What Kills Thistles but Not Grass: Labels by Species

We read 11 store-shelf EPA labels and sorted them by thistle, because no bottle covers every species on every grass: Scotts 538-333 names Canada and bull but not musk, and Roundup For Lawns Southern 2217-1010 names bull but not Canada. Two actives that keep coming up in forum threads, clopyralid and aminopyralid, are barred from home lawns by their own labels. Download the matrix, doses and state lists.

General information, not pesticide or legal advice, and no product endorsement. The label is the law: the label on your container overrides this page.

Which thistle is in your lawn?

Check the stem first. Penn State separates them this way: Canada thistle has a smooth stem between the leaves and flower heads under 1 inch, while the biennials carry spiny wings along the stem. Canada thistle is the hard one, since one plant can colonize a circle 3 to 6 feet wide in 1 or 2 years (CSU). Bull and musk thistle spread only by seed and die after seeding, which makes them “much easier to control” (Iowa State).

Thistle	Life cycle	Fastest tell	Flower head	Roots	Source
Canada thistle (Cirsium arvense)	Perennial	Stem smooth between the leaves, no spiny wings; grows in patches	0.5 to 1 in tall, in clusters; bracts without sharp spines	Roots 15 ft or more sideways, 6 to 15 ft down	CSU; Iowa State; Penn State
Bull thistle (Cirsium vulgare)	Biennial	Hairy leaves, each narrow tooth tipped with a sharp spine; wings on upper stem	2 to 3 in tall, gumdrop shape; long, stiff spine on each bract	Taproot, no spreading roots	Iowa State
Musk thistle (Carduus nutans)	Biennial	Silvery or white leaf margins; spiny wings; heads droop	1 to 2 in tall, 2 to 3 in wide; broad, sharp bracts	Large, corky taproot, hollow near the crown	Iowa State; CSU
Annual sowthistle (Sonchus oleraceus)	Annual	Only very small spines on leaf edges; white sap when broken	Yellow, 0.75 in or smaller	Shallow taproot	Penn State; Cornell
Perennial sowthistle (Sonchus arvensis)	Perennial	Prickly teeth pointing toward the leaf base; white sap	Bright yellow, dandelion-like, 1 to 2 in wide	Up to 10 ft deep and 9 ft sideways	Cornell

1. 1Do broken stems or leaves ooze white sap, with yellow dandelion-like flowers?

   YesSowthistle. Annual type: hand-pull the shallow taproot. Perennial type (flower heads 1 to 2 in, deep roots): check that your label covers it, and repeat as with Canada thistle.

   NoGo to the next question

2. 2Is the stem smooth with no spiny wings, in a patch, with flower heads under 1 inch?

   YesCanada thistle. Spray a label that names it at flower bud and again in fall, for several years.

   NoGo to the next question

3. 3Are spiny wings on the stem, and is it still a flat rosette?

   YesBull or musk thistle. Spray in fall or early spring, or sever the root below the crown.

   NoGo to the next question

4. 4Are spiny wings on the stem, and has it bolted into a flower stalk?

   YesBull or musk thistle past the spray window. Cut below the crown with a spade before seed forms; musk starts 45 to 55 days after bolting.

   NoNot one of these. Take a photo to your county extension office before you buy; some native thistles are not lawn invaders.

Source: Penn State, Iowa State, CSU, Cornell

Which lawn labels name which thistle?

This table is the page’s core: each label’s own weed list, checked against 4 thistle groups, with its grass exclusions and yearly cap. “Named” means the species appears on the EPA master label. The Ortho triclopyr and Scotts master labels both warn that some or all listed weeds will appear on the package, so the container in your hand can list fewer. Rates are per 1,000 sq ft of lawn.

Product (EPA Reg. No.)	Actives	Canada	Bull	Musk	Sowthistle	Do not use on	Yearly limit	Rate per 1,000 sq ft
Ortho WeedClear / Weed B Gon Lawn Weed Killer concentrate (239-2744)	2,4-D, MCPP-p, dicamba	Named	Named	Named	Named (common)	Bentgrass, carpetgrass, dichondra, lippia, seashore paspalum, Floratam	2 a year, 30 days apart	4 fl oz cool-season; 2 fl oz warm-season; 1 fl oz centipede or St. Augustine on the pressure-sprayer chart
Spectracide Weed Stop For Lawns Concentrate2 (9688-342-8845)	2,4-D, MCPP-p, dicamba, sulfentrazone	Named	Named	Named	Named (annual, spiny)	Floratam, Bitterblue, carpetgrass, dichondra	2 a year, 2 weeks apart	4 fl oz cool-season and zoysia; 2 fl oz bahia, bermuda, centipede; 1.5 fl oz St. Augustine
Gordon’s Trimec Lawn Weed Killer (2217-539-33955)	2,4-D, MCPP-p, dicamba	Named	Named	Named	Named (annual, spiny)	Carpetgrass, dichondra, Floratam in Florida	2 a year, 30 days apart	4 fl oz cool-season, bahia, bermuda, zoysia; 2 fl oz centipede or St. Augustine
BioAdvanced Southern Weed Killer for Lawns (92564-4)	2,4-D, MCPP-p, dicamba	Named	Named	Named	Named (spiny and unspecified)	Carpetgrass, dichondra, Floratam	2 a year, 30 days apart	4 fl oz northern grasses, bermuda, buffalo, zoysia; 2 fl oz bahia, centipede, St. Augustine
Preen Lawn Weed Control granules (961-418)	2,4-D, MCPP-p, dicamba	Named	Named	Named	Named (spiny and unspecified)	Carpetgrass, dichondra, St. Augustine	2 a year, 30 days apart	2 lb granules
Scotts Turf Builder Weed & Feed5 (538-333)	2,4-D, dicamba, fertilizer	Named	Named	No	Named (unspecified)	Creeping bentgrass, St. Augustine, dichondra, carpetgrass, lippia	2 a year	2.82 lb granules, on wet grass
Roundup For Lawns1, Northern (no glyphosate) (2217-917-71995)	MCPA, quinclorac, dicamba, sulfentrazone	Named	Named	Named	Named (annual, spiny)	Bentgrass, St. Augustine, bahia, centipede, carpetgrass, dichondra	2 spot sprays a year, 21 days apart	Ready to use; at most 1 gal
Roundup For Lawns Southern concentrate (no glyphosate) (2217-1010-71995)	2,4-D, dicamba, penoxsulam, sulfentrazone	Only as “Thistle”	Named	Only as “Thistle”	No	Bentgrass, carpetgrass, dichondra (Floratam allowed)	2 broadcasts a season, 30 days apart	5.2 to 8.6 fl oz St. Augustine; 7.2 to 10.6 fl oz bluegrass
Ortho Weed B Gon Chickweed, Clover & Oxalis Killer (239-2491)	Triclopyr	Lawn sublabel: “Thistle”; brush sublabel: Canada	Only as “Thistle”	Only as “Thistle”	No	Bahia, bermuda, centipede, kikuyu, St. Augustine	Repeat after 2 to 3 weeks; 5.4 fl oz per 100 sq ft a year	1 fl oz in 1 gal per 200 sq ft (5 fl oz per 1,000)
Southern Ag 2,4-D Amine (signal word Danger) (48273-4-829)	2,4-D amine	Warned: “usually require repeated applications”	Named	Named	Named (annual)	Injury warning: bentgrass, St. Augustine, carpetgrass, centipede, dichondra, clovers	2 a year	3 pints per acre (6.5 tsp)
Sunday Dandelion Doom (67702-27-93737)	Iron HEDTA	Named, not in California	Named	No	No	Bentgrass, dichondra	Repeat in 3 to 4 weeks	Ready to use; spray weeds thoroughly

For Canada thistle on bluegrass, fescue or ryegrass, the 2,4-D, MCPP and dicamba concentrates from Ortho and Gordon’s name it at 4 fl oz per 1,000 sq ft, and Iowa State lists those actives as effective. On St. Augustine the rate falls to 1 to 2 fl oz, and Floratam is off most labels. Of these 11, only Roundup For Lawns Southern names Floratam as allowed, and it does not name Canada thistle. No label here names perennial sowthistle; 4 list plain “sowthistle”, so ask the registrant whether that covers it.

Triclopyr suits cool-season lawns only: the Ortho label excludes bahia, bermuda, centipede, kikuyu and St. Augustine, but it permits seeding 1 week after spraying, against 3 to 4 weeks for the three-way. SDSU warns that “Brush Killer” bottles are likely not approved for lawns and that ester triclopyr is the more volatile form near trees. Our weed killer comparison covers the wider product set. Professional labels naming Canada thistle include Turflon Ester Ultra (62719-566), Tenacity (100-1267) and Celsius WG (432-1507).

Why not clopyralid or aminopyralid?

Because the labels forbid it on home lawns, even though they are the thistle specialists. SDSU lists clopyralid as the best active for Canada thistle, then notes Lontrel cannot go on residential turf. EPA wrote in its December 2020 interim decision that residential lawn uses of clopyralid have been canceled. A license does not change this on these labels: the Confront restriction is on the site, not the person.

One conflict to settle: Penn State’s home-garden page calls clopyralid and aminopyralid “often used for lawn settings,” while Penn State’s turf fact sheet says certain clopyralid products should not go on residential turf and NativeKlean should not go on home lawns. We side with the labels below.

Product or active	Thistle record	On your home lawn?	Source
Confront, triclopyr + clopyralid (62719-92)	Label lists Canada and musk thistle	No: “Do not use on residential turf.” Also bars clippings from compost and mulch	Label
Lontrel, clopyralid	SDSU: better thistle control than common lawn blends	No: cannot be applied to residential turfgrass	SDSU
Milestone, aminopyralid (62719-519)	88 to 93% Canada thistle control in western pasture and range work, per Landschoot 2023	No: “Do not apply this product to lawns, turf, ornamental plantings”	Label; GCM
NativeKlean, aminopyralid + 2,4-D	Fast burndown in Penn State trials	No: native or natural areas that are not regularly mowed	Penn State; GCM
Glyphosate (standard Roundup)	Bud to flower spot treatment works on thistle	Only if you accept dead grass: it is non-selective	Iowa State
Vinegar	Top growth only; roots regrow	Not advised: it can kill the surrounding turf	Ask Extension

You may give up less than that sounds. In Penn State trials on Chewings fescue rough in 2021 and 2022, AquaSweep (triclopyr + 2,4-D) produced injury comparable to Lontrel and Confront in both years. The limits matter: one spray per season, foliar injury ratings to 40 and 55 days, no root counts, a golf rough rather than a lawn, and AquaSweep itself is not labeled for Canada thistle.

Why a lawn spray takes years on Canada thistle

Lawn labels deliver less 2,4-D than the pasture programs behind most thistle advice. At the rates below, the common concentrates apply 0.74 to 0.84 lb acid equivalent per acre, about 37 to 42 percent of the 2 lb per acre in CSU‘s pasture program. That is one plausible reason SDSU expects “several applications over multiple years” from store blends. It is our inference, not a trial result, and raising the dose is not the fix: the Ortho label says exceeding directed rates may damage turf.

1. Roundup Southern0.40
2. Gordon's0.74
3. Spectracide0.74
4. Ortho0.84
5. Preen1.20
6. Southern Ag1.43
7. Scotts W&F51.50
8. CSU pasture2
9. Iowa State pasture2

Source: EPA labels; CSU and Iowa State Extension One application at the label rate on a cool-season lawn. Pasture bars are not lawn directions. CSU bar assumes a 4 lb per gallon product.

Show the numbers

	lb acid equivalent per acre
Roundup Southern	0.40
Gordon's	0.74
Spectracide	0.74
Ortho	0.84
Preen	1.20
Southern Ag	1.43
Scotts W&F5	1.50
CSU pasture	2
Iowa State pasture	2

Program	2,4-D, lb acid equivalent per acre, one application	How we got it
Roundup For Lawns Southern, 10.6 fl oz (2217-1010)	0.40	As stated on the label
Gordon’s Trimec, 4 fl oz (2217-539)	0.74	As stated on the label
Spectracide Concentrate2, 4 fl oz (9688-342)	0.74	As stated on the label
Ortho concentrate, 4 fl oz (239-2744)	0.84	As stated on the label
Preen granules, 2 lb (961-418)	1.20	As stated on the label
Southern Ag Amine, 3 pints per acre (48273-4)	1.43	3 pints x 3.8 lb acid equivalent per gallon, our arithmetic
Scotts Weed & Feed5 (538-333)	1.50	As stated on the label
CSU pasture program, Canada thistle, 2 qt per acre	2.00	Assumes the common 4 lb per gallon product
Iowa State pasture program, biennial thistles, top of 1 to 2 qt	2.00	Iowa State states 4 lb acid equivalent per gallon

When to spray each thistle

Thistle	Spray window	Too late or wrong	Source
Canada	Fall while leaves are green, even after first frost; and early summer as flower buds form (late May to mid-June in New Jersey)	Spring-only spraying: new shoots keep coming from root buds, so one spring application rarely lasts the season	Iowa State; Rutgers; GCM
Bull, musk	Rosettes in fall, even after several frosts, or early spring before bolting	After bolting, when tolerance rises sharply. Cut instead: musk starts making seed 45 to 55 days after bolting	Iowa State; CSU
Annual sowthistle	Hand-pull; the shallow taproot comes out easily. Seedlings form a low rosette that often goes unnoticed	Waiting until late summer to October, when yellow flowers set wind-borne seed	Penn State
Perennial sowthistle	We found no lawn-specific timing study. Spray while actively growing, per label, if your label covers it	No spray window to miss, but non-chemical work is slow: hay mown 3 times a season for 2 years substantially cut density	Cornell

Most three-way labels allow only 2 applications a year, at least 30 days apart (Ortho, Gordon’s, BioAdvanced), so spend them on the 2 Canada thistle windows: bud stage, then fall. Ask Extension told a Denver homeowner to plan on 2, more likely 3, applications. Spray day runs like this:

1. Match the grass and thistle to your container’s label. Mixed lawn: BioAdvanced says use the lowest rate.
2. Check the forecast: under 90°F on most labels, 85°F on St. Augustine with Roundup For Lawns Southern and on bermuda with Roundup For Lawns1. Montana State goes lower, at 80°F, to limit dicamba vapor drift. For fall sprays, SDSU wants highs above 60°F for several days around the application.
3. Do not mow for 2 days before or after (Ortho). Skip it above 10 mph wind (Ortho triclopyr).
4. Mix fresh, use a coarse nozzle, and wet the thistle without runoff. Keep it off exposed tree roots and ornamentals.
5. Keep it dry: 24 hours on Ortho, 6 hours on Ortho triclopyr, 3 hours on Roundup For Lawns1.
6. Wait 30 days. Ortho says repeat if tough weeds are not dead by then; dead Canada thistle stems can stay rigid and upright for much of the summer (Penn State).
7. Seed bare patches only after the label wait, then follow our overseeding steps. A dense canopy starves thistle seedlings of light (Penn State).

How much to mix for a thistle patch

The label rate is small per square foot: 4 fl oz per 1,000 sq ft is 0.024 teaspoons per sq ft. Measure the patch, then use the rate your label gives for your grass. Gordon’s defines a spot treatment as no more than 1,000 sq ft per acre, and the 4 fl oz per 1,000 sq ft ceiling still applies.

Patch area (sq ft)BasisLabel rate for one applicationLabel and grassOrtho 239-2744 or Gordon's 2217-539: bluegrass, fescue, ryegrass (4 fl oz per 1,000)Spectracide 9688-342: cool-season, zoysia (4 fl oz)BioAdvanced 92564-4: northern, bermuda, buffalo, zoysia (4 fl oz)Gordon's 2217-539: bahia, bermuda, zoysia (4 fl oz)Ortho 239-2744: bahia, common bermuda, zoysia (2 fl oz)Spectracide 9688-342: bahia, bermuda, centipede (2 fl oz)Gordon's 2217-539: centipede, St. Augustine, not Floratam (2 fl oz)BioAdvanced 92564-4: bahia, centipede, St. Augustine, not Floratam (2 fl oz)Spectracide 9688-342: St. Augustine, not Floratam or Bitterblue (1.5 fl oz)Ortho 239-2744 pressure sprayer: centipede, St. Augustine, not Floratam (1 fl oz)Ortho triclopyr 239-2491: cool-season only (5 fl oz)

Concentrate (fl oz)

0.40

Concentrate (teaspoons)

2.4

Concentrate (tablespoons)

0.8

Default: 100 sq ft at 4 fl oz per 1,000 sq ft needs 0.40 fl oz, or 2.4 teaspoons. Label rates, read November 2026. Your container's label overrides this tool; water volume also differs by label.

Patch	Concentrate at 4 fl oz per 1,000 sq ft	Concentrate at 2 fl oz per 1,000 sq ft	Spray volume at Ortho’s 1 gal per 1,000 sq ft
25 sq ft	0.1 fl oz (0.6 tsp)	0.05 fl oz (0.3 tsp)	3.2 fl oz
100 sq ft	0.4 fl oz (2.4 tsp)	0.2 fl oz (1.2 tsp)	12.8 fl oz
250 sq ft	1 fl oz (2 Tbsp)	0.5 fl oz (1 Tbsp)	1 qt
1,000 sq ft	4 fl oz (8 Tbsp)	2 fl oz (4 Tbsp)	1 gal

Do mowing, pulling or digging work?

On biennials, yes, and fast. On established Canada thistle, only as a multi-year campaign, because root pieces 0.25 inch long can restart a plant and shoots return about 15 days after disturbance (CSU). Sources disagree on the cutting interval, so the table gives each one.

Method	Thistle	Schedule or threshold	Result reported	Source
Hand-pull	Canada seedlings	Before 3 leaves, on a regular schedule, spring through fall. Seedlings turn perennial 7 to 8 weeks after germination	Drastic reduction over 2 years	Rutgers; CSU
Pull or dig	Canada, a few plants	Every 2 to 3 weeks, or when new stems show; bag the plants	Useful only for small numbers	Montana State
Cut, do not pull	Canada, home garden	Every 2 to 3 weeks with shears or a trimmer. Pulling can stimulate root buds	2, 3 or more years	Penn State
Mow or trim	Canada, established	Every 7 to 10 days, late spring through bloom	Stops seed; lowers root reserves	Rutgers
Mow	Canada, established	6 or more times a season for several years	May control it; fewer mowings only contain it	Iowa State
Mow plus spray	Canada, high water table	Start at 12 to 15 in tall, monthly, 3 times, then Curtail in October (pasture, not lawns), 2 years running	Better than Curtail alone	CSU
Shovel or hoe	Bull, musk	Sever the root below the crown, once	Removes the plant	Iowa State; CSU
Mow	Bolted bull, musk	At least 2 mowings in summer, since crown buds resprout	Stops seed	Iowa State

Routine lawn mowing helps young plants more than old ones: Iowa State says frequent mowing can exhaust young Canada thistle and prevent bloom, while established stands are often unfazed. Our mowing frequency page covers intervals. Buried seed can last 20 to 22 years (Rutgers; CSU), though most near the surface die within a few years, so scout every spring.

Does your state make you control thistles?

In many states, yes, and a thistle in your lawn can be a legal matter as well as a nuisance. Maryland requires landowners to eradicate or control listed thistles, Minnesota says Canada and plumeless thistle must be controlled on all lands, and Illinois lets counties do the work and bill the owner. These 11 are a sample from states whose official or extension lists loaded for us, not a national survey; ask your county weed office what applies locally.

State	Thistles on the state list	Rule or duty as written	Source
Iowa	Primary noxious: perennial sowthistle, Canada, bull and every other Cirsium and Carduus thistle	Iowa Code 317.1A	Source
Illinois	Canada, musk, perennial sowthistle	505 ILCS 100; counties may manage infestations and bill the landowner	Source
Pennsylvania	Canada, musk, bull	7 Pa. Code 110.1	Source
Ohio	Canada, musk, perennial sowthistle	Ohio Adm. Code 901:5-37-01; management required on public and private land	Source
Minnesota	Canada, plumeless (Prohibited Control)	Must be controlled on all lands in the state	Source
Nebraska	Canada, musk, plumeless	Nebraska Department of Agriculture state list	Source
Colorado	List B: bull, Canada, musk, plumeless, Scotch. List C: perennial sowthistle	List B must be managed to stop spread	Source
Kansas	Category B: Canada. Category C: musk	K.A.R. 4-8-44	Source
Maryland	Bull, Canada, musk, plumeless	Landowners must eradicate or control; mowing, cultivating or an approved herbicide count	Source
Washington	Class C: bull, Canada, perennial sowthistle	WAC 16-750-015	Source
Oregon	List B: bull, Canada, musk, Scotch, Italian, milk, slender-flowered. List A: plumeless	Oregon Department of Agriculture list	Source

Paying someone to spray changes the paperwork, not the chemistry: at least 49 of 51 jurisdictions require a commercial credential for store-bought weed killer applied for pay. Ask any bidder which EPA Reg. No. they plan to use, and refuse Confront or Milestone on a home lawn.