UGLY CLUMP GRASS KILLER IN LAWNS
Coarse Fescue, Native Grass, and Brome Grass Control
Is There a Way to Kill These Ugly Grasses in the Lawn?
Common perennial grasses that invade lawns include coarse fescue, smooth brome, field grasses, and other native varieties. These thick-bladed grasses disrupt lawn uniformity, leaving many homeowners wondering how if there is an “effective ugly grass control” that won’t damage their desirable turf.
Yes There is a Way to Control these Grasses!
For years, controlling tall fescue and other coarse grasses was challenging, requiring non-selective herbicides like glyphosate, which kill all vegetation on contact—resulting in large, unsightly brown patches that demand reseeding or sodding. Fortunately, a game-changing solution is now available: Tenacity. This selective herbicide effectively targets coarse-bladed grasses without harming desirable turf, making it an excellent choice for restoring a lush, uniform lawn with minimal disruption.
This is Unimporved Coarse Fescue
(A Perennial Grass)
(Click on Image to Enlarge)
How to Tell the Difference Between Crabgrass and Other Clump Grasses
Are those unsightly clumps of grass in your lawn crabgrass? It’s unlikely—but you can easily find out. If the grass started sprouting in June, it is likely an annual weed, such as crabgrass. However, if it has been thriving year-round, it is most likely a perennial grass, not crabgrass.
How to Tell the Difference Between Crabgrass and Other Clump Grasses
Crabgrass is one of the easiest grassy weeds to control when treated with Drive XLR8. Unlike other invasive clump grasses that require multiple treatments, Drive XLR8 eliminates crabgrass with just one application when applied correctly. It works by penetrating the weed’s tissue, stopping its growth, and ultimately killing it at the root. For best results, apply Drive XLR8 when crabgrass is young and actively growing, typically in mid-summer. This fast-acting solution helps restore your lawn’s uniformity without the need for excessive retreatments, making crabgrass control quick, effective, and hassle-free.
This is Crabgrass
(An Annual Grass)
(Click on Image to Enlarge)
Perennial Clump Grasses Are Now Controllable
Three Consecutive Applications
Back-to-Back-to-Back Sprays
To effectively address those unsightly grasses in your lawn, consider the powerful solution of back-to-back-to-back applications of Tenacity, a specialized weed control product. Our experience shows that this approach can achieve an impressive control rate of 50-90% or even higher. The most significant results are often seen with grasses that resemble field grasses, while grasses more akin to turfgrass yield lower control rates. This occurs because turf-like grasses are frequently hybrids of improved turfgrass and native grass. Since Tenacity is non-toxic to improved turfgrasses, these hybrids are less likely to be effectively managed.
Applications are Spaced 7-12 Days Apart
The treatment process involves three applications spaced about 7-12 days apart. Our technician will carefully spot spray the unwanted clumps in your lawn, and by the second application, you’ll likely notice the grasses starting to turn white. The third application will ensure their demise, allowing desirable grasses to reclaim the space in the following weeks.
We Treated the Left Side
A Very Unique Herbicide
What sets Tenacity apart is its unique formulation containing mesotrione, a synthetic herbicide recognized for its effectiveness. While mesotrione originates from a naturally occurring compound in the bottlebrush plant, its commercial formulation classifies it as a synthetic chemical. However, if it were directly extracted from the plant, it would be considered organic.
Why Does Tenacity Turn Plants White?
Mesotrione functions by inhibiting the enzyme HPPD, crucial for photosynthesis. It also halts carotenoid formation in susceptible plants, leading to the destruction of chlorophyll and cell membranes. This process causes the grass to turn white, ultimately resulting in its death. Within just 2-3 weeks after application, you’ll start to see the stark contrast with white blades appearing, signaling the beginning of a healthier lawn. Don’t let these unsightly grasses take over—opt for Tenacity and watch your lawn transform!
White Means the Weed Control is Working
Ugly Clump Grass Killer for Lawns
Will My Clump Grass Die?
Due to the large number of grass varieties, we cannot guarantee control over all fescues and other grasses. However, we have observed that the closer the grass resembles field grass, the better control we achieve.
We Only Treat the Large Clumps
This treatment is designed as a spot spray for targeting a few clumps of unwanted grass within an existing lawn. However, for lawns that are heavily infested with these grasses, it’s important to set realistic expectations. In cases where the lawn is completely overrun, we recommend a more effective approach: removing the entire lawn and starting fresh, rather than attempting to reclaim it with spot treatments.
If you have coarse tall fescue, brome or pasture grasses growing in your Boulder or Fort Collins area lawn, call Organo-Lawn today and schedule an application to kill those grasses.
Less Likely to be Controlled
More Likely to be Controlled
Tenacity Pesticide Fact Sheets
Application Season
Anytime that the grass is actively growing. This can be as early as April to the end of September.
Tenacity Pesticide Fact Sheets
Coarse Fescue, Native Grass, and Brome Treatment Information Sheets
Tenacity herbicide is registered with the EPA by BASF, EPA reg. #100-1267.
This post-emergent coarse fescue treatment is also registered with the Colorado Department of Agriculture.
Schedule a Ugly Clump Grass Killer for Lawns
(303) 499-2000 in Boulder or (970) 225-9425 in Fort Collins.
Ugly Clump Grass Killer FAQ's
Why Coarse Fescue and Brome Grass Are Difficult to Control in Bluegrass Lawns
Similar Growth Habits to Desirable Turf
Coarse fescue and brome grass are perennial grasses, meaning they return year after year, unlike annual grassy weeds such as crabgrass. Their biology closely resembles that of Kentucky bluegrass (KBG), making them harder to distinguish and eliminate with a single treatment.
Deep Roots and Resilient Growth Structure
- Coarse fescue develops thick, deep roots, allowing it to withstand drought, poor soil conditions, and stress better than KBG.
- Brome grass spreads through rhizomes (underground stems), enabling it to regenerate even after mowing or surface treatments, making complete removal challenging.
Limited Selective Herbicide Options
- Most broadleaf herbicides (like 2,4-D) are ineffective because they only target broadleaf weeds (dicots), not grassy weeds (monocots).
- Non-selective herbicides (like glyphosate) kill all vegetation, including desirable bluegrass, making them impractical for widespread use.
- Tenacity (mesotrione) can suppress coarse fescue and brome grass, but multiple applications are often required for effective control.
Unlike common broadleaf weeds such as dandelions, which have numerous treatment options, there are very few selective herbicides that can specifically target coarse fescue or brome grass without damaging Kentucky Bluegrass. This makes their control particularly difficult in established bluegrass lawns.
Clump Grass Spot Spray
Additional Ugly Clump Grass Control FAQs
We typically apply Tenacity as a spot treatment only in the problem areas. If a lawn is very large we may do a spray tank application to save time, but the majority of the properties are spot treated using a backpack sprayer.
Tenacity can be applied any time these ugly grasses are actively growing.
The label states to stay off the lawn until the application is dry. We recommend staying off treated areas for 24 hours to be extra cautious.
Tenacity is rain proof within 30 minutes of the application. If it does rain within 30 minutes of an application please contact our office. If it does not work after the third application please contact our office and we will apply the product again, free of charge.
The active ingredient in Tenacity herbicide is mesotrione.
How Mesotrione Works
- Mesotrione is a selective, systemic herbicide that inhibits the HPPD enzyme (4-Hydroxyphenylpyruvate dioxygenase) in plants, preventing the production of essential pigments for photosynthesis.
- This causes susceptible plants to turn white (bleaching effect) as they lose chlorophyll and eventually die.
- It is effective for both pre-emergent and post-emergent control of certain broadleaf and grassy weeds in cool-season turf.
Legally we cannot answer this safety question because it is an EPA registered pesticide. We can however, tell the customer that the EPA’s signal word on Drive is Caution, which is the lowest of the three signal words. Danger is the highest toxicity, then Warning, and the lowest level of toxicity is Caution.
- “Caution” – Low toxicity (least hazardous)
- “Warning” – Moderate toxicity
- “Danger” – High toxicity or potential for severe eye/skin damage
- “Danger – Poison” – Highly toxic (lethal in small amounts)
Tenacity (mesotrione) is on the EPA’s Reduced Risk Pesticide List
What Does “Reduced Risk” Mean?
The EPA (Environmental Protection Agency) grants Reduced Risk status to pesticides that:
- Pose lower toxicity to humans and animals compared to conventional alternatives.
- Have less environmental impact, including reduced risks to water sources and non-target organisms.
- Provide effective pest control while being safer for beneficial organisms.
Why is Tenacity Considered Reduced Risk?
- Lower toxicity to humans and pets when used correctly.
- Breaks down quickly in soil, reducing long-term environmental persistence.
- Less impact on beneficial insects and wildlife compared to many older herbicides.
Tenacity herbicide works by inhibiting the HPPD enzyme (4-Hydroxyphenylpyruvate dioxygenase), which is essential for photosynthesis in plants.
How It Works:
- Blocks Carotenoid Production – Mesotrione disrupts the synthesis of carotenoids, which are pigments that protect chlorophyll in plants.
- Leads to Chlorophyll Breakdown – Without carotenoids, chlorophyll degrades, causing affected plants to lose their green color.
- Visible Whitening Effect – Weeds turn white (bleached) because they cannot produce new chlorophyll.
- Stops Photosynthesis – Without chlorophyll, the plant cannot produce energy, leading to slow death over 2-3 weeks.
No, Tenacity (mesotrione) is not considered organic, but it is as close to organic as a synthetic herbicide can be. Here’s why:
Tenacity’s active ingredient, mesotrione, is derived from a naturally occurring compound found in the bottlebrush plant (Callistemon citrinus). However, rather than being harvested directly from the plant, mesotrione is chemically synthesized for commercial production.
If the mesotrione used in Tenacity were extracted from the bottlebrush plant instead of replicated in a lab, it could qualify as an organic product. The key distinction is how the ingredient is sourced—it mirrors a natural compound but is lab-synthesized rather than plant-extracted, making it synthetic rather than organic under certification standards.
Expected Results After Applying Tenacity (Mesotrione)
1st Application – No immediate visual changes will be noticeable. The herbicide begins working internally to disrupt pigment production.
2nd Application – Slight discoloration or whitening may start appearing on the target grasses, indicating the herbicide is taking effect.
3rd Application – Significant whitening of the target grasses should be evident, signaling continued disruption of chlorophyll production.
Over the next 20 to 60 days, the affected grasses will gradually turn completely white and die off. In some cases, it may take up to two months for the entire plant to decompose and disappear from the lawn.
Typically, 3 applications each spaced 7-14 days apart are required for effective control. Coarse fescue may take multiple treatments to fully die off.
Tenacity inhibits the production of photosynthetic pigments in coarse fescue, causing it to turn white and eventually die. It selectively affects unwanted grass species while being safe for certain desirable turfgrasses.
For stubborn coarse fescue patches, the only treatment option will be to spot treat using a non-selective control like glyphosate. If this technique is used it is recommend to follow up by overseeding with desirable turfgrasses to fill in the bare areas.
It takes at least 14 days after the first application for discoloration to appear in coarse grasses. They will turn white before dying.