What's in this guide

  1. Why Grass Type Matters
  2. Full Compatibility Chart
  3. Bermuda Grass
  4. Zoysia Grass
  5. St. Augustine Grass
  6. Centipede Grass
  7. Kentucky Bluegrass
  8. Tall & Fine Fescue
  9. Perennial Ryegrass
  10. FAQ

Why Your Grass Type Is the #1 Factor

Every herbicide label lists which grasses it's safe on — but most homeowners skip this section and just spray. The result can be permanent damage to your lawn that takes months to recover.

The most dangerous mismatches involve warm-season grasses (St. Augustine, Centipede, Zoysia) and commonly used herbicides. Many products safe on Kentucky Bluegrass will bleach or stunt warm-season varieties. The key culprits are atrazine (fine on St. Augustine, toxic to most others) and 2,4-D at high rates (damages St. Augustine and Centipede).

Warm Season grasses — Bermuda, Zoysia, St. Augustine, Centipede, Bahia. Active in summer. Most sensitive to triclopyr and dicamba at high rates.
Cool Season grasses — Kentucky Bluegrass, Fescue, Ryegrass, Bentgrass. Active spring/fall. Broadest herbicide tolerance. Most Canadian lawns fall here.
Mixed Transition zone lawns (Virginia to Kansas) may have both types. Test a small area first. When in doubt, use the safer rate listed on the label.
⚠️
Always patch-test first

Even when a product is listed as "safe" for your grass type, apply to a 2 sq ft test area and wait 7 days before treating the full lawn. Environmental stress, new seeding, drought, or disease can increase sensitivity to herbicide damage.

Full Herbicide × Grass Type Compatibility Chart

✓ = Safe at label rate  |  ⚠ = Use caution / reduced rate  |  ✕ = Avoid / will damage  |  — = Not applicable

Herbicide / Active Bermuda Zoysia St. Augustine Centipede KY Bluegrass Fescue Ryegrass
2,4-D (standard rate) ✓ ✓ ⚠ ⚠ ✓ ✓ ✓
MCPP (Mecoprop) ✓ ✓ ⚠ ✕ ✓ ✓ ✓
Dicamba ✓ ⚠ ✕ ✕ ✓ ✓ ✓
Quinclorac (crabgrass) ✓ ✓ ✓ ✕ ✓ ✓ ✓
Triclopyr ⚠ ✕ ✕ ✕ ✓ ✓ ✓
Atrazine ✕ ✕ ✓ ✓ ✕ ✕ ✕
Prodiamine (pre-emergent) ✓ ✓ ✓ ✓ ✓ ✓ ✓
Imazaquin (nutsedge) ✓ ✓ ✓ ⚠ ✕ ✕ ✕

Bermuda Grass Weed Killers

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Bermudagrass
Cynodon dactylon · Warm-season · Southeast, Southwest USA, transition zone
Warm Season

Bermuda is one of the most herbicide-tolerant warm-season grasses, which makes weed control significantly easier than St. Augustine or Centipede. Most broadleaf herbicide blends are safe at standard rates, and it handles quinclorac for crabgrass control without issue.

✓ Safe Products
  • Roundup for Lawns (Bermuda) — 2,4-D + MCPP + Dicamba + Quinclorac. Handles broadleaf and crabgrass in one product.
  • Ortho Weed B Gon Chickweed, Clover & Oxalis Killer — Triclopyr-based. Use with caution; safe at label rate on dormant Bermuda.
  • Prodiamine / Barricade — Excellent pre-emergent for annual grassy weeds. Safe on all Bermuda.
  • Quinclorac (Drive XLR8) — Post-emergent crabgrass killer. Fully safe on Bermuda.
  • Tenacity (mesotrione) — Safe on Bermuda for nutsedge and broadleaf control.
✕ Avoid / Use Caution
  • Atrazine — Will kill or severely damage Bermuda grass. Not registered for Bermuda use.
  • Triclopyr at high rates (actively growing) — Can cause temporary bleaching on actively growing Bermuda in summer. Use on dormant grass only if required.
  • MSMA — Restricted use in many states. Can damage Bermuda if over-applied.
Pro Tip for Bermuda Bermuda goes dormant (turns brown) in winter in many regions. You can apply triclopyr-based products to control winter weeds during dormancy without damaging the grass — a popular technique in the Southeast.

Zoysia Grass Weed Killers

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Zoysiagrass
Zoysia spp. · Warm-season · Southeast USA, transition zone
Warm Season

Zoysia is moderately sensitive to herbicides — more tolerant than St. Augustine, but more sensitive than Bermuda. Dicamba and triclopyr at high rates are the main concerns. Stick to lower labeled rates and avoid application during heat stress above 90°F.

✓ Safe Products
  • 2,4-D (low rate) — Safe for broadleaf control. Use the lowest labeled rate; avoid summer applications.
  • Quinclorac (Drive XLR8) — Crabgrass control. Safe on Zoysia at label rate.
  • Prodiamine / Barricade — Best pre-emergent option. Fully safe.
  • Roundup for Lawns (Zoysia formula) — Check label for Zoysia-specific formula or rate.
✕ Avoid / Use Caution
  • Triclopyr — Can cause significant injury on Zoysia. Avoid entirely during active growth.
  • Dicamba (high rate) — Use caution; lower rates typically safe but risk of injury exists on stressed lawns.
  • Atrazine — Not registered for Zoysia. Will cause damage.
  • Imazaquin — Some formulations cause temporary injury. Check label carefully.
Pro Tip for Zoysia Zoysia grows slowly and recovers poorly from herbicide damage. When in doubt, spot-treat with a paint-on gel formulation rather than broadcasting across the full lawn. Glyphosate-based products will kill Zoysia — never use non-selective herbicides for spot treatment.

St. Augustine Grass Weed Killers

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St. Augustinegrass
Stenotaphrum secundatum · Warm-season · Florida, Gulf Coast, Hawaii
Warm Season

St. Augustine is the most herbicide-sensitive common lawn grass. Many products that work perfectly on other grasses will cause severe, lasting damage here. This is the most critical grass type to get right. Atrazine is one of the few herbicides specifically registered for St. Augustine — a complete reversal from other grass types.

✓ Safe Products
  • Atrazine (Spectracide Weed Stop for St. Augustine) — One of the few herbicides specifically safe on St. Augustine. Controls many broadleaf weeds. Not safe on any other grass type.
  • 2,4-D at reduced rate (50% label rate) — Use with caution. Avoid in heat. Some St. Augustine cultivars are sensitive even at reduced rates.
  • Quinclorac — Safe for crabgrass control on St. Augustine.
  • Prodiamine (pre-emergent) — Safe for annual weed prevention. Apply in early spring.
✕ Avoid These Completely
  • Dicamba — Will cause severe, lasting injury. Do not use.
  • Triclopyr — Causes bleaching and dieback on St. Augustine. Avoid entirely.
  • MCPP (Mecoprop) — Known to injure St. Augustine. Avoid products containing MCPP.
  • Most three-way broadleaf blends (2,4-D + MCPP + Dicamba) — Avoid. The MCPP and Dicamba components will damage your lawn.
Critical Warning for St. Augustine Owners The most common and most damaging mistake: using a standard three-way broadleaf killer (2,4-D + MCPP + Dicamba) on St. Augustine. The MCPP and Dicamba components cause serious, often irreversible damage. Always verify the label says "safe for St. Augustinegrass" specifically.

Centipede Grass Weed Killers

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Centipedegrass
Eremochloa ophiuroides · Warm-season · Southeast USA, low-fertility soils
Warm Season

Centipede is nearly as sensitive as St. Augustine. It's a low-maintenance, low-fertility grass that is easily stressed by over-application of any chemical. The safest approach is atrazine for broadleaf and prodiamine for prevention. Avoid quinclorac and most three-way blends.

✓ Safe Products
  • Atrazine — Best broadleaf option for Centipede. Specifically registered. Apply at label rate only.
  • Prodiamine (pre-emergent) — Best prevention option. Fully safe on Centipede.
  • 2,4-D (reduced rate only) — Only at 50% of label rate. Never in summer heat. Stress increases sensitivity.
✕ Avoid / High Risk
  • Quinclorac — Known to cause severe injury on Centipede. Avoid for crabgrass control — use pre-emergent instead.
  • Dicamba, MCPP, Triclopyr — All cause significant injury. Avoid entirely.
  • High-nitrogen fertilizer + herbicide combos — Centipede is very sensitive to excess nitrogen. Never use weed-and-feed products.

Kentucky Bluegrass Weed Killers

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Kentucky Bluegrass
Poa pratensis · Cool-season · Northern USA, Canada, transition zone
Cool Season

The most common Canadian lawn grass and dominant in the northern US. Kentucky Bluegrass has excellent herbicide tolerance and can handle all standard broadleaf killers, three-way blends, and crabgrass herbicides at full label rates. This is the easiest grass type for weed control.

✓ Safe Products
  • Killex Concentrate (Canada) — 2,4-D + MCPP + Dicamba. Ideal for Canadian Bluegrass lawns. Our top-rated choice.
  • Weed B Gon Lawn Weed Killer — Same three-way formula. Fully safe at label rate.
  • Roundup for Lawns — Adds quinclorac for crabgrass. Safe on Bluegrass.
  • Prodiamine / Barricade (pre-emergent) — Excellent for crabgrass prevention. Fully safe.
  • Triclopyr (for ground ivy, wild violet) — Safe on Kentucky Bluegrass. Best for tough-to-kill broadleaf weeds.
✕ Avoid
  • Atrazine — Will damage or kill Kentucky Bluegrass. Strictly a warm-season grass product.
  • Any herbicide above label rate — Though tolerant, over-application causes temporary yellowing and stress.
  • Application to newly seeded areas — Wait until lawn has been mowed 3–4 times before any herbicide use.
Canadian Lawn Owners Most Canadian lawns are Kentucky Bluegrass or Bluegrass/Fescue blends. Killex Concentrate is the best-value Canadian product for this grass type. See our full Killex review for detailed results.

Tall & Fine Fescue Weed Killers

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Tall Fescue & Fine Fescue
Festuca arundinacea / Festuca spp. · Cool-season · Northern US, Canada, shade lawns
Cool Season

Fescues are among the most herbicide-tolerant cool-season grasses. They handle all standard three-way broadleaf herbicides well. The main caveat: Creeping Red Fescue (used in shade mixes) is somewhat more sensitive than Tall Fescue and should be treated at lower rates during heat stress.

✓ Safe Products
  • 2,4-D + MCPP + Dicamba blends — Fully safe on all Fescue varieties at standard rates.
  • Quinclorac — Crabgrass control. Safe on Tall and Fine Fescue.
  • Prodiamine (pre-emergent) — Best prevention. Fully safe.
  • Triclopyr — Safe for tough broadleaf weeds (wild violet, ground ivy). Use full label rate on Tall Fescue; reduce by 25% on Fine Fescue.
✕ Use Caution
  • Atrazine — Not registered for Fescue. Will cause damage.
  • High-rate dicamba on Creeping Red Fescue — Reduce rate by 25% on fine-textured Fescue varieties in shade or stressed conditions.

Perennial Ryegrass Weed Killers

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Perennial Ryegrass
Lolium perenne · Cool-season · Northern USA, Canada, overseeding
Cool Season

Perennial Ryegrass is commonly found in lawn mixes alongside Kentucky Bluegrass and Fescue. It has very similar herbicide tolerance to Kentucky Bluegrass — tolerating standard three-way broadleaf blends and quinclorac-based products well at full label rates.

✓ Safe Products
  • 2,4-D + MCPP + Dicamba blends — Fully safe at label rate. Same tolerance as Kentucky Bluegrass.
  • Quinclorac — Safe for crabgrass control on Perennial Rye.
  • Prodiamine (pre-emergent) — Safe. But avoid applying when overseeding.
✕ Avoid
  • Atrazine — Not registered for Ryegrass. Will cause damage.
  • Application within 4 weeks of overseeding — Pre-emergents block seed germination. Post-emergents damage young seedlings. Time applications carefully.

Frequently Asked Questions

The easiest method: look at your lawn in late summer. If it stays green and thick, you likely have a cool-season grass (Fescue, Bluegrass, Ryegrass). If it goes dormant and turns brown in winter, it's likely warm-season (Bermuda, Zoysia, St. Augustine, Centipede). For more precise identification, check your local university cooperative extension — most have free grass ID resources by state. You can also bring a sample to your local garden center.
Yes — in most cases. Kentucky Bluegrass and Fescue have essentially identical herbicide tolerance. Any product safe on Bluegrass is also safe on Fescue, with the minor exception of reducing the rate slightly on Creeping Red Fescue (a fine-textured variety often found in shade mixes). Standard three-way broadleaf blends (2,4-D + MCPP + Dicamba) are safe on all common Bluegrass/Fescue/Ryegrass combinations.
Atrazine-based products (like Spectracide Weed Stop for St. Augustinegrass or Southern Ag Atrazine) are the safest and most effective option. This is one of the only grass types where atrazine is the recommended choice rather than a 2,4-D-based product. For crabgrass, quinclorac is safe on St. Augustine. Avoid any product containing MCPP, dicamba, or triclopyr on St. Augustine lawns.
Killex (2,4-D + MCPP + Dicamba) is primarily designed for cool-season grasses common in Canada — Kentucky Bluegrass, Creeping Red Fescue, and Perennial Ryegrass. On warm-season grasses, the MCPP and Dicamba components can cause injury, particularly on St. Augustine and Centipede. Bermuda handles Killex better than the others, but it's still worth using a Bermuda-specific product in the southern US.
For cool-season grasses: optimal range is 60–80°F (15–27°C). Above 85°F increases risk of grass injury. For warm-season grasses: treat during active growth (above 70°F), but avoid application when air temps are above 90°F and the lawn is already heat-stressed. Regardless of grass type, never apply to a frost-stressed or drought-stressed lawn — the risk of damage increases significantly.

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