Why Is My Grass Turning Yellow? Diagnose It by the Pattern

The answer to why is my grass turning yellow is usually visible before you buy anything: which leaves turned first, and what shape the yellow makes. When leaves alone do not settle it, spend 48 hours on a test plot. K-State calls a sprayed iron sulfate patch “the most certain diagnostic tool” and says soil tests for iron are not reliable; UF/IFAS agrees on the soil test. We also lined up every published iron sulfate rate we could find, because they run from 1 oz to 20 oz per 1,000 sq ft.

What does the yellow look like?

Find your pattern, run the check in the third column, then treat. Twenty patterns, each tied to an extension source:

Swipe the table sideways to see every column.

What you see	Likely cause	Check	What to do	Source
Whole lawn, pale and even; lower leaves yellow first	Low nitrogen	On hands and knees, compare lower and upper leaves	Feed with soluble N; nitrate shows in a few days, ammonium in 7 to 10 days. Dose arithmetic	Arizona Turf Tips; UGA B1258; Purdue AY-22
Newest leaves yellow or striped, lower leaves green; mottled across the lawn	Iron chlorosis	Spray a small plot with iron sulfate; read it at 48 hours	2 oz ferrous sulfate in 3 to 5 gal per 1,000 sq ft, about every 6 weeks	K-State; UF/IFAS LH011; NDSU H1824
Same stripes, but the iron plot did not respond	Manganese shortage	Soil pH above 7, and a failed iron test	Soluble or chelated manganese, or manganese sulfate, at the label rate	UF/IFAS LH007; Clemson
Yellow as the lawn greens up, or just after spring fertilizer; warm days, cool nights	Cold roots lagging behind top growth	Check the forecast and soil temperature	Wait: UF/IFAS says it normally fades within a few weeks. Iron is optional	UF/IFAS EP551; NDSU H1824; UF/IFAS LH009
Fall or winter fade on a warm-season lawn	Normal dormancy	Is it bermuda or zoysia after a hard frost?	Nothing. Zoysia greens up later than bluegrass or tall fescue in spring	K-State; UF/IFAS LH007
Round spots a few inches wide, often with a darker green ring	Dog urine	Seal dead grass in a plastic bag and smell for ammonia	Water the spot; train the dog to a mulch or gravel area; re-seed or re-sod dead spots	WSU; Colorado State
Spot with an abrupt edge; no ammonia smell	Fuel, oil, fertilizer or salt spill	Gasoline leaves a roughly circular dead area; hydraulic fluid leaves straight lines	On a fresh fuel spill, detergent, then an absorbent such as activated charcoal; cut out small dead areas	WSU; UGA B1258
Repeating straight stripes across the lawn	Fertilizer spreader skips or overlap	Do stripe widths match your spreader passes?	Calibrate and overlap passes correctly; water in soluble N	UGA B1258; WSU
Streaks or a pattern that follows a sprayer, days to weeks after a weed killer	Herbicide or other pesticide injury	Match the shape and date to what was sprayed	Stop, recheck the label rate, avoid overlaps. Injury can appear quickly or several weeks later	UGA B1258
Yellow and brown on high spots, stems showing after mowing	Scalping	Look for stem-like canopy on bumps	Raise the deck. Bermuda and zoysia self-heal; tall fescue may need reseeding. Mowing frequency	UGA B1258; UGA C1003
Straw-colored tips and a gray or whitish cast	Dull mower blade	Look for small threads on the cut ends	Sharpen the blade	UGA B1258
Yellow in low or soggy areas; soft, mushy soil, musty smell	Too much water, too little oxygen	Squeeze a golf-ball-size lump from a 6 to 8 in wedge; drops of water mean too much	Cut irrigation and fix drainage. Watering schedule	Missouri; AZMET; Texas A&M
Thin and off-color along foot paths and mower routes	Compaction	Press a wire flag into moist soil; under 4 in means compacted	Core aerate; move the traffic. Aeration timing	UConn; UGA B1258
Sunny edges by the driveway or sidewalk, yellow halo around dead patches	Chinch bugs (mainly St. Augustine)	Sink a bottomless can 3 in deep, keep it filled for 5 minutes, watch for floaters	Confirm the count first; insecticide only if bugs are present, per the label	Texas A&M ENTO-PU-044; UF/IFAS IN383
Patches that feel spongy and peel back like carpet	White grubs	Cut back 1 sq ft of turf and count	See our grub thresholds	Cornell IPM; UF/IFAS LH011
Irregular patches or rings up to 3 ft across, cool and wet weather, cool-season grass	Yellow patch	No distinct leaf lesions; weather 50 to 65 F	Hold back nitrogen and improve drainage. Fungus guide	NC State
Irregular yellow patches a few inches to a few feet; short, black roots	Take-all root rot	Pull a plug and wash the roots	Do not lime. See our fungus guide	UF/IFAS LH079
Yellowing and thinning on sandy soil in hot, dry spells, mainly bermuda	Nematodes	Send soil to your county extension lab	UF/IFAS covers management in ENY006; have them identified before treating	UF/IFAS LH007; UF/IFAS LH006
Whole lawn fading to straw in a dry spell; footprints stay	Drought or heat dormancy	Screwdriver is hard to push in; bluish tint first	1 in of water a week, or after 4 to 6 weeks of dormancy 1 to 1.5 in about every 4 weeks	Iowa State; AZMET; UF/IFAS LH009
Only under trees or beside buildings	Too little light	Count direct sun hours; Floratam St. Augustine does not persist under 6	Feed shade less than sun, or change the grass. Iron chlorosis is also common in shaded St. Augustine	UF/IFAS LH010; Texas A&M

1. 1Does the yellow run in straight lines or repeating stripes?

   YesSpreader skips or overlap, or sprayer streaks. Match the lines to your last application.

   NoGo to the next question

2. 2Round spots a few inches wide, with an ammonia smell when bagged?

   YesDog urine. Water it, move the dog, re-seed dead spots.

   NoGo to the next question

3. 3A spot with an abrupt edge and no ammonia smell?

   YesFuel, fertilizer or salt spill. Treat fresh fuel with detergent and an absorbent.

   NoGo to the next question

4. 4Does the turf peel back like carpet, or are the roots black and short?

   YesWhite grubs if roots are chewed; root disease if they are black. Dig 1 sq ft and wash a plug.

   NoGo to the next question

5. 5Does a squeezed lump of soil from 6 to 8 in drip water?

   YesToo much water, too little oxygen. Cut irrigation and fix drainage.

   NoGo to the next question

6. 6Dry spell, footprints stay, and a hard-to-push screwdriver?

   YesDrought or heat dormancy. Water 1 in a week, or let it sleep 4 to 6 weeks.

   NoGo to the next question

7. 7Spring, with warm days and cool nights?

   YesCold roots. Expect it to fade within a few weeks. Iron is optional.

   NoGo to the next question

8. 8Newest leaves striped or yellow, lower leaves green?

   YesIron chlorosis. Spray a test plot and read it at 48 hours.

   NoGo to the next question

9. 9Lower leaves yellow first, even color across the lawn?

   YesLow nitrogen. Feed a test plot and read it at 7 to 10 days.

   NoRun the two-plot test, then take a sample to your county extension office.

Source: Compiled from K-State, UF/IFAS, UGA, Arizona, WSU, Missouri and Iowa State extension publications, November 2026

Is it nitrogen or iron?

Whole-lawn yellow is usually one of these two, and neither replaces the other. UF/IFAS says iron does not cure nitrogen yellowing. Going the other way is worse: Arizona Extension warns that nitrogen on severely iron-chlorotic turf can produce white leaves or straw.

Clue	Low nitrogen	Low iron	Source
Which leaves first	Older, lower leaves	Youngest, top leaves; yellow starts at the tip and moves to the base	Arizona Turf Tips; UGA B1258
Leaf look	General yellowing, tip dieback	Yellow between the veins, so the leaf looks striped; nearly white in extreme cases	UGA B1258; Texas A&M
Across the lawn	Uniform; Arizona also describes 2 or 3 shades of light green in swatches	Mottled or random patches	NDSU H1824; K-State; Arizona Turf Tips
Where it shows	Most soils, since few can supply turf’s N demand without fertilizer	Soil above pH 7, high phosphorus, sandy, cold or wet, overwatered or compacted	UGA B1258; K-State
Response to product	A few days for nitrate, 7 to 10 days for ammonium	24 to 48 hours; often gone within 2 to 4 weeks	Purdue AY-22; K-State; UF/IFAS EP551
Clippings	Few clippings, thin turf if chronic	Color without extra growth: the Texas A&M plots rated 4 and 8 for color gave the same clipping weight	Arizona Turf Tips; Texas A&M

Run the two-plot test

These are published recipes from Arizona Extension, timed to K-State‘s 48-hour window. Pick a dry, mild day with no rain coming, since NDSU warns foliar iron can burn grass under heat or drought stress.

1. Iron plot, 15 by 15 ft: mix 1 teaspoon of ferrous sulfate powder in 1/2 gallon of water and spray all of it. Do not use ferrous ammonium sulfate, which contains nitrogen.
2. Leave the iron plot unmowed and unwatered for 24 hours so the leaves take it up. K-State’s minimum is 3 to 4 hours without irrigation.
3. Nitrogen plot, 10 by 10 ft, well away from the first: spread 2 handfuls of ammonium sulfate or calcium nitrate and water it in. If you prefer to weigh it, 1/4 lb of 21-0-0 on 100 sq ft is about 0.5 lb of N per 1,000 sq ft (our arithmetic). Use a product with no iron listed on the label.
4. Read the iron plot at 48 hours, or after a few days in hot weather. Read the nitrogen plot at 7 to 10 days.

Result	What it means	Next step
Iron plot greens	Iron chlorosis	Spray the whole lawn (rates below), then get a pH number from a soil test
Nitrogen plot greens	Nitrogen shortage	Feed the lawn at a measured dose, within any local fertilizer rule
Both green	Likely short of both (our reading, not a published rule)	Feed first, then spray iron between feedings, as Clemson suggests for zoysia
Neither greens, pH above 7	Possibly manganese	Soluble or chelated manganese per UF/IFAS LH007 and the product label
Neither greens, normal pH	Not a nutrient problem	Wash the roots and go back to the pattern table: excess water, compaction, disease and insect injury all restrict roots (K-State)

Iron only masks the cause. NDSU says the one way to treat an iron-deficient soil at its source is to acidify it with sulfur, and K-State caps sulfur on established turf at 5 lb per 1,000 sq ft at one time, so the rates and timing live in our guide on how to make soil acidic with sulfur. Do not lime yellow turf without a pH number.

How much iron sulfate should you use?

Start at 2 oz of ferrous sulfate in 3 to 5 gallons of water per 1,000 sq ft, about 10 oz in 15 to 25 gallons for 5,000 sq ft. On strongly alkaline soil expect that to fall short: Texas A&M‘s 1994 trial on St. Augustine at pH 8.0 rated the 2x rate disappointing and concluded alkaline soils need 2 or 3 times the low label rate. The published rates below differ by up to 20 times, so we converted each at the 20 percent iron that UF/IFAS lists for iron sulfate.

Source	Published rate	Ferrous sulfate per 1,000 sq ft	lb iron per acre	What it reports	Link
NDSU H1824, foliar	0.012 to 0.024 lb iron per 1,000 sq ft in 1 to 5 gal	1 to 1.9 oz	0.5 to 1	As often as needed; avoid heat and drought stress	NDSU H1824
Cornell	1 to 2 oz ferrous sulfate spray per 1,000 sq ft	1 to 2 oz	0.5 to 1.1	2 to 3 weeks in fast growth, months in slow growth	Cornell
UF/IFAS lawn sheets; Clemson	2 oz in 3 to 5 gal per 1,000 sq ft	2 oz	1.1	Repeat about every 6 weeks	UF/IFAS LH006; UF/IFAS LH011; Clemson
Texas A&M trial, soil pH 8.0	3 times the 2 oz low rate was the first iron sulfate rate to hold a 7 of 9 color rating	6 oz	3.3	Rated desirable through week 5; 2 oz did not get there	Texas A&M
UF/IFAS EP551, foliar	1 to 5 lb iron per acre	1.8 to 9.2 oz	1 to 5	Up to 4 weeks; above 5 lb, more leaf burn risk and possible black leaves	UF/IFAS EP551
K-State, foliar	0.25 lb iron per 1,000 sq ft	20 oz	10.9	Green in 24 to 48 hours, may last only a few weeks	K-State
NDSU H1824, granules	0.25 lb iron per 1,000 sq ft	20 oz	10.9	Green in 24 to 48 hours, about 2 weeks	NDSU H1824
UGA C1003, centipede	1 tablespoon in 3 gal per 1,000 sq ft	Volume only, not converted	Not converted	Repeat every 2 to 4 weeks	UGA C1003

1. NDSU foliar1.90
2. Cornell2
3. UF/IFAS lawn sheets2
4. Texas A&M at pH 8.06
5. UF/IFAS ceiling9.20
6. K-State foliar20
7. NDSU granules20

Source: The Green Industry Report conversion of published rates at 20 percent iron, November 2026 Rates published as lb iron are converted by us. Same numbers as the table above.

Show the numbers

	Ounces of ferrous sulfate per 1,000 sq ft
NDSU foliar	1.90
Cornell	2
UF/IFAS lawn sheets	2
Texas A&M at pH 8.0	6
UF/IFAS ceiling	9.20
K-State foliar	20
NDSU granules	20

The 20 oz figures from K-State and NDSU sit at about twice the 5 lb per acre ceiling UF/IFAS EP551 sets, and UF/IFAS reports more burn risk and black leaves past it. We cannot settle that from documents, and these programs work on different soils. The cautious reading: stay between 2 and 9 oz, try anything higher on a small patch first, and let your product label overrule all of it.

Granules are the other split. NDSU lists them, but UF/IFAS found only foliar iron sulfate gave a positive response in Florida, with as much as 95 percent of soil-applied iron unavailable within 1 hour. Iron oxide and iron sucrate gave no response in its research, so read the ingredient list. Above pH 7.2, K-State and NDSU both point to Fe-EDDHA chelate.

Iron stains. UF/IFAS warns of reddish-brown marks on sidewalks, driveways and patios that are difficult to remove, and NDSU says to rinse any contact with water at once. Sweep or rinse hardscape before the spray dries.

Iron is one of several ways to deepen color, and our page on how to make grass greener ranks it against turf colorant, quick-release nitrogen and darker cultivars by days to green and weeks it lasts.

Why is my grass turning yellow in spring?

Most often because the top is growing faster than the roots can feed it. Warm days push leaves while cool nights hold roots back, says UF/IFAS of centipede. UF/IFAS EP551 adds the part that puzzles homeowners: spring nitrogen makes it worse on bahia, centipede and St. Augustine, because it raises iron demand while roots are still limited, and cool, wet soil deepens it. These episodes normally fade within a few weeks as soil warms.

Grass	Iron trouble above pH	What spring yellow looks like	What to do	Source
St. Augustine	7.0	UF/IFAS names it among the grasses that go chlorotic after spring nitrogen. Floratam is much less prone to iron chlorosis than other cultivars; Raleigh yellows in peak summer heat	Wait a few weeks or spray foliar iron. Shaded areas need less fertilizer	UF/IFAS EP551; UF/IFAS LH010; Texas A&M
Centipede	6.0 to 6.5	Naturally pale yellow-green and worst in early spring, so a light cast is normal	About 1 lb N per 1,000 sq ft a year in 3 or 4 light feedings (2 lb on sandy, high-rain soils). Spray iron, not more nitrogen	UF/IFAS LH009; UGA C1003
Zoysia	7.0	Greens up later than bluegrass and tall fescue. Early-spring yellow can be iron or manganese while soil lags air temperature	Do not push it with early nitrogen: UF/IFAS says early-spring and late-fall N significantly raises large patch risk	UF/IFAS LH011; Clemson; K-State
Bahia	7.0	Named with St. Augustine and centipede for chlorosis after spring nitrogen	Ferrous sulfate spray every 6 weeks; avoid oxide forms of iron	UF/IFAS LH006; UF/IFAS EP551
Bermuda	7.0	Poor shade tolerance and no green color in cold weather; nematodes also yellow it on sand	Manganese or foliar iron on high-pH soil; granular iron only as a chelate	UF/IFAS LH007
Kentucky bluegrass	Moderate to high susceptibility (no number given)	Can look chlorotic right after spring green-up in North Dakota until soil reaches 50 to 55 F	NDSU: no iron needed at that point	NDSU H1824; K-State
Tall fescue	Moderate to low susceptibility (no number given)	Yellow patch shows in cool wet weather at 50 to 65 F	Keep spring N at or under 0.25 lb per 1,000 sq ft while it is active; scalped areas may need reseeding	K-State; NC State; UGA B1258

Yellow that is still there once nights stay warm is no longer a cold-soil problem. UGA says to sample for pH and fertility if centipede yellows as it greens up, and UF/IFAS LH079 notes take-all can be active on roots for 2 to 3 weeks before leaves show it. Wash a plug: white roots point back to nutrition, and black, rotted roots point to our lawn fungus guide.

Spots, rings and stripes: what landed on the lawn?

Seal dead grass from a round spot in a plastic bag and smell it: WSU says urine releases ammonia, while fertilizer or salt spills do not. Colorado State calls water the only thing that neutralizes urine and says gypsum and baking soda are salts that may compound the problem. Urine-acidifying supplements fail too, since spots are not caused by alkaline urine. Large dogs and dogs that squat are the usual sources.

Straight lines are nearly always man-made. UGA B1258 ties green-shaded stripes to spreader passes that did not overlap, and broad to narrow streaks to pesticide overlap. Urea on wet turf or in high temperatures can burn leaves, so water it in. Turns and stops are where WSU says excess fertilizer gets dropped, and quick-release products not watered in are a common cause.

Why is my grass yellow even though I water it?

Because water can be the cause. Texas A&M says plants need well-aerated soil to take up iron, and that excess irrigation and compaction both cut uptake. UGA B1258 goes further: saturated soil displaces oxygen and roots can die. Missouri gives the check: cut a wedge 6 to 8 in deep and squeeze a golf-ball-size lump. Drops of water mean too much or too often; soil that holds together and looks moist is about right.

If soil is dry and hard but the sprinklers run, you have a coverage or infiltration problem. AZMET lists a hard-to-push screwdriver and a bluish-gray tint as underwatering signs. On St. Augustine, check before adding water: Texas A&M says chinch bug damage looks like drought and starts at about 20 to 25 bugs per sq ft, often beside driveways and sidewalks. UF/IFAS floats them out with a bottomless can sunk 3 in and kept full for 5 minutes.

Is it dormant, shaded or just cut too short?

Grass moving from green to blue-gray to yellow to brown is the normal drought sequence, per UF/IFAS. Iowa State says Kentucky bluegrass and other cool-season lawns can stay dormant 4 to 6 weeks without significant damage; past that, apply 1 to 1.5 in of water about every 4 weeks to keep crowns alive, which will not green it up. Traffic shortens survival, per Wisconsin, so stay off.

Under trees, count sun. UF/IFAS says Floratam St. Augustine does not persist under 6 hours of daily sun, and bermuda has poor shade tolerance, so yellowing there is a site problem that fertilizer will not solve. After a low cut, UGA B1258 expects brown and yellow turf with stems showing; bermuda and zoysia regrow on their own, and tall fescue may need seed.

Grass selection, mowing and feeding beyond this diagnosis are in our turf and trees hub.

This page is general information. Fertilizer rules vary by state and county, and for any pesticide the label is the law. Follow the label on the product in your hand, and confirm a local diagnosis with your county extension office.