safer for Grass Seed: Quinclorac or Tenacity?
Tenacity is safer for grass seed than Quinclorac. As long as the seed mix contains less than 20% Fine Fescue by weight, Tenacity will not prevent germination or harm grass seedlings. This means you can overseed a Kentucky Bluegrass lawn and spray Tenacity at the same time. Your grass will sprout up, but weeds won’t.
- Tenacity is safer for grass seed than Quinclorac.
- Tenacity can be applied to lawns that have been seeded, or will be seeded, with seed mixes containing less than 20% Fine Fescue.
- Quinclorac may be safe for grass seed on a case-by-case basis.
Quinclorac can interact negatively with some grass seeds. Although it is perfectly safe for Tall Fescue, Annual Ryegrass, Buffalo grass, Bermuda grass, and Zoysia, it should not be applied to lawns where Kentucky Bluegrass, Perennial Ryegrass, or Fine Fescue has been seeded in the last 28 days.
Can You Mix Tenacity and Quinclorac
Currently, no commercial products mix Quinclorac with Mesotrione, the active ingredient in Tenacity. No studies are available on the reduced or increased effect of the mixture. Mixing herbicides is potentially dangerous and can lead to unintended side effects. When using any herbicide, follow the application instructions listed on the product label. You should never mix herbicides at home.
- Quinclorac and Tenacity are currently not combined in any commercial products.
- Mixing Quinclorac and Tenacity could be less effective than using 1 product on its own, or it may have negative side effects to your grass and soil.
- Home-mixing of chemical herbicides is not recommended.
Both Quinclorac and Tenacity are strong enough that either product applied correctly on its own should be enough to kill an exhaustive list of weeds. It isn’t worth the risk of damage to your lawn to try and combine these herbicides.
Which is Better: Quinclorac or Tenacity?
Quinclorac is better at killing established lawn weeds, especially established crabgrass, than Tenacity. It should be used in summer applications to kill mature weeds of all sizes. It should especially be used in Bermuda and Zoysia lawns, where Tenacity would kill the grass.
Tenacity works as both post-emergent and pre-emergent herbicide. It should be applied in early spring according to product label rates to kill young weeds and stop new weed seeds from sprouting for up to 30 days. Use Tenacity in St. Augustine and Centipede grass lawns where Quinclorac would attack the grass.