Weed Identification for Warm-Season Turf
Why this matters
Warm-season turf (bermudagrass, zoysia, St. Augustine, centipede, bahia) is dominant in the southern US, southwestern, and southeastern states. The weed pressure is different from cool-season turf, and so are the herbicides. Specifically, several herbicides safe for Kentucky bluegrass kill St. Augustinegrass or bermuda; some herbicides safe for bermuda damage centipedegrass. A contractor who knows the specific turf type and the appropriate weed-control approach for that turf produces effective treatment without lawn damage. The classic failure: a tech with Kentucky bluegrass habits applies 2,4-D + dicamba at standard rate to a St. Augustinegrass lawn and kills the lawn along with the weeds.
Warm-season turf types
| Turf type | Region | Salt tolerance | Shade tolerance | Wear tolerance |
|---|---|---|---|---|
| Bermudagrass | Lower south, central south | Low | Low | Excellent |
| Zoysia | Mid south to upper south | Low | Moderate | Excellent |
| St. Augustinegrass | Coastal south, FL, TX | High | High | Moderate |
| Centipedegrass | Deep south, GA, SC | Low | Low | Low |
| Bahiagrass | FL, southern GA | Low | Low | Excellent |
| Buffalograss | Plains, southwest | Low | Low | Moderate |
| Seashore paspalum | Coastal areas | Excellent | Low | Excellent |
Each turf type has specific herbicide tolerances. Verify the turf type before any herbicide application.
Common warm-season turf weeds
Annual grassy weeds
Crabgrass (Digitaria sanguinalis, D. ischaemum)
- Same as cool-season; major weed in warm-season too
- Control: pre-emergent in late winter / early spring; post-emergent with quinclorac, MSMA (where allowed)
Goosegrass (Eleusine indica)
- Same as cool-season
- Control: oxadiazon pre-emergent; post-emergent harder
Crowfoot grass (Dactyloctenium aegyptium)
- Annual; common in lower south
- Control: same as crabgrass
Perennial grassy weeds
Dallisgrass (Paspalum dilatatum)
- Coarse-textured perennial; clumping; major weed in southern lawns
- Damage: visible texture difference; persistent
- Control: MSMA (where allowed), DSMA, glyphosate spot treatment + reseed
Bahiagrass invading bermuda lawns
- Coarse texture; spreads rapidly
- Control: similar to dallisgrass; spot treatment
Common bermuda invading St. Augustinegrass
- The common bermuda is often a weed in St. Augustine lawn
- Control: fluazifop (Fusilade) selective against bermuda but safe on St. Augustine
Annual broadleaf
Common chickweed: same as cool-season
Henbit: same as cool-season
Florida pusley (Richardia scabra): small white flowers; common in FL
- Control: standard broadleaf
Perennial broadleaf
Doveweed (Murdannia nudiflora)
- Spreading low-growth plant; small purple flowers
- Aggressive in St. Augustine and centipede
- Control: atrazine (on St. Augustine and centipede); imazaquin
Virginia buttonweed (Diodia virginiana)
- Spreading low-growth; small white flowers
- Difficult to control in St. Augustine
- Control: metsulfuron (Manor); multiple applications
Penny wort / dollarweed (Hydrocotyle umbellata)
- Round leaves with center stem (umbrella-like)
- Wet area indicator; thrives in saturated soil
- Control: address moisture first; atrazine or imazaquin
Beggarweed (Desmodium tortuosum)
- Trifoliate leaflets; small pink flowers
- Control: standard broadleaf
Wild garlic / wild onion
- Same as cool-season; bulb-based perennial
- Control: standard broadleaf; multiple applications
Sedges
Yellow nutsedge, purple nutsedge
- Same as cool-season; common in warm-season too
- Control: sulfentrazone, halosulfuron
Globe sedge (Cyperus globulosus)
- Common in lower south
- Control: same as nutsedge
Lower-southern specific
Lippia (Phyla nodiflora)
- Low-growing perennial; small purple flowers
- Sometimes intentional groundcover (pollinator value)
- Control: triclopyr if undesirable
Torpedograss (Panicum repens)
- Aggressive perennial grass with horizontal rhizomes
- Damage: very difficult to control; takes over
- Control: limited herbicide options; spot treatment with glyphosate then reseed
Herbicide categories for warm-season turf
Pre-emergent
- Prodiamine, dithiopyr, pendimethalin: same as cool-season
- Application timing: late winter to early spring (before soil reaches 55 F)
- Some applications also recommended in late summer / early fall
Post-emergent broadleaf
- 2,4-D + dicamba: caution; reduced rate on St. Augustine and centipede
- Atrazine: SAFE on St. Augustine and centipede; not for bermuda or zoysia
- Imazaquin (Image): for St. Augustine and centipede
- Metsulfuron (Manor): for St. Augustine; very low rate
- Triclopyr: caution; can damage St. Augustine if rate too high
Post-emergent grass
- Quinclorac: for crabgrass; SAFE on bermuda and zoysia; NOT for St. Augustine or centipede
- MSMA (where still allowed): for crabgrass, dallisgrass; restricted in many states
- Fenoxaprop (Acclaim): selective against grass weeds
Post-emergent sedge
- Halosulfuron, sulfentrazone: same as cool-season; verify turf compatibility
Specific to St. Augustine and centipede
- Atrazine: useful for both broadleaf weeds and some grasses
- Imazaquin: for various broadleaf
- Sethoxydim: for grass weeds
Turf-specific herbicide caution
| Herbicide | Bermuda | Zoysia | St. Augustine | Centipede |
|---|---|---|---|---|
| 2,4-D + dicamba (standard rate) | OK | OK | Reduced rate only | Reduced rate only |
| Atrazine | NOT for bermuda | NOT for zoysia | OK | OK |
| Quinclorac | OK | OK | NOT | NOT |
| MSMA | OK | OK (caution) | NOT | NOT |
| Triclopyr (standard) | OK | OK | Caution | Caution |
| Imazaquin | Caution | Caution | OK | OK |
| Metsulfuron | NOT for bermuda | NOT for zoysia | OK (low rate) | NOT |
Verify against the specific herbicide label and the turf manufacturer's tolerance data.
Identification by visible characteristic
| Visual characteristic | Likely weed |
|---|---|
| Spreading, low-growth, small flowers | Doveweed, lippia, virginia buttonweed |
| Coarse texture in fine-textured lawn | Bermuda in St. Augustine, dallisgrass in any |
| Tall coarse upright grass | Dallisgrass, bahiagrass |
| Round umbrella-shaped leaves | Pennywort / dollarweed |
| Triangular stem | Sedge |
| Trifoliate leaves | Clover, oxalis, beggarweed |
| Tubular leaves with bulb base | Wild garlic / onion |
Mowing and weed competition
Higher mowing height typically reduces weed pressure:
- Crabgrass and goosegrass: lower mowing favors them
- St. Augustinegrass: maintain at 3.5 to 4.5 inches (high)
- Bermuda: 1 to 1.5 inches (close)
- Zoysia: 1 to 2 inches
- Centipede: 1.5 to 2 inches
References
- USGA Green Section publications.
- LSU AgCenter, University of Florida IFAS, Texas A&M AgriLife turf weed control guides.
- North Carolina State Extension turf weed management.
- USDA Cooperative Extension Service warm-season turf guidance.
- Manufacturer labels for specific herbicides.
- Manuall internal: LawnCare Common Lawn Weeds, LawnCare Weed ID and Control, LawnCare Grass Selection by Climate.