Soil Conditioners

Soil conditioners

Build the soil first

A soil conditioner is a material added to the soil to improve its physical structure, biology, drainage, aeration and long-term fertility, distinct from a fertiliser, which mainly feeds the plant. Use soil conditioners as your foundation: build the soil first, and your fertilisers work harder for less. This range covers the conditioners UK growers ask for most, including volcanic rock dust, biochar, montmorillonite clay and kelp meal. The Dr Forest range is curated for UK no-dig, organic and living soil growers, with products made with organic ingredients sourced for their proven performance.

What's in this collection

  • Volcanic rock dust (basalt): both granulated and micronised forms. A slow-release source of more than 60 minerals, used to remineralise depleted soils.
  • Calcium amendments: micronised calcium carbonate (Cal-Carb), sea shell meal and Antarctic krill meal for slow-release calcium, structure and gentle pH correction.
  • Clay minerals: montmorillonite clay to boost cation-exchange capacity (CEC), water retention and microbial habitat in light or sandy soils.
  • Carbon and biology: raw wood biochar to permanently lock in moisture, nutrients and microbes; malted barley to fuel beneficial fungi and accelerate decomposition.
  • Marine inputs: Scottish kelp meal for trace elements and natural growth promoters.
  • Microbial conditioners: Grow-Kashi probiotic top-dress and a multi-mineral micro-nutrient mix.

Why every UK garden needs them

  • Break up compacted clay and bind sandy soils into something better-structured.
  • Hold more water: fewer waterings, better drought resilience.
  • Improve aeration and drainage so roots can breathe.
  • Feed earthworms, fungi and bacteria: the engine of organic gardening.
  • Improve flavour and nutrition in fruit and vegetables grown in living soil.
  • Build long-term fertility that lasts seasons, not weeks.

How and when to apply

Apply when preparing beds in spring or autumn, when potting on, or as a yearly top-dress. Most conditioners in this range are slow-release: a single application can support soil structure for one to three years.

Want to dig deeper? Read our guide to volcanic rock dust, or pair these conditioners with humic acid for the strongest soil-building results.

Soil conditioners: common questions

No. Fertilisers feed the plant; soil conditioners improve the soil itself. Use them together for best results.
Once a year is usually enough, typically in autumn or early spring. Rock dust is a slow-release amendment.
Yes. Every conditioner in this range is suitable for no-dig and living soil systems. Apply as a top-dress.
Yes, especially when combined with compost or worm castings to "charge" it first. Biochar opens up clay structure and provides permanent microbial habitat.
Both are stocked in this collection and shipped across the UK from Stockport. You'll find granulated and micronised volcanic rock dust alongside raw wood biochar, kelp meal and montmorillonite clay.