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Autumn lawn feed moss killer

Updated: October 2026

The lawn has more moss than grass after a wet August, and the bag you picked up says autumn lawn feed moss killer as if those were the same job. They are not. Some packs in the [autumn lawn fertiliser comparison](/hub/fertiliser-soil-and-bark-mulch/autumn-lawn-fertiliser) blacken moss with iron. The liquids do not. This page is that decision: whether you want the moss gone, what will actually turn it black, and when it will come back. Spreader steps stay on the [how to apply](/hub/fertiliser-soil-and-bark-mulch/autumn-lawn-fertiliser/sub/autumn-lawn-fertiliser-how-to-apply) page. Peter F. checked the listings in October 2026. This is not a lawn trial.

The lawn has more moss than grass after a wet August, and the bag you picked up says autumn lawn feed moss killer as if those were the same job. They are not.

Our top picks

GreenCare GreenCare Autumn Lawn Feed

Best overall

GreenCare GreenCare Autumn Lawn Feed
5.7/10about £12.95
View offer
Miracle-Gro Miracle-Gro EverGreen Autumn Lawn Care 12.6 kg

Rank 2

Miracle-Gro Miracle-Gro EverGreen Autumn Lawn Care 12.6 kg
9.2/10about £24.00
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Miracle-Gro Miracle-Gro Autumn Lawn Care 80 m²

Preis-Tipp

Miracle-Gro Miracle-Gro Autumn Lawn Care 80 m²
8.9/10about £12.48
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On this page
  1. 1.Moss is not always the enemy
  2. 2.What in the bag actually kills moss
  3. 3.Black, then rake
  4. 4.When another bag will not help

Moss is not always the enemy

The RHS treats moss as a symptom as often as a foe. Shade, scalping, compaction, wet soil and acid conditions all favour it. A little moss in a dry summer lawn is not a reason to buy iron. You can rake the worst of it, raise the mower, and leave the feed on the shelf. Chemical treatment fails if the shade stays. If you do want it gone, the order matters. Westland's moss advice is to treat with an iron-sulphate moss killer before you scarify, because scarifying first spreads spores. Moss turns black, then brown. They say you normally rake after about 14 days.

What in the bag actually kills moss

Iron sulphate is the moss ingredient on the granular Miracle-Gro listings in this set. The bullets that state it say moss is killed within seven days and should be raked after two weeks. That claim sits on the EverGreen 12.6 kg bag, the 80 m² boxes, and the 4-in-1 autumn packs that mention iron or moss control. Where a listing only says moss in a coverage field and names iron sulphate, the moss claim is there and the NPK may still be missing. The buying guide is the place to check the 6-5-10 figure. The GreenCare liquids do not make that claim. They are cold-pressed seaweed, 5 ml per litre, with no NPK printed. A seaweed feed will not blacken moss. Some moss killers carry a MAPP number you can check on the HSE garden pesticides database. Ferromex, MAPP 16895, is an example outside this set. Read the pack you bought, and do not add extra.
GreenCare GreenCare Autumn Lawn Feed

Testsieger

GreenCare GreenCare Autumn Lawn Feed
5.7/10about £12.95
View offer

Black, then rake

On the Miracle-Gro bullets, blackening is expected within about seven days, and raking is about two weeks later. Westland describes the same colour change, black then brown, and a rake at about 14 days. The lawn looking dark is not, by itself, a failed feed. Scorch is the other dark lawn. On the 12.6 kg bag, reviewers describe a killed patch where a wheeled spreader dumped a heap on a turn. On the £12.29 4-in-1 box, five reviews include a lawn burnt when the reviewer says they followed the instructions. Miracle-Gro's own cap is 35 g per square metre and two applications a year. Moss that blackens, then lifts with a rake, leaving grass underneath, is the treatment the bullets describe. Grass that is bald, with granules still sitting in a stripe, is a heap. Sweep spillages off paving. Do not wash iron into a drain.

When another bag will not help

If the moss is under a fence, a conifer or a north wall, iron buys you a black fortnight and then the moss returns. The RHS shade guidance is that moss returns if the shade remains. Compaction and a mower set too low do the same job as shade. A hollow that holds water all winter needs drainage, not iron sulphate. In the Amazon reviews of the large bag, people also say moss can still be there the following spring after an October application. That is not always a faulty sack. Do not answer it with a summer high-nitrogen feed. That mistake is on the autumn versus summer page. If the brown patches look like fungal rings rather than rake marks, there is no amateur fungicide for lawn diseases.

Common questions

Does autumn lawn feed kill moss?
Only if the pack says it does. In this set the granular Miracle-Gro listings claim iron or moss control, and they say moss blackens within seven days. The GreenCare liquids do not claim it. An autumn analysis such as 6-5-10 is about the grass. The iron is the moss part.
Why has the lawn gone black?
Because iron blackens moss, and the Miracle-Gro bullets say that happens within about seven days. It can also be scorched grass where the dose was heaped. If the black material rakes out and the grass remains, that matches the label. If you have bald soil and a visible pile of granules, you over-applied in that spot.
When do I rake?
After the moss has blackened, which these listings put at about two weeks, and Westland puts at about 14 days. Raking green moss first spreads it. Do not scarify the same afternoon you spread the granules.
The moss is still there in spring. Did it fail?
Not always. Reviews of the 360 m² bag include moss that remained after an October treatment when people looked again in spring. Shade, wet soil and a late or thin application all do that. A second autumn is the time to treat again, inside the two-applications-a-year cap, not a summer bag in March dressed up as a remedy.
Will the liquid seaweed feed kill moss?
No claim on these listings says it will. GreenCare is a seaweed liquid at 5 ml per litre, with no moss bullet. If the moss is the reason you are buying, you want an iron granule whose label says so, and you want to be able to keep pets off.
Is iron safe for dogs?
Follow the pack you have. Where these listings print a line, children and pets stay off until the granules are watered in and the lawn is dry. Do not shorten that because the granules look gone. If the bullets are silent, do not treat silence as a yes. If the dog cannot be kept off, do not use the iron pack.
Will moss come back in the shade?
Yes, if the shade, the wet and the low cut stay. The RHS says chemical control fails when the cause remains. Treat with iron before you scarify, or you spread spores, and do not seed the same week. Iron plus a rake buys a clearer lawn for a while. It does not move a tree.

Related pages

Autumn lawn fertiliser comparison

How to apply autumn lawn feed

Autumn lawn fertiliser buying guide

Autumn feed versus summer feed

Best autumn lawn feed UK: large lawn or small lawn

Sources

Public UK and maker sources from the research digest, used for this page in October 2026. Prices, stars and review counts are the nine amazon.co.uk listings in this comparison. Farming Rules for Water is an agricultural limit, not a householder statute. A pet line is quoted only where that listing prints it.

  1. RHS, lawn care in autumn (retrieved October 2026)
  2. RHS, lawns in October (retrieved October 2026)
  3. RHS, fertilisers (retrieved October 2026)
  4. RHS, fusarium patch and snow mould (retrieved October 2026)
  5. HSE, garden pesticides (retrieved October 2026)
  6. Miracle-Gro Autumn Lawn Care UK (retrieved October 2026)
  7. Miracle-Gro Autumn Lawn Care 360 m² pack label (retrieved October 2026)
  8. GOV.UK, Farming Rules for Water (retrieved October 2026)