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Iron sulphate or sequestered iron for a lawn or shrub

Updated: October 2026

Iron sulphate or sequestered iron is the choice between greening a small lawn and helping a shrub on chalk. On this shelf they are not interchangeable. Ferrous sulphate is the lawn green-up, and it can blacken moss and stain stone. Sequestered iron is the short-term treatment for lime-induced chlorosis on shrubs. Aquarium iron is on the [iron fertiliser buying guide](/hub/fertiliser-soil-and-bark-mulch/iron-fertiliser/sub/iron-fertiliser-buying-guide). Prices are on the [iron fertiliser comparison](/hub/fertiliser-soil-and-bark-mulch/iron-fertiliser). Peter F., the DIY and tools editor, updated this on 21 October 2026 from those listings and from RHS and HSE guidance. This is not a laboratory test. A qualifying purchase can earn a commission at no extra cost to you.

Iron sulphate or sequestered iron is the choice between greening a small lawn and helping a shrub on chalk. On this shelf they are not interchangeable.

Our top picks

Doff Doff Sequestered Iron Plant Tonic

Best overall

Doff Doff Sequestered Iron Plant Tonic
7.3/10about £5.99
View offer
Maxicrop Maxicrop Sequestered Iron 500 ml

Rank 2

Maxicrop Maxicrop Sequestered Iron 500 ml
8.9/10about £7.14
View offer
Pro-Kleen Pro-Kleen Iron Sulphate 2.5 kg

Alternative

Pro-Kleen Pro-Kleen Iron Sulphate 2.5 kg
6.6/10about £16.95
View offer
On this page
  1. 1.Same element, different form
  2. 2.Ferrous sulphate on the lawn
  3. 3.Sequestered iron on the shrub
  4. 4.The lawn tub on a camellia
  5. 5.Black moss is not an authorisation

Same element, different form

Both supply iron, then they part company. Ferrous sulphate is the fast colour on turf, then the iron becomes hard for roots to use as pH rises. Sequestered iron stays available where chalk would lock it. ICL UK describes that split for professional turf. Their liquids are not in this comparison. Without EDTA, DTPA or EDDHA you cannot match a bottle to a pH band, and none of the shrub listings here prints that name. Yellow youngest leaves on a camellia put you on the sequestered side.

Ferrous sulphate on the lawn

Pro-Kleen iron sulphate granules, 2.5 kg at about £16.95, are ready to use, with up to 83 m² on the amazon.co.uk listing. The listing mentions magnesium and seaweed, claims up to three months if there is no frost, and warns that it may stain hard surfaces. There is no iron percentage and no MAPP number. Spread it dry. Some reviews saw darker moss, and one did not. That is not a pesticide, and it is not a feed for the rhododendron beside the grass. Steps are on how to apply iron fertiliser.
Doff Doff Sequestered Iron Plant Tonic

Testsieger

Doff Doff Sequestered Iron Plant Tonic
7.3/10about £5.99
View offer

Sequestered iron on the shrub

Maxicrop 500 ml at about £7.14 is sequestered iron with seaweed for acid-loving plants, with a Soil Association line for organic growing. Doff powder at about £5.99 is five 15 g packs. The 500 ml listing is the top pick from stars, reviews and price, not a laboratory. Which you prefer is on the best sequestered iron page, linked below. On chalk the RHS treats sequestered iron as short-term. Rhododendrons are at their best around pH 4.5 to 6.0. A yearly bottle in a chalk border is a bill for the wrong bed.

The lawn tub on a camellia

The ferrous sulphate tub on a yellow camellia is the expensive mistake. You wanted iron that stays available on a high pH. Pro-Kleen has a stain warning and no shrub rate, and it costs more in the wrong job than the about £7.14 concentrate. Some ferrous sulphate outside this comparison is sold for camellias. Free chalk is not usually treatable that way. A Maxicrop sheet and the Doff website mention a careful lawn line, so sequestered iron is not banned from grass. This page does not print those rates.

Black moss is not an authorisation

The RHS says blackened moss does not make a fertiliser a moss killer. Unless it is an approved proprietary moss killer, ferrous sulphate should not be used to control moss. The Health and Safety Executive expects an authorised garden pesticide. A lawn sand with a MAPP number sits outside this comparison. Raising the Pro-Kleen dose until the moss dies is not on the label. Use Pro-Kleen for a small lawn off paving, and Maxicrop or Doff for the shrub.

Common questions

Is iron sulphate the same chemical as sequestered iron?
No. Both contain iron, and the form after that is different. Iron sulphate is the usual fast green-up for lawns here, and it becomes hard for plants to use as pH rises. Sequestered iron is held so it stays available longer, which is why it is the shrub treatment on chalk. Read the form before you compare the price.
Can I use the lawn tub on a yellow camellia?
Not the Pro-Kleen tub in this comparison. It is ferrous sulphate for lawn green-up, with a stain warning and no shrub dose. A yellow camellia or rhododendron on chalk needs sequestered or chelated iron, and often ericaceous compost if you are feeding every year. Other ferrous sulphate products are not in this comparison.
Will sequestered iron green a lawn like ferrous sulphate?
Some sequestered labels include a careful lawn line, so sequestered iron is not banned from grass. That is still not the ready-to-use colour response people buy ferrous sulphate for, and this page does not print those rates. For a small lawn with up to 83 m² on the listing, Pro-Kleen is the match. For a camellia, stay with the sequestered bottle.
If moss turns black, is the fertiliser a moss killer?
No. Blackening can happen, and reviewers mention it, including one person who saw none. The RHS says fertiliser-only ferrous sulphate should not be used to control moss unless it is an approved moss killer. The Pro-Kleen listing has no MAPP number. Do not increase the dose to force a kill.
Which one stains paving, and which works on chalk?
The ferrous sulphate granules stain. Pro-Kleen's listing says they may mark hard surfaces, so brush them off while they are dry. Sequestered or chelated iron still supplies iron when chalk has locked it, and only for a time. A yearly need means lime-free compost in a container, or a different plant. For rhododendrons, the RHS band is about pH 4.5 to 6.0.
Why is the cheaper lawn tub the expensive mistake?
A damaged plant, or a stained patio, costs more than the gap between about £16.95 of granules and about £7.14 of shrub concentrate. If the camellia needed sequestered iron, the lawn tub was never the bargain. Buy the form that matches the job, then compare pack size inside that form.

Related pages

Best sequestered iron for a named job

Iron fertiliser

Iron fertiliser buying guide: choose the right form

How to apply iron fertiliser from the bottle label

Yellow leaves and iron deficiency on youngest growth

Sources

Public UK and maker sources from the research digest, used for this page in October 2026. Prices, stars and review counts are from the ten amazon.co.uk listings. A Soil Association line is an organic-growing claim, not a pet study. The Maxicrop 2% and 45 ml figures are from the professional sheet, not from the amazon mixing field. Chelate pH bands from a US extension summary are not UK law.

  1. RHS, nutrient deficiencies (retrieved October 2026)
  2. RHS, chalky soils (retrieved October 2026)
  3. RHS, moss in lawns (retrieved October 2026)
  4. GOV.UK, manufacturing and marketing fertilisers (retrieved October 2026)
  5. legislation.gov.uk, Regulation (EC) No 2003/2003, Article 9 (retrieved October 2026)
  6. HSE, garden and home pesticides (retrieved October 2026)
  7. Maxicrop professional iron sheet (retrieved October 2026)
  8. Easy-Life Ferro (retrieved October 2026)