Prep first
Before you start
- Treat it as soon as you can; the longer it sits, the harder it is to clean.
- Keep heat away. Hot water, an iron or a dryer can set protein stains.
- Test any cleaner on a hidden spot first.
Fresh grass on a deck is the easiest to lift, and every day it sits, the green gets harder to remove from the boards. Weathered or gray wood, and decks with old stain or sealer, need a different plan than clean, bare wood. Keep the water gentle and save stronger options for stains that won't lift.
Pick the mildest step first, since pressure-treated pine and weathered gray wood can react differently to stronger products. Brush with the grain so the cleaner doesn't leave streaks. If a dark mark survives repeated gentle rounds, stop and reassess instead of scrubbing harder.
Before you start
What decks & wood fences can take
Safe to use2
- Water
- Oxygen bleach
Use with care5
- Soaking
- Chlorine bleach
- Solvents (alcohol, spot removers)
- Acids (vinegar, lemon)
- Scrubbing and abrasives
5 items
What you'll need
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- Liquid mild soapMakes the suds for the stain. (opens Amazon)
- Lukewarm waterMixes the suds to a good volume.
- Stiff synthetic-bristle brushScrubs along the grain. (opens Amazon)
- SpongeApplies the suds and does the final wipe. (opens Amazon)
- Garden hoseRinses the suds out on low-pressure spray.
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6 steps
Step by step
Step 1 of 6
Brush off the loose clippings
Sweep or brush off the loose clippings and blades before any water touches the deck. Clearing them first lets the suds reach the stain itself.
Step 2 of 6
Mix mild soap into lukewarm water
Pour lukewarm water into a bucket and add a mild liquid soap. Swish it until you have a great volume of suds, then keep the bucket close for the sponge.
Careful. Bar soap or soap flakes make tannin-type stains harder to remove, so stick with liquid.
Step 3 of 6
Apply the suds to the stain
Dip a sponge in the suds and apply them to the stain, covering the whole mark. Keep the area wet while you work.
Tip. Work one section at a time so you can rinse it before the suds dry.
Careful. Don't let cleaners or soap dry on the deck.
Step 4 of 6
Scrub along the grain
Scrub the stain with a stiff synthetic-bristle brush, working along the grain rather than across it. Stop once the green lifts instead of pushing harder on one spot.
Step 5 of 6
Rinse with low-pressure hose spray
Rinse the area with a garden hose on low-pressure spray until no suds are left on the wood. Move the spray steadily so the water doesn't pool in one spot.
Step 6 of 6
Wipe the wood dry
Go over the area once more with a sponge dampened with clear water, then wipe it dry. Let the deck dry fully before you judge the result.
If you'd rather buy than mix
Best products for grass on decks & wood fences
Pick a deck cleaner labeled for wood for set-in spots, and a liquid mild soap for the suds.
OxiClean Versatile Stain Remover Powder
How we picked these: each product is made for this type of stain, its maker doesn't warn against using it on decks & wood fences, and its directions fit the steps above.
Finished the steps? How does it look?
Nice work. Let it dry completely and check it again in good light. Here is what done looks like:
How to tell it's really gone →A faint mark usually needs one more round, not a stronger product.
Heavy buildup usually takes more than one round.
Heavy or long-standing buildup →When to call a professional →How to tell it's working
You'll know it's working when the green starts to lift and the suds turn green as they pick it up. If the wood still looks green once it's dry, move on to the set-in options.
What changes for yours
Adjust for your decks & wood fences
Pressure-treated pine
Pressure-treated pine takes the same suds and hose-rinse steps as any wood deck. The one change is what you reach for when the suds fail: oxygen bleach or 3% hydrogen peroxide, never chlorine.
Let each board dry fully between passes so you can see how much green is left. Only then decide whether the set-in options are worth it.
Old CCA-treated deck
Old decks treated with CCA need extra care around people. Wetting the wood raises surface arsenic, and bleach releases chromate, so keep children and pets off wet wood and leave bleach out altogether.
Let each area dry before you move to the next one. Keep the suds and hose rinse as the only cleaning steps.
Weathered gray wood
Grayed wood has lost much of its natural color, and the suds alone won't bring it back. Commercial deck cleaners, brighteners or restorers remove the mildew and dirt so the wood's own color can show. If all the natural color has leached out, the wood stays silver when dry, and those fibers should be left in place.
Test one board first and let it dry before judging the color.
Old stain or sealer
Old stain or sealer has to come off before you can judge the grass stain. Remove it with a stain and sealer remover, then neutralize the wood with a brightener. Lightly sand the boards once they're dry, not while they're wet.
Treat the grass only after the finish is gone, so you can see the stain clearly.
Concrete or stone deck
A concrete or stone deck isn't wood, so the soap steps don't apply. Make a solution of washing soda or detergent in water, with no soap added, and scrub gently with a cloth or soft-bristled brush. Rinse thoroughly with clear water and let the surface dry.
For concrete or brick stains beyond the deck, the Concrete, Brick & Driveways guide covers the full routine.
Heavy or long-standing buildup
Old grass is harder than fresh grass, so expect to repeat the suds and scrub along the grain more than once. Work one section at a time, rinsing each one before you move on.
If the green has dried into the boards, apply a deck cleaner and keep it wet on the wood about 15 minutes, misting with a hose if it starts to dry. Use it only on set-in spots, not the whole deck.
If it's still there, oxygen bleach (sodium percarbonate) or 3% hydrogen peroxide is the next step for organic stains like grass. Rinse out whichever you use with clear water before the wood dries. Be realistic: a stain that has been set for a long time may lighten more than it disappears.
Vinegar, baking soda, peroxide and more
Do home remedies work on grass on decks & wood fences?
Plenty of household tips for grass come from fabric or stone, so most don't belong on a deck. Here's how each one fits a wood deck and where it lands in the steps.
Helps2Skip4
What makes it worse
Mistakes to avoid
Don't use chlorine bleach on pressure-treated decks
Bleach breaks down the wood, corrodes metal fasteners, harms plants, and doesn't kill mildew spores. Never mix it with ammonia either, since that forms a toxic gas.
Don't aim a tornado tip at the deck
Narrow-stream and rotating tornado tips on a pressure washer can damage decks. The low-pressure hose spray in the rinse is all you need.
Don't use steel wool or wire brushes
Leftover iron from steel wool or wire brushes reacts with the wood and stains it. A stiff synthetic-bristle brush does the scrubbing without that risk.
Don't power wash or scrub soft wood hard
Caustic cleaners and power washing remove the surface of soft woods like western redcedar. Keep the brushing light and let the suds do the work.
When to call a professional
No firm line is given for when to call a pro. Pressure washing is the main risk, since a deck can be damaged in the wrong hands, so a pro is worth it for a large or heavy job. If the lumber is old and CCA-treated, replacing it is safer than cutting or burning it, because sawdust and smoke carry arsenic.
Questions
Will grass stain a deck permanently?
It doesn't have to. Grass stains get harder to clean the longer they sit, so brush off the clippings and start the suds as soon as you can.
Do I need to sand the deck to remove a grass stain?
Usually not. Sanding is a last resort, done lightly and only once the boards are dry after an old finish has been removed. Try the suds and the deck cleaner first.
How long should a deck cleaner stay on the wood?
About 15 minutes, misting with a hose if it starts to dry out. Use it only after the suds have failed on a set-in spot.
What if the stain is still there after one wash?
Repeat the suds on that spot, then move to the set-in options. Be realistic: a long-set stain may lighten more than it vanishes.
Can I use this method on composite decking?
This method is written for wood. If your deck is composite or you can't tell what it's made of, test the suds on a hidden board first and follow the maker's care instructions.
Can I use oxygen bleach on a wood deck?
Yes, for organic stains like grass it's a set-in option the wood can take. Use it after the suds, and rinse it out well with clear water before the wood dries.
Grass on other materials
Other stains on decks & wood fences
Start from the bigger picture
How we know this
Every method, amount and warning here comes from university extension services, industry bodies and product makers. We read them, check every step for unsafe combinations and changed amounts, and write it up so you can follow it.