Lawn & garden
Westland Superphosphate dupe
Why pay around £6.99 for Westland? The bulk active is Triple superphosphate 46% P2O5 (or 17% as labelled granules) — 70% less per working litre than a typical shelf pack.
From the retail pack to the active and the mix
1 · Retail
Westland Superphosphate
1.5 kg box · £6.99 typical snapshot
Granular carrier
2 · Active
Superphosphate (calcium phosphate, 17% P2O5)
17% on the label
7758-87-4Ca(H2PO4)2
Bulk Triple superphosphate 46% P2O5 (or 17% as labelled granules)
3 · Mix
70 g/m² at planting
£0.05 per working litre · 70% less than the shelf pack
- Active
- Superphosphate (calcium phosphate, 17% P2O5)
- CAS
- 7758-87-4
- Dupe
- Triple superphosphate 46% P2O5 (or 17% as labelled granules)
- Saving
- 70% / L
Saving is per litre of working-strength mix versus a typical pack price, not versus the DIY kit total. Shop prices move — always check the listing.
Label teardown
What the pack promises versus what the label chemistry actually is.
The marketing claim
“Encourages strong root development”
The chemical reality
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.
Active vs filler
17% Superphosphate (calcium phosphate, 17% P2O5) · 83% carrier / filler — Granular carrier
- Typical retail
- £6.99
- 1.5 kg box
- Estimated active cost
- £0.42
- Scaled from bulk £19.00 / 25 kg
- Indicative markup
- 16.6×
- Snapshot maths, not a live shop price
The Marketing Claim & The Catch
A 1.5 kg box pack of Westland Superphosphate typically retails around £6.99 in lawn & garden. That is a UK shelf-price snapshot for the maths on this page — not a live shop quote or a manufacturer RRP. Listings, sizes and deals move. The marketing line is that you are buying a finished lifestyle product, not a weighed chemical.
On the pack: Encourages strong root development; Ideal for new plants, fruit and vegetables; and Ready to use granules.
The catch: 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.
- “Encourages strong root development”
- “Ideal for new plants, fruit and vegetables”
- “Ready to use granules”
Proprietary Blend & Dosage Breakdown
The labelled active is Superphosphate (calcium phosphate, 17% P2O5) at 17%. Everything else in the pack is granular carrier.
At 17% active, most of what you pay for is carrier and packaging. The brand is selling convenience, fragrance and a label — not a uniquely potent molecule.
Branded working strength is whatever comes out of the bottle. The bulk alternative is 46% Triple superphosphate 46% P2O5 (or 17% as labelled granules), mixed to 70 g/m² at planting.
- Labelled active
- Superphosphate (calcium phosphate, 17% P2O5)
- 17%
- Carrier
- Granular carrier
- Retail pack
- 1.5 kg box · £6.99
The Active Chemical Alternative (Dupe Stack)
The dupe stack is Triple superphosphate 46% P2O5 (or 17% as labelled granules) at 46% bulk. Indexed as CAS 7758-87-4, formula Ca(H2PO4)2. Buy it as 25 kg for around £19.00 from Amazon UK.
Working strength: 70 g/m² at planting. Indicative cost £0.05 per diluted litre — 70% below a typical branded pack on a per-litre basis, before you reuse leftover bulk.
Follow the mixing method and the supplier SDS. Wear the listed PPE. Do not mix incompatible oxidisers, acids or ammonia.
- Dust: gloves and FFP2 mask when handling dry granules. Keep off ponds.
- At planting: 70 g per m² forked into the top 15 cm, or a teaspoon in the planting hole for individual shrubs.
- A 25 kg sack at 70 g/m² covers about 350 m². The 1.5 kg box is roughly 21 m².
- Store dry. Phosphate is immobile in soil — work it in where roots will reach it.
Dilution recipe
5 L sprayer
Working strength 70 g/m² at planting. Educational estimate from the listed ratio — check the SDS before you mix.
Chemical
7,000 grams
Triple superphosphate 46% P2O5 (or 17% as labelled granules)
Water
5 litres
Carrier / diluent
0% concentrate · 100% water by working volume (solids are dissolved into the water share).
Required PPE
Loading calculator…
Side-by-Side Price & Potency Comparison
Head-to-head comparison
| Measure | Retail brandedWestland | Raw active dupeDupeStack |
|---|---|---|
| Product | SuperphosphateAmazon UK search — listing, not a confirmed seller | Triple superphosphate 46% P2O5 (or 17% as labelled granules) |
| Pack / unit | 1.5 kg box · £6.99 | 25 kg · £19.00 |
| Active | Superphosphate (calcium phosphate, 17% P2O5) at 17%Carrier: Granular carrier | 46% bulkCa(H2PO4)2 |
| CAS number | Not disclosed on pack | 7758-87-4 |
| Working strength | Ready-to-use pack | Dilute 70 g/m² at planting |
| Cost per litre | £6.99 / pack | £0.05 / L mixed from bulk |
| Headline saving | Baseline | 70% cheaper |
| COSHH / PPE | Follow the branded SDS | Gloves. Chemical-resistant gloves (nitrile or neoprene)Respirator. Rated respirator for dusts or vapours as specified on the SDS |
Active ingredient and cheaper alternative — FAQ
Is superphosphate the same as Growmore?
No. Growmore is balanced 7-7-7 NPK. Superphosphate is essentially phosphate with negligible nitrogen — a root and establishment feed, often used at planting or in autumn on bare-root stock.
Can I use it on the lawn like sulphate of ammonia?
Wrong tool. Sulphate of ammonia is quick nitrogen for green-up. Superphosphate is for roots and phosphate-hungry crops — not a moss killer and not a lawn sand substitute.
How do you mix the Superphosphate dupe stack?
Dust: gloves and FFP2 mask when handling dry granules. Keep off ponds. At planting: 70 g per m² forked into the top 15 cm, or a teaspoon in the planting hole for individual shrubs. A 25 kg sack at 70 g/m² covers about 350 m². The 1.5 kg box is roughly 21 m². Store dry. Phosphate is immobile in soil — work it in where roots will reach it.
DupeStack provides chemical concentration data and educational mixing guides only. Wellness pages compare food supplements, not medicines or prescribed treatments. Always review the supplier Safety Data Sheet (SDS) and comply with UK Health and Safety Executive (HSE) and COSHH regulations when handling concentrated substances. Mixing and storage are at your own risk. Some links are affiliate advertisements (Amazon Associates, eBay Partner Network, and Awin when those programmes are live). Commissions do not change listed concentrations or calculator output.
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£35.00Save 70% / L
Indicative DIY stack