Tenacity Herbicide (Mesotrione) Application Guide for Cool-Season Lawns

How Much Tenacity Per Gallon of Water?

Mix Tenacity at 0.5 teaspoon (about 2.5 milliliters) per gallon of water and spray that gallon over 1,000 square feet. The label's spot-application table lists 1 teaspoon of Tenacity and 3 teaspoons of non-ionic surfactant in a 2-gallon mix, applied at 1 gallon per 1,000 square feet, and Syngenta's own FAQ gives the same numbers for hand-held and backpack sprayers. So the per-gallon working mix is 0.5 teaspoon Tenacity plus 1.5 teaspoons surfactant per gallon. Use a flat-fan nozzle, wet the weed leaves without running them to drip, and give it at least an hour before rain or sprinklers. Tenacity works post-emergent on young, actively growing weeds and has some pre-emergent activity too, and the spot mix is the same either way.

Tenacity mixing chart by sprayer size

What size sprayer are you filling? Find the row, measure the Tenacity first, then the surfactant, then top off with water. The 2-gallon row is the label's own spot table. The other rows scale it at the same 1 gallon per 1,000 square feet.

How far does one bottle go? One fluid ounce is 6 teaspoons, so an 8-ounce bottle holds 48 teaspoons. At the spot rate, that is 96 one-gallon batches, enough to cover 96,000 square feet of spot spraying. A 1-pint (16-ounce) bottle of surfactant holds 96 teaspoons, which makes 64 gallons of mix at 1.5 teaspoons per gallon.

What Is Tenacity Herbicide? (Mesotrione Explained)

Before going deeper on rates, it helps to know exactly what you are spraying. Tenacity herbicide is a selective pre- and post-emergent weed killer for cool-season lawns, and everything it does traces back to one active ingredient: mesotrione. Mesotrione is the molecule doing the work, and Tenacity is the brand name on the bottle. Syngenta says it controls more than 46 broadleaf weed and grass species, before they sprout and after they are up, without harming the labeled turf types covered below.

Tenacity is Syngenta's brand name for a 4SC formulation of mesotrione, a selective herbicide originally derived from a compound that the bottlebrush plant uses to suppress competing vegetation around it. The label lists mesotrione at 40.0 percent and states the product contains 4 pounds of active ingredient per gallon, which is what "4SC" (a 4-pound suspension concentrate) means. Generic mesotrione products you will find online (Liquid Harvest, Atticus Torocity, several others) are sold as the same 4SC concentration, and at the same concentration the same label rates apply.

The mode of action is what makes Tenacity special. It is an HPPD inhibitor (Group 27 on the label), which is a fancy way of saying it blocks an enzyme weeds need to produce carotenoids. Carotenoids are the protective pigments that shield chlorophyll from sunlight damage. Strip those out and the plant's chlorophyll breaks down in the sun. That is why treated weeds turn ghostly white before they die. The bleaching is the kill signal, not a side effect.

For homeowner use, three things flow from that mode of action and matter every time you apply it:

• The white-out is normal. The label says treated weeds stop growing, turn white, and may take up to three weeks to die. Your turf can whiten a little too: the label says those symptoms show up 5 to 7 days after application and last for several weeks. If weeds do not whiten at all, look at the usual causes: no surfactant, mature or drought-stressed weeds, or a weed that is not on the label.
• It has some residual activity. When applied pre-emergent, weeds absorb Tenacity as they emerge from the soil, per the label. The residual is short, which is why the label recommends pairing it with prodiamine (Barricade) for longer pre-emergent control in established turf. Syngenta also says you can seed the same day you spray.
• It is selective, but not universally. The label lists Kentucky bluegrass, tall fescue, fine fescue, perennial ryegrass, centipedegrass, buffalograss, and St. Augustinegrass grown for sod as tested safe, with lower rate caps for ryegrass, fine fescue, and St. Augustine sod. It names bentgrass, Poa annua, kikuyugrass, zoysiagrass, seashore paspalum, and bermudagrass as sensitive. Dormant bermudagrass is the one exception, at a reduced rate. St. Augustine home lawns are not on the label. If you have a southern lawn, this guide is probably not for you.

Tenacity Application Rate (Spot Spray vs Broadcast)

The Tenacity label lists a broadcast rate of 4 to 8 fluid ounces per acre in at least 30 gallons of water. It also caps a single application at 8 fluid ounces per acre and the year at 16 fluid ounces per acre. Almost nobody sprays by the acre at home, so here is the same label math converted to sprayer-friendly rates.

Three more label numbers worth committing to memory. The label says to wait at least 14 days before retreating, and its weed table asks for a second post-emergent spray 2 to 3 weeks after the first. The yearly cap is 16 fluid ounces per acre, which the label spells out as two applications at the maximum single rate. On a per-lawn basis, that is about 2.2 teaspoons per 1,000 square feet per year. If a first pass underwhelmed, check the surfactant and the timing before you touch the rate.

Broadcast amounts by lawn size and grass type

Which column fits your lawn? The label sets the cap by grass. Kentucky bluegrass, tall fescue, centipedegrass, and buffalograss are listed at 5 to 8 fluid ounces per acre. Perennial ryegrass, fine fescue, and any mixed stand over 50 percent of those two stop at 5 ounces. St. Augustinegrass sod stops at 4. The per-1,000-square-foot figures come from the label's own conversion table (0.092, 0.115, and 0.184 fluid ounces), and the rest is multiplication.

The minimum water column is the label's 30 gallons per acre scaled down. Most homeowners spray more water than that, often a full gallon per 1,000 square feet, and that is fine as long as the Tenacity per 1,000 square feet stays the same. Measure how much water your sprayer puts down on a known area first, then add the Tenacity for that area. The spot rate of 0.5 teaspoon per 1,000 square feet works out to about 3.6 fluid ounces per acre, a little under the low broadcast rate, so a spot pass puts down less product per square foot than any broadcast pass on the label.

Tenacity and Surfactant Ratio

The label's spot table pairs 1 teaspoon of Tenacity with 3 teaspoons of non-ionic surfactant (NIS) in a 2-gallon batch. That is 1.5 teaspoons of surfactant per gallon of finished spray, alongside 0.5 teaspoon of Tenacity. You may also see 0.25 percent by volume quoted online, which is about 1.9 teaspoons per gallon. The Tenacity label uses that figure only in its Florida bermudagrass tank-mix directions, so for a home spot spray, 1.5 teaspoons per gallon is the number printed for you. It feels backwards that you add more surfactant than herbicide, but that is exactly what the label intends: the surfactant is the delivery system, and skipping it is one of the most common reasons applications fail. More on why in Step 2 below.

When to apply Tenacity

Tenacity has a wider application window than almost any other selective herbicide on the market, which is part of why it is so useful and also why people get confused about timing. Use this as your decision tree.

Tenacity Application Temperature (Soil and Air Anchors)

The label does not print a temperature range. What it does say is that weed control is most effective on young, actively growing weeds, and that efficacy drops under moisture stress or on mature weeds. So the practical question is whether your weeds and your cool-season grass are both growing well. For most lawns that means daytime highs in the 60s to low 80s with soil that is not bone dry. In cold snaps, weeds grow slowly and take up less product. In heat and drought, cool-season turf is stressed and more likely to whiten. Spring and early fall are the sweet spots. If you are not sure where your soil temp sits, our herbicide timing tool will give you a regional readout.

Is fall a good time to spray Tenacity?

For several of the weeds people buy it for, yes. The label says bentgrass control may be more effective in late summer and early fall than in spring. Purdue Turf puts the most effective ground ivy and violet applications between mid-September and mid-October. Fall is also overseeding season, and that is the window where Tenacity has the fewest substitutes. If your lawn is thin and weedy right now, a fall pass at seeding covers both jobs.

Pre-emergent vs post-emergent

Tenacity does both, but it is far more useful as a post-emergent on established weeds plus a short-window pre-emergent during seeding. The label itself says that in established turf, Tenacity is more effective post-emergent unless it is combined with another soil-active herbicide, and it recommends prodiamine (Barricade) for longer crabgrass and foxtail control. Do not use it alone as your spring crabgrass pre-emergent if you have other options. If you do use it pre-emergent and no rain falls within 10 days, the label says to water in 0.15 inch to activate it.

The killer use case: weed control while overseeding

This is where Tenacity earns its keep. The label allows 5 to 8 fluid ounces per acre (about 0.7 to 1.1 teaspoons per 1,000 square feet) before or after seeding tolerant species: Kentucky bluegrass, tall fescue, and perennial ryegrass, where ryegrass-heavy stands stay at the 5-ounce cap. Fine fescue is the exception. The label says Tenacity may reduce the density of fine fescue seedings and limits seeding use to blends with less than 20 percent fine or hard fescue by weight. Check your seed bag before you spray, since many shade mixes run well over that. Syngenta's overseeding guidance puts the spray the week before, during, or after seeding, and its FAQ says you can seed the same day.

What Does Tenacity Kill?

Syngenta says Tenacity controls more than 46 broadleaf weed and grass species. The ones that matter for most cool-season homeowners:

• On the label post-emergent: creeping charlie (ground ivy), wild violet, white clover, common and mouseear chickweed, henbit, dandelion, oxalis, yellow nutsedge, young crabgrass and goosegrass (the label says under 4 tillers for best control), nimblewill, creeping bentgrass, Canada thistle, and buckhorn plantain.
• Harder in practice: crabgrass past the 4-tiller stage, mature weeds of any kind (the label says efficacy drops on mature weeds), established ground ivy and violet patches that need repeat sprays, and spurge, which is not on the label's weed table.
• Not on the label for control: bermudagrass, dallisgrass, kyllinga, and woody perennials. The weed table also marks annual bluegrass (Poa annua) with no post-emergent control, so Tenacity will not kill plants that are already up.

For crabgrass past the 4-tiller stage, you want quinclorac either as a follow-up or tank-mixed. BASF Drive XLR8 is the quinclorac concentrate I tell homeowners to keep on the shelf for that job. For tough broadleaves like spurge, a 2,4-D ester or a 3-way amine fills the gap.

Does Tenacity kill creeping charlie?

Yes, ground ivy is on the label's post-emergent list. Is it the strongest option, though? Purdue Turf ranks triclopyr first for ground ivy, then fluroxypyr, then 2,4-D, and puts the best timing between mid-September and mid-October. So which one fits your lawn? If you are seeding the same area this fall, Tenacity is the one you can spray at seeding. If you are not seeding, a triclopyr product is the more direct tool for an established patch.

Whichever you choose, set honest expectations. Ground ivy roots at every node, and the label itself calls for a second post-emergent spray 2 to 3 weeks after the first, always with the non-ionic surfactant in the tank. Expect the leaves to whiten first and a slow collapse after that. If a patch survives two proper passes, thicken the turf in that spot too, since thin, shaded, damp areas are exactly where creeping charlie re-invades.

Does Tenacity kill wild violet?

How to apply Tenacity step-by-step

This is where most homeowners go wrong, and it is almost always one of three mistakes: wrong mix rate, no surfactant, or wrong sprayer setup. The label is short and specific. Follow it.

Step 1: Mix rate

For spot spraying with a hand-pump or backpack sprayer:

• 0.5 tsp Tenacity (or generic mesotrione 4SC) per 1 gallon of water covers up to 1,000 sq ft.
• Add 1.5 tsp non-ionic surfactant per gallon (the label's spot table lists 3 teaspoons per 2 gallons).
• Wait at least 14 days between sprays, and stay under 8 fl oz per acre per spray and 16 fl oz per acre per year.

For broadcast applications across a full lawn, the per-acre rate is 4 to 8 fl oz of Tenacity per acre, capped at 5 ounces on ryegrass or fine fescue stands. The lawn-size table above turns that into teaspoons for 1,000 to 10,000 square feet.

Step 2: The surfactant is not optional

This is one of the most common reasons Tenacity "does not work" for first-time users. The label says to apply post-emergent sprays with a non-ionic surfactant. The spray has to get through the waxy surface of the weed leaf. Water alone beads up and rolls off. A non-ionic surfactant (NIS) breaks the surface tension so the spray spreads and sticks.

Methylated seed oil (MSO) works too and is sometimes preferred in cool weather, but it can increase turf sensitivity. For most homeowner applications, plain NIS at the label's 1.5 teaspoons per gallon is the safer call. Southern Ag's non-ionic surfactant is the standard inexpensive option, and a 1-pint bottle makes about 64 gallons of spot mix at that rate.

Step 3: Sprayer setup

Use a hand-pump pressure sprayer or backpack with a flat-fan nozzle that produces medium droplets. Avoid hose-end sprayers and avoid fine-mist nozzles, since drift onto sensitive plants will bleach them too. The label names roses and daylilies as sensitive. Calibrate by spraying a measured amount of clean water across a known area first so you know your gallon truly covers 1,000 sq ft rather than 600 or 1,500.

Step 4: Application

Spray uniformly to wet the leaf surface but stop short of runoff. Walk a steady pace, slight overlap on each pass, and shake the sprayer every couple minutes since mesotrione is a suspension and will settle. Apply when:

• No rain or irrigation is due for at least an hour. Syngenta says Tenacity is rainfast 1 hour after application. The label's surface-water advisory adds that runoff is reduced by not spraying when rain or irrigation is expected within 48 hours, so a dry two-day forecast is the better window, especially on slopes or near a pond or stream.
• The air is calm. The label says to avoid gusty wind, and under 10 mph keeps a hand sprayer's drift in check.
• Weeds are young and actively growing, which for most cool-season lawns means daytime highs in the 60s to low 80s.
• The lawn has not been mowed for 2 to 3 days, and you can wait 2 to 3 days after spraying before mowing again.
• Kids and pets can stay off the area until the spray has dried, which the label calls for.

Step 5: Repeat application

Most weeds need a second pass 2 to 3 weeks after the first, and the label sets 14 days as the minimum gap. Mesotrione is slow by design. Resist the urge to spray sooner just because you do not see results in 4 days. The label says treated weeds stop growing, then turn white, and death may take up to three weeks. The second application catches survivors and any seedlings that emerged since the first. For nimblewill and bentgrass, the label allows up to three sprays at 5 fluid ounces per acre, 2 to 3 weeks apart.

Best Tenacity alternatives and pro-grade companion products

The reality of cool-season weed control is that no single herbicide does everything. Tenacity handles the post-emergent broadleaf and grassy weed work that a 3-way cannot, and it is one of the few options for spraying at seeding, but it has gaps, and the smart move is to keep two or three products on the shelf and pick the right one for each job.

Here is how the Amazon-available stand-ins and companion products stack up.

If you want the 1-gallon professional jug of Syngenta Tenacity rather than the 8-ounce bottle or a generic, SiteOne Landscape Supply carries it, along with Lesco-branded turf products, which are SiteOne-exclusive. For a home lawn, the gallon is far more than you can legally use in a season, so the small bottle or a generic is the practical buy. The active ingredient is what matters, and the generics use the same molecule at the same concentration.

For most homeowner programs, the right combo is a generic or small-bottle mesotrione (your cool-season all-rounder), a non-ionic surfactant (always in the cabinet), and quinclorac for the crabgrass problem you cannot prevent every spring. That three-product kit covers most of the weeds a cool-season lawn throws at you. If you want a deeper read on how to sequence these through the season, our cool-season weed control schedule walks through the full calendar.

Common mistakes with Tenacity

The same handful of mistakes show up over and over in the "Tenacity did nothing" and "Tenacity turned my lawn white" threads. Avoid these and most of the trouble goes away.

Mistake 1: Doubling the rate because "it didn't work"

If your first application didn't kill anything, the likely causes are the surfactant (or lack of one), mature or stressed weeds, or a weed that is not on the label. Doubling the rate raises the odds of whitening your own lawn and can push you past the 8-ounce-per-acre single-spray cap. Stick to 0.5 tsp per gallon per 1,000 sq ft, add the NIS, and wait the full three weeks the label gives for weeds to die before judging results.

Mistake 2: Spraying in cold weather

Weeds that are barely growing take up less herbicide, and the label ties good control to young, actively growing weeds. Spraying during a March warm spell while the soil is still cold usually gives weak, slow results. Wait until the grass and weeds are clearly growing again. The herbicide timing tool gives you a regional read on when that window opens.

Mistake 3: Not knowing your grass type

This is the one that destroys lawns. The label names bermudagrass, zoysiagrass, bentgrass, kikuyugrass, and seashore paspalum as sensitive, and it covers St. Augustine for sod farms only, at a reduced rate. Fine fescue seedings can thin out too. If you are not 100% sure what grass you have, identify it first. Our grass identification tool can confirm before you spray something you cannot undo.

Mistake 4: Stacking applications too close together

The label sets a 14-day minimum between sprays and a 16-ounce-per-acre yearly cap. People who spray every weekend "to be sure" blow through that cap and end up with persistent turf whitening. The label also notes that a repeat spray on the same site causes less whitening than the first, so a properly spaced second pass is gentler than people expect. Trust the chemistry and wait.

Mistake 5: Skipping the second application

The flip side of mistake 4. The label says a repeat application is required after two to three weeks for improved post-emergent control, and tough weeds like creeping charlie and nimblewill rarely finish after one pass. The second pass catches survivors and seedlings that emerged since the first. Plan on two applications from the start.

Mistake 6: Spraying right before or after mowing

Both are bad. Spraying right before mowing means you cut off the treated leaf tissue before mesotrione moves through the plant. Spraying right after mowing means weeds have minimal leaf surface to absorb the spray. Aim for 2 to 3 days of growth before spraying and 2 to 3 days of waiting after.

Mistake 7: Using a hose-end sprayer

Hose-end sprayers cannot deliver the precise per-1,000-sq-ft rate Tenacity needs. They also produce coarse, uneven coverage. Use a hand-pump pressure sprayer for under 5,000 sq ft, a 4-gallon backpack for anything larger.

Mistake 8: Putting treated clippings in the garden

Where do your clippings go? The label says not to use grass clippings from treated turf as mulch around trees or in vegetable or flower gardens, and not to plant any crop other than turfgrass in a treated area for 18 months. If you are turning a sprayed corner of the lawn into a vegetable bed next spring, that 18-month clock matters. One more label rule that catches people: do not apply an organophosphate or carbamate insecticide within seven days of a Tenacity spray, or the turf may be injured.

Mesotrione is one of the most effective tools in cool-season lawn care, and it rewards homeowners who measure carefully. Get the rate right, always include the surfactant, mind the soil temperature, and pair it with quinclorac when you need to finish off mature crabgrass. The white grass scare goes away once you understand the bleaching is the kill signal, and the lawn that comes back is cleaner than anything a 3-way alone can deliver.