Not every box is an NPK analysis
Garden centres put ‘tonic’, ‘invigorator’ and ‘rooting hormone’ next to Growmore. Read the SDS. Seaweed, chelated iron, Epsom, IBA and foliar soap solve specific jobs. Balanced 7-7-7 and tomato bottles live on the NPK guide.
If leaves yellow between veins on tomatoes, think magnesium. If rhododendrons yellow on chalk, think chelated iron — not lawn sand. If you are striking cuttings, think IBA in talc, not a feed.
Seaweed and foliar soap
Miracle-Gro Organic Liquid Seaweed is watered-down Ascophyllum nodosum (CAS 84775-78-0). Soluble kelp powder at about 5–20 g/L is the same crop. Foliar spray in still weather; it is a biostimulant, not a 20-20-20 stand-in.
SB Plant Invigorator is foliar urea plus alkyl / potassium soap that smothers aphids and mites. Bulk horticultural soft soap at about 10 ml/L with 5 g urea is the same working spray. Physical contact — repeat after rain. Do not mix with foliar copper.
Two irons, two jobs
Fe-EDDHA 6% (CAS 16455-61-1) stays available on alkaline soil — that is the Vitax sequestered-iron sachet. About 2 g/L (20 g in 10 L) as a root-zone drench. It can stain, but it is not rust-sulphate lawn sand.
Ferrous sulphate heptahydrate blackens moss and greens turf — Evergreen Complete 4-in-1 and similar lawn boxes. Mo Bacter is an iron-based moss story with a bacterial marketing layer. Keep soluble iron off pale stone. Sulphate of ammonia (21% N) is a nitrogen green-up, not a moss killer and not a chelate.
Epsom, meals and phosphate
Westland Epsom salts are MgSO4·7H2O — agricultural crystals, not a sleep supplement. Typical foliar is 10 g/L; soil around 20 g/m². Pair with a real tomato analysis if the plant is hungry for NPK.
Fish, blood and bone is a slow organic P-forward meal (Westland 3-9-3), not Growmore. Straight bone meal is steamed bone only (about 3.5-18-0) — phosphate without the blood-and-fish blend. Superphosphate is essentially 0-17-0 mineral phosphate for roots at planting. All three belong next to the NPK decoder, not in a moss-killer hopper.
IBA rooting powder is milligrams of hormone in talc
Doff-style 0.1% IBA (CAS 133-32-4) is about 75 mg of hormone in a 75 g tub of talc. 0.5 g of pure IBA dissolved in a splash of IPA, folded into 500 g of unscented talc, is the same 0.1% dip. Weigh on a milligram scale; keep away from children. This is a plant-growth regulator, not a fertiliser.
FAQ
- Is sequestered iron the same as Evergreen moss killer?
- No. Vitax sequestered iron is an EDDHA/EDTA chelate for yellowing lime-hating shrubs. Evergreen Complete and lawn sands use ferrous sulphate to blacken moss. Different iron chemistry, different stain risk on pale stone.
- Is Epsom salts a complete tomato food?
- No. Magnesium sulphate (CAS 10034-99-8) corrects magnesium. It is not Tomorite 4-3-8 and not BetterYou magnesium oil (that is chloride). See the NPK guide for complete feeds.
- Can I use SB Plant Invigorator instead of a pyrethroid?
- It is a different tool. SBPI-style sprays are dilute urea plus potassium soft soap that smothers soft-bodied insects. Deltamethrin (Provanto Ultimate) is a labelled insecticide. Do not treat soap as a substitute for an approved pesticide where the label requires one.
More lawn & garden guides
Lawn guide
Lawn and plant food labels decoded: NPK without the brand box
Lawn guide
Weedkillers decoded: glyphosate vs triclopyr — paths, brambles and lawn
Lawn guide
Lawn moss vs a nitrogen green-up — ferrous sulphate is not sulphate of ammonia
Lawn guide
Garden pests and disease: fungicides vs insecticides — not weedkillers
Related teardowns
Live stacks this guide points at — mix maths and DIY affiliate links on each page.
Lawn & garden
Miracle-Gro Organic Liquid Seaweed
Miracle-Gro
- Retail pack
- £13.501 litre
- Raw active
- Soluble Ascophyllum nodosum kelp powder84775-78-0
A watered-down cold-pressed kelp extract. Soluble Ascophyllum nodosum powder is the same crop, sold by the kilogram to hydroponic growers, at a fraction of the bottled price.
Lawn & garden
Sequestered Iron Plant Tonic
Vitax
- Retail pack
- £6.9980 g (4 × 20 g sachets)
- Raw active
- Fe-EDDHA 6% chelated iron (plus a pinch of Mg/Mn if you want the full tonic)16455-61-1
This is not ferrous sulphate (that is Evergreen moss killer) and it will not blacken a pale patio the same way. EDDHA/EDTA iron stays available on chalky soil. Four 20 g sachets are a tiny bag of the 6% chelate sold in 250 g tubs to nurseries.
Lawn & garden
Epsom Salts
Westland
- Retail pack
- £6.501.5 kg box
- Raw active
- Magnesium sulphate heptahydrate (Epsom salts)10034-99-8
The garden-centre box is agricultural Epsom salts with a picture of a tomato. MgSO4·7H2O is a commodity desiccant and bath salt. Buy it by the 5 kg bag, not 1.5 kg at a time. This is not BetterYou magnesium oil (that is chloride).
Lawn & garden
Natural Hormone Rooting Powder
Doff
- Retail pack
- £4.9975 g tub
- Raw active
- Indole-3-butyric acid (IBA)133-32-4
A 75 g tub is 74.9 g of talc carrying 75 mg of IBA. That is about £67/kg for cosmetic powder. 0.5 g of pure IBA in 500 g of unscented talc is the same 0.1% dip.
Lawn & garden
Plant Invigorator & Bug Killer
SB
- Retail pack
- £14.99500 millilitres
- Raw active
- Horticultural potassium soft soap57-13-6 / 61790-44-1
Dilute foliar urea plus a potassium fatty-acid soap that smothers soft-bodied insects. A 500 ml bottle at 10 ml/L makes about 50 litres; the same working spray from bulk soap and urea is pence per litre.
Lawn & garden
Sulphate of Ammonia
Westland
- Retail pack
- £7.501.5 kg box
- Raw active
- Agricultural ammonium sulphate 21% N7783-20-2
21% nitrogen as ammonium sulphate. The cardboard box is a portioned sack of a fertiliser merchants sell in 25 kg lots. It greens grass. It also acidifies — do not pile it on chalk-hating stone paths.
Lawn & garden
Evergreen Complete 4-in-1 Lawn Feed & Moss Killer
Evergreen
- Retail pack
- £24.00100 m² box
- Raw active
- Agricultural soluble iron(II) sulphate heptahydrate7782-63-0
The moss-blackening punch is ferrous sulphate — the same agricultural iron used on bowling greens. The 4-in-1 box is mostly filler, NPK dust and a brand. Buy the salt.
Lawn & garden
Organic Lawn Moss Killer & Fertiliser
Mo Bacter
- Retail pack
- £38.0020 kg bag
- Raw active
- Sulphate of potash (0-0-50)7778-80-5
The moss dies because of high potash, not a magic organic patent. Sulphate of potash (0-0-50) supplies the same K2O without iron staining; a cheap Bacillus or compost-tea inoculant does the digestion step. A 20 kg 5-5-20 bag is mostly filler next to 10 kg of 50% K2O.
Lawn & garden
Fish, Blood & Bone
Westland
- Retail pack
- £5.491.5 kg box
- Raw active
- Fish, blood and bone meal (25 kg; typically 5-5-6 or 3-9-3)N/A - Organic Blend
This is not Growmore 7-7-7. It is an organic P-forward meal. Westland’s garden powder is 3-9-3 and, on the SDS, roughly half silica dust. A 25 kg sack of fish, blood and bone is the same job without the 1.5 kg box tax — check the analysis; trade bags are often 5-5-6.
Lawn & garden
Bone Meal
Westland
- Retail pack
- £5.491.5 kg box
- Raw active
- Steamed bone meal (agricultural, ~3.5-18-0)68476-17-1
Westland’s 1.5 kg box is steamed bone meal — slow organic phosphate (typically about 3.5-18-0), not Growmore 7-7-7, not superphosphate 0-17-0, and not Fish, Blood & Bone (a three-meal blend). A 25 kg agricultural sack is the same ground bone. CAS 68476-17-1 is the meal, not a secret rooting hormone.
Lawn & garden
Superphosphate
Westland
- Retail pack
- £6.991.5 kg box
- Raw active
- Triple superphosphate 46% P2O5 (or 17% as labelled granules)7758-87-4
A phosphorus-forward 0-17-0 — not Growmore 7-7-7, not fish blood and bone meal. Superphosphate is triple superphosphate granules sold in a small box. Merchants sell the same 17% P2O5 sack by the 25 kg for root establishment and autumn planting.
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