Prostrate Knotweed (Polygonum aviculare): Identification & Selective Herbicide Matrix
Quick Agronomic Summary
SpeedZone (Carfentrazone + 2,4-D + Dicamba) kills Prostrate Knotweed in spring while plants are young.
- Diagnostic Marker 1: Wiry, prostrate stems forming tough circular mats in heavily trampled, compacted turf
- Diagnostic Marker 2: Small, dull blue-green oblong leaves with papery sheaths (ochrea) at each swollen stem joint
- Diagnostic Marker 3: Inconspicuous tiny pinkish-white flowers clustered in leaf axils
What herbicide kills Prostrate Knotweed?
SpeedZone (Carfentrazone + 2,4-D + Dicamba) kills Prostrate Knotweed in spring while plants are young.
Once Knotweed stems mature and turn wiry in summer, they become highly resistant to post-emergents. Pre-emergent Prodiamine applied in early spring prevents emergence.
When to spray Prostrate Knotweed?
Apply post-emergents in early spring when seedlings first emerge along compacted sidewalk edges.
Core aerating compacted soil eliminates the environmental niche knotweed exploits.
EPA-Registered Herbicides Labeled for Prostrate Knotweed
The table below compares all selective herbicides in our database that control Prostrate Knotweed, including active ingredient groups, application temperature limits (°F), and surfactant requirements.
| Brand Name & EPA Reg. | Active Ingredient & WSSA Group | Temp Window (°F) | Surfactant & Mixing Protocol | Where to Buy |
|---|---|---|---|---|
| SpeedZone Lawn Weed Killer EPA Reg. 2217-833 |
2,4-D 28.57%, Mecoprop-p 5.88%, Dicamba 1.71%, Carfentrazone-ethyl 0.62% Group 4 + Group 14 (Synthetic Auxins + PPO Inhibitor) |
50°F – 85°F Rainfast: 3h |
Do NOT add surfactant. Adding NIS or MSO increases ester volatility and causes severe contact burn on desirable cool-season turf. | Check Price at DoMyOwn View on Amazon |
| Barricade 4FL (Prodiamine 65 WDG) EPA Reg. 100-1139 |
Prodiamine 40.7% (or 65% WDG) Group 3 (Microtubule Assembly Inhibitor / Dinitroaniline) |
45°F – 90°F Rainfast: 0h |
Pre-emergent soil barrier: do NOT use foliar surfactant. Must be watered in with 0.5 inches of irrigation or rainfall within 14 days of application to activate. | Check Price at DoMyOwn View on Amazon |
Turfgrass Compatibility Matrix for Prostrate Knotweed Herbicides
Always verify that your chosen herbicide is safe for your specific lawn grass before broadcast spraying:
How to Distinguish Prostrate Knotweed from Lookalike Weeds
| Lookalike Species | Key Botanical & Diagnostic Difference |
|---|---|
| Spotted Spurge | Spotted spurge emits white milky sap when severed; knotweed has wiry stems with papery joint sheaths and clear sap. |