Fall Lawn Weed Control: When to Spray Broadleaf Weeds Before Winter

Fall is the season to treat perennial broadleaf weeds such as dandelion, clover, wild violet and creeping Charlie. Here is why fall works, how late you can spray in your zone, what warm-season lawns need instead, and a spray-day checklist.

Why fall works best

• In early fall “weeds send more of their resources to the roots to prepare for winter survival” (SDSU Extension).
• “A fall-applied herbicide will enter the plant and travel to these plant parts with the food reserves” (Colorado State Extension).
• For “perennial broadleaf weeds like dandelion, early to mid-fall is the recommended window for spraying,” and “Spring and early summer applications may not provide as good of control as fall.” In fall, cool-season lawns “readily fill in bare areas created by the weed dying” (Illinois Extension).
• Fall applications are usually safer for the lawn and nearby plants “because of lower air temperatures and fewer ornamentals are present in susceptible stages” (Nebraska Extension).
• Which weeds: perennials. “Most annuals die off quickly in fall, but perennials do not” (Illinois). Summer annuals such as spurge and purslane “die following the first hard frost in the fall” (Nebraska), so don’t spray them now.

Species guides: dandelion clover wild violet creeping Charlie

How late is too late: frosts and hard freezes

• “Light frosts prior to and following the application typically won’t have a negative impact,” but “several hard freezes can damage plant tissue, which reduces the weed’s ability to transport herbicide to the roots” (SDSU Extension).
• “Some recommend waiting to apply until after the first frost ..., but data show that applications throughout the fall are effective” (Nebraska).
• A hard freeze is when “the surface air temperature reaches 28°F or lower for an extended period of time” (National Weather Service).
• “Daily high temperatures should remain above 60˚F for several days prior to and following the application. Even if daily high temperatures are in the 50’s, the herbicide can still be effective” (SDSU).

About this table: median across each zone’s ZIP codes of the nearest NOAA NCEI 1991–2020 Climate Normals station’s 50%-probability date (32°F = frost, 28°F = hard freeze); the range runs from the 10th to the 90th percentile of ZIP codes. Source data: data/zonefrost.json and data/zonefreeze28.json, from NOAA NCEI normals. The rule is to spray before several hard freezes (SDSU). One hard freeze is a single 28°F night, so treat this date as the time to start finishing up, not a hard cutoff. Enter your ZIP in the planner for the dates at your nearest NOAA station.

Northern lawns: by mid-October, zones 3 to 5 are at or past their typical first hard freeze, so you may be at the end of the window. Plan a spring follow-up and see the species guides. Zone 9 and warm-season lawns: use the next section, not this table (in 16.7% of zone 9 ZIP codes the nearest station reaches 28°F in fewer than half of years).

Warm-season lawns in the South (bermuda, zoysia, St. Augustine, centipede)

• Clemson’s schedule for warm-season lawns: “November – January: Postemergence: Treat winter broadleaf weeds with a postemergence herbicide on mild days.” “Wild onions and garlic are best treated during November and again during February using a three-way herbicide” (Clemson HGIC 2310).
• Clemson: “do not make applications to established warm-season lawns during the spring green-up period,” with damage risk “especially in more sensitive turfgrasses, such as centipedegrass and St Augustinegrass.”
• “The risk of injury from postemergence herbicides is greater during the green-up process than when the turfgrass is fully dormant or actively growing” (UGA Extension B978).
• To prevent winter annual weeds before they sprout, see fall pre-emergent timing.

What to use (examples only)

Examples only. Use lawn-labeled products only, used as the label directs.

• Common mixes: “a general-purpose mixture comprised of two or three of the following ... 2,4-D, MCPP, and dicamba” (Colorado State). Illinois lists the same three.
• SDSU’s best active ingredients for fall control (examples): dandelion, 2,4-D; white clover, triclopyr, clopyralid, dicamba or quinclorac; creeping Charlie (ground ivy), triclopyr or topramezone; wild violet, triclopyr. SDSU: “make sure the label says that it’s approved for use on lawns or turf.”
• Triclopyr caution (SDSU): a “Brush Killer” label means “it’s likely not approved for use on lawns or turf.” Near trees, avoid the ester form and “Choose triclopyr triethylamine salt instead.”
• Trees: “Refer to the label regarding any potential hazards when used on lawns over the root zone of trees (such as with dicamba)” (Illinois).
• Weed and feed in fall: “Granular products usually have to be applied to wet foliage in order to stick to the leaf surface and be absorbed” (Nebraska).

Weed and feed on warm-season lawns: Texas A&M AgriLife does not recommend weed and feeds “as a fall/winter turfgrass management tool” for warm-season grasses, because “Putting nitrogen down promotes growth, and a quick freeze could cause damage.” The last nitrogen application “should be no later than four to six weeks before the average date of the first frost.” By our zone medians, that’s your typical first fall frost minus 4 to 6 weeks: in zone 8 (first frost Nov 10), about Sep 29 to Oct 13. Use the frost table above or your ZIP’s date.

Spray-day checklist

• Temperature: 50 to 85°F (Colorado State; Nebraska gives the same range). Illinois: “Avoid hot days (over 85 degrees F).”
• Rain: sources differ, so follow the label. Illinois: “no rain for 24 hours after application.” Colorado State: “Do not apply if rainfall will occur within twelve hours.” Nebraska: “Most herbicides are rainfast within 4 to 8 hours.” Moist soil helps: water “at least one day prior to application or wait for rain” (SDSU).
• Mowing: “Do not mow the lawn for two days before and after” (Colorado State); Illinois says “a few days.”

If you’re also seeding this fall

• Illinois: “wait 4 mowings before treating a newly seeded lawn and wait 30 days before seeding an area treated with broadleaf herbicides.” Colorado State and Nebraska: wait until new grass “has been mowed at least three times.” Sources differ (three vs. four mowings), so check the label.
• “Delay reseeding bare area caused by weed removal until after soaking rain or irrigation” (Nebraska).
• Timing for seed: is it too late to plant grass seed?

Prevention

Mowing high “(3 to 4-inch cut height)” helps the lawn compete with weeds (Illinois).