Brand: Westland John Innes no 3 | Supplier: B&Q | Price: £0.17/litre
Personal observations
John Innes No. 3 is a formulation standard rather than a single product, and this is Westland’s interpretation — sand, loam and compost in the traditional proportions. The mineral content is immediately obvious: it feels dense and solid in the hand rather than light and fibrous. Two 5mm stones were visible after sieving, consistent with a green waste compost source for the organic fraction. No wood fibre fluff at all — completely different character to the mainstream Westland products. Water retention is among the lowest in the test at 1.6 times dry weight, which reflects the mineral content rather than being a fault — sand and clay hold less water per gram than fibre or compost. Drying took 30 minutes. The JI No. 3 formulation is genuinely useful for shrubs, trees and long-term container planting where the mineral fraction provides ballast and the slow-release nutrient content is appropriate. Comparing its water-retention figures directly to lighter peat-free mixes is not really meaningful — it is a different product for a different purpose.
Quick-test data (April 2026)
| Metric | Band | Value | Context |
|---|---|---|---|
| Bulk density (dry) | H | 0.32 g/ml | Heavy — mineral content (sand/clay) confirmed |
| Water held per g dry weight (WHC) | L | 1.6× | Low — expected given mineral fraction; not a performance defect |
| Dry-down time | — | 30 min | Moderate — mineral fraction slows surface evaporation |
| Sieve: <2mm fraction | — | 53.8% | Moderate fine fraction |
| Sieve: 2–10mm fraction | — | 39.6% | Moderate |
| Sieve: >10mm fraction | — | 5.0% | Low |
| Price per litre | Mainstream | £0.17 | B&Q retail — bought in store, no P&P |
Low WHC is inherent to the John Innes formulation — sand and clay minerals hold significantly less water per gram than organic matter. Direct comparison with peat-free organic composts on this metric is not meaningful. The mineral fraction provides structural ballast and slow nutrient release that organic-only products cannot match for long-term container planting.
B&Q in-store price only — purchasing online adds delivery cost and is not recommended for bulk compost. For an explanation of why brands offer multiple product types at different price points, see our FAQ.
Comparative hands-on testing, April 2026. Consistent method across all 18 products. See methodology note.
At-a-glance rating breakdown
| Category | Weight | Score |
| Ease of use | 40% | 6.6 |
| Composition & quality | 35% | 6.6 |
| Sustainability | 25% | 6.6 |
| Overall (weighted) | 100% | 6.6 / 10 |
What we liked
- Consistent, easy-to-handle product.
- Trusted brand familiarity.
Points to consider
- Limited biological depth.
- Requires feeding during use.
Material & sustainability note
Our conclusion
Overall impression: A dependable JI No3 – it’s not a multipurpose compost, more of a soil improver or total soil replacement.
