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Iron blackens moss in days; it does not fix why it was there

Lawn moss killers, compared

Moss in a lawn is a symptom: compaction, shade, poor drainage or grass too weak to compete. Every product on this shelf treats the symptom, and the honest ones say so on the pack. The active substance is almost always iron — iron(II) sulphate — which blackens moss within days and is also a nutrient, which is why half this corpus is sold as a combined fertiliser-and-moss product rather than a treatment alone. The form follows: granules spread dry, or a concentrate diluted and sprayed. The weight and coverage pair works exactly as it does on fertiliser, and the rate is on the pack. Two columns here exist for reasons that are legal rather than agronomic. The waiting time — how long before the lawn may be walked on, mown, or used by pets and children — is published because it is part of the authorised use, and it is the single most practical thing on the label. And the approval: products that make a pesticidal claim are authorised, carry a registration number and are sold under conditions that vary by country. A fertiliser with iron in it and an authorised moss herbicide are not the same category of product even when they look identical on the shelf, and this site reports what each label states without recommending either. The rest is what happens afterwards: dead moss is a black mat that has to be raked or scarified out, and the bare ground it leaves has to be seeded or the moss returns to the same place. We compare weight, coverage, active, form, waiting time and approval.

Every part here, laid out figure by figure

  1. Iron sulphate lawn fertiliser and moss treatment

    LERAVA 2-5

    An iron fertiliser for grass — the only product here with no weight published, and the dearest square metre.

    Weight
    Not published
    Coverage
    20 m². No weight is published, so no application rate can be worked out.
    Active
    Iron sulphate, with potassium and magnesium; no percentages published
    Form
    Granular iron sulphate, evenly spreadable
    Waiting time
    Stated as usable all year round
    Approval
    On lawns, all lawn types
    Amazon reference
    B0D3QRCZ1Y (one reference across 5 Amazon marketplaces)
    EAN
    4260771321995
    • A plainly named active — iron sulphate — which two of the three lawn products here do not give
    • Names potassium and magnesium alongside the iron
    • No weight published, so the application rate cannot be established

    Best for: A small mossy patch, applied carefully and well away from paving

    Check price on Amazon
  2. One litre concentrate for removing green deposits from stone and paving

    Prinox MX067

    A hard-surface biocide concentrate at 1:20 — NOT for lawns — with a spray bottle and measure included.

    Weight
    1 L of concentrate
    Coverage
    1:20 for light growth, 1:10 for heavy; 1 bottle for up to 125 m²
    Active
    Not named; stated chlorine-free and acid-free
    Form
    Liquid concentrate; a 500 ml mixing bottle with a spray head and a measuring cup are supplied
    Waiting time
    Apply to dry surfaces; leave 3–4 days, then rinse off; long-term effect claimed up to 12 months
    Approval
    Facades, roofs, terraces, paving, wood, concrete, natural stone, plastic, awnings, gravestones, garden furniture — all water-tolerant surfaces. NOT lawns.
    Amazon reference
    B0DVXT698H (one reference across 1 Amazon marketplace)
    EAN
    4260760852240
    • The most dilute concentrate here — 1:20 at the light setting, and the lowest cost per square metre
    • A 500 ml mixing bottle with a spray head and a measuring cup are included
    • Not for lawns — on grass this kills grass

    Best for: A green patio, a north-facing wall or a shaded path — never a lawn

    Check price on Amazon
  3. One litre green deposit remover concentrate for stone and wood

    VEXIL V10008

    A hard-surface biocide that publishes how long each organism takes — and its registration number.

    Weight
    1 L of concentrate
    Coverage
    1:10 light — 1 L for 100 m²; 1:5 heavy — 1 L for 50 m²
    Active
    Not named; stated free of acid and chlorine. Registration number BAuA N-114607 published.
    Form
    Liquid concentrate
    Waiting time
    Algae 2–3 days; moss 1–3 weeks; stubborn lichen 3–12 months
    Approval
    Facades, garden furniture, gravestones, ornamental stone, terraces, wood, plastic, concrete, natural stone, glass, ceramic, PVC. NOT lawns.
    Amazon reference
    B0F168P7DV (one reference across 1 Amazon marketplace)
    EAN
    4262440110466
    • Publishes a timescale for each organism separately, which is the honest way to sell this
    • Publishes a biocide registration number and the statutory use warning
    • Not for lawns — on grass this kills grass

    Best for: A green terrace or facade, treated once and left alone for a month

    Check price on Amazon
  4. WOLF Garten SW 100 moss killer and lawn fertiliser

    WOLF Garten SW 100

    The only product here that publishes its iron content — 6 % — with 14 % nitrogen, for 100 m².

    Weight
    3.5 kg
    Coverage
    3.5 kg for 100 m² — 35 g/m²
    Active
    14 % nitrogen, 5 % potassium oxide, 6 % iron — the only iron figure on this shelf
    Form
    Granular: 14 % nitrogen, 5 % potassium oxide, 6 % iron
    Waiting time
    February to October; moss cleared in 2–3 weeks; deep green in 7 days
    Approval
    On lawns
    Amazon reference
    B01MYTIO5Q (one reference across 4 Amazon marketplaces)
    EAN
    4008423875560
    • The only published iron content on this shelf, at 6 %
    • A full declaration — nitrogen, potassium and iron, with a matching weight and coverage
    • 6 % iron will stain concrete, stone and paving permanently

    Best for: A mossy lawn in spring, treated well away from every hard surface

    Check price on Amazon
  5. Five litre canister of green deposit and moss remover concentrate

    Treufix 01

    Five litres of concentrate diluted 1:2 at its weakest and used undiluted at its strongest — for hard surfaces.

    Weight
    5 L of concentrate
    Coverage
    1:2 light, 1:1 medium, undiluted for heavy; 5 L supplied. No area published.
    Active
    Not named. Registration number BAuA N-116020 published, with the statutory use warning.
    Form
    Liquid concentrate
    Waiting time
    Algae 2–3 days; moss 3–6 weeks; lichen 3–12 months. Surface must be dry and stay rain-free 24 h.
    Approval
    Gravestones, roofs, wooden fences, terraces, roof tiles, facades, paving, driveways. NOT lawns.
    Amazon reference
    B0D8BPFTKP (one reference across 1 Amazon marketplace)
    EAN
    4262387270377
    • The only listing here that says to remove heavy moss mechanically first
    • Publishes its registration number, the statutory warning, and separate timings per organism
    • Not for lawns — on grass this kills grass

    Best for: A badly overgrown north-facing terrace or roof, scraped first and then treated

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  6. Neudorff moss and weed stop lawn fertiliser 10 kg

    Neudorff 01238

    An organic-mineral feed with extra iron, sold on the argument that a dense lawn needs no scarifying.

    Weight
    10 kg
    Coverage
    10 kg for 200 m²; stated rate 50 to 80 g/m²
    Active
    NPK 8-4.5-13 plus an extra portion of iron; no iron percentage published
    Form
    Organic-mineral granule, NPK 8-4.5-13 with added iron
    Waiting time
    Spring, summer and autumn; mow to 4–5 cm first and apply to a moist lawn
    Approval
    On lawns, including lawns maintained by a robot mower
    Amazon reference
    B01BPLG8YO (one reference across 5 Amazon marketplaces)
    EAN
    4005240012383
    • Publishes a full NPK, which only one other lawn product here does
    • Gives the preparation properly — mow to 4–5 cm, apply to moist grass
    • No iron percentage, and iron stains hard surfaces permanently

    Best for: A lawn being brought back over a season rather than treated once

    Check price on Amazon
  7. COMPO complete care lawn fertiliser with weed and moss killer

    Compo 26173

    The only plant protection product here — once a year, May to August, above 10 °C, lawn unusable for days.

    Weight
    9 kg
    Coverage
    9 kg for 300 m² — 30 g/m²
    Active
    Not named; described as containing a weedkiller and a moss killer, with all main and trace nutrients
    Form
    Homogeneous fine granule, stated to dissolve quickly
    Waiting time
    At most once a year, May to August, above 10 °C; apply to dew-wet lawn 1–2 days after mowing; do not use the lawn for 2–3 days
    Approval
    On established lawns only — NOT in the year of sowing
    Amazon reference
    DE B00UT2LM2O · ES B00U65S5BU
    EAN
    4008398261733
    • The only product here that treats broadleaved weeds as well as moss
    • Publishes a complete application protocol — timing, temperature, sequence and re-entry
    • A plant protection product, with an annual limit and an exclusion period — unlike everything else here

    Best for: An established lawn with both moss and broadleaved weeds, treated once in summer

    Check price on Amazon