# Can I reuse soil from my last grow?

> Yes, you can reuse soil from your last grow if the plants were healthy. Break up the root ball, add fresh compost or worm castings, slow-release organic amendments and perlite, then keep it moist for 2–4 weeks before planting. Don't reuse soil from plants with root rot, wilt or root pests. Coco can be rinsed and re-buffered; living soil is reused in place, no-till.

- Canonical: https://genetixbay.com/knowledge/answers/can-i-reuse-soil.html
- Topic: Systems · Type: How-to
- Evidence: Grower practice · Status: Draft: awaiting expert review
- Full article: [Growing in soil (potting mix with bottled feed)](https://genetixbay.com/knowledge/systems/soil.md)
- Also asked as: Can I reuse potting soil for cannabis? | How do I recycle old grow soil? | How do I amend old soil for the next run? | Can I reuse coco coir?
- Updated: 2026-10-31 · Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay Knowledge Base (genetixbay.com/knowledge)"

## Short answer

Yes, reuse soil from a healthy grow. Break up the root ball, mix in fresh compost or worm castings, slow-release [organic amendments](https://genetixbay.com/knowledge/glossary/organic-fertiliser.md) and [perlite](https://genetixbay.com/knowledge/glossary/perlite.md), and keep it moist for 2–4 weeks before planting. Don't reuse soil from plants with [root disease](https://genetixbay.com/knowledge/glossary/root-rot.md) or root pests. *Grower practice*, consistent with established soil-health principles.

## Why

A finished run leaves the mix depleted, not ruined. The plant used up the starter charge, and the [peat](https://genetixbay.com/knowledge/glossary/peat.md) or [coco](https://genetixbay.com/knowledge/glossary/coco-coir.md) has broken down a little, so the mix holds more water and less air [4].

Old roots are food. Left in the mix, they decompose and feed soil life, and keeping soil covered and biologically active is a core soil-health principle [1].

The danger is disease. [Fusarium](https://genetixbay.com/knowledge/glossary/fusarium-wilt.md), [Pythium](https://genetixbay.com/knowledge/glossary/pythium.md) and similar pathogens survive in old roots and media [2][3]. Soil from a sick crop carries them into the next one.

[Living soil](https://genetixbay.com/knowledge/glossary/living-soil.md) goes further: it isn't emptied at all. Stems are cut at the surface, roots stay, and the bed is top-dressed and replanted ([no-till](https://genetixbay.com/knowledge/glossary/no-till.md)) [1].

## The numbers

| Step | Amount or time |
|---|---|
| Fresh compost or worm castings | About 20–30% of volume |
| Extra perlite or pumice | 10–20% to restore [air space](https://genetixbay.com/knowledge/glossary/air-filled-porosity.md) |
| Slow-release organic amendment | Label rate for the volume |
| Rest, moist and warm | 2–4 weeks before planting |
| Coco: rinse | To [runoff](https://genetixbay.com/knowledge/glossary/runoff.md) [EC](https://genetixbay.com/knowledge/glossary/ec.md) below about 0.5 [mS/cm](https://genetixbay.com/knowledge/glossary/ms-cm.md), then re-buffer |
| Pot disinfection | 10–15% household bleach solution [2] |

## What to do

1. Check the last crop. Any root rot, wilt or [root aphids](https://genetixbay.com/knowledge/glossary/root-aphid.md): bag and discard the soil.
2. Dry the old mix slightly, crumble it and pull out the large root masses.
3. Mix in compost or castings, perlite and a slow-release amendment.
4. Rehydrate, cover and leave it warm and moist for 2–4 weeks.
5. Plant, water with plain water, and feed only when lower leaves begin to pale.
6. Wash pots and trays. Wear gloves and eye protection with bleach, and never mix it with acids or ammonia.

## Common mistakes

- Reusing soil from a crop that wilted or had brown roots.
- Planting [seedlings](https://genetixbay.com/knowledge/glossary/seedling.md) straight into freshly amended "hot" soil.
- Reusing the same mix for many runs without restoring air space.
- Sterilising healthy soil and killing its biology.

## Related

- Full article: [Growing in soil](https://genetixbay.com/knowledge/systems/soil.md)
- Answers: [what is super soil](https://genetixbay.com/knowledge/answers/what-is-super-soil.md) · [best soil for cannabis](https://genetixbay.com/knowledge/answers/best-soil-for-cannabis.md) · [when soil runs out of nutrients](https://genetixbay.com/knowledge/answers/when-does-soil-run-out-of-nutrients.md)
- Systems: [living soil](https://genetixbay.com/knowledge/systems/living-soil.md)
- Terms: [top-dressing](https://genetixbay.com/knowledge/glossary/top-dressing.md) · [no-till](https://genetixbay.com/knowledge/glossary/no-till.md)

## Follow-up questions

**Do I need to sterilise old soil before reusing it?** No, you don't need to sterilise old soil from a healthy grow, and doing so kills the beneficial organisms you want. Sterilising or pasteurising only makes sense if the last crop had root disease, and then discarding the soil is usually simpler. Instead, re-amend it with compost and nutrients, rehydrate it and let it rest moist and warm for 2–4 weeks.

**Can I reuse soil from plants with root rot or pests?** Don't reuse soil from plants that had root rot, Fusarium wilt, root aphids or a heavy fungus gnat infestation. These organisms survive in old roots and media and will attack the next crop. Bag the soil and dispose of it away from the grow, then wash pots and trays and disinfect them with a 10–15% household bleach solution before reuse.

**Can I reuse coco coir?** Yes, coco coir can be reused after a healthy run. Remove as much root mass as you can, rinse until runoff EC is below about 0.5 mS/cm, and re-buffer it with a calcium-magnesium solution before replanting. Root debris raises water holding and disease risk, so add some fresh coco and perlite, and don't reuse coco more than a couple of times.

## Sources

1. USDA Natural Resources Conservation Service. Soil health principles (minimise disturbance, keep soil covered, maintain living roots, maximise biodiversity). https://www.nrcs.usda.gov/conservation-basics/natural-resource-concerns/soil/soil-health
2. Utah State University Extension. Fusarium Wilt (hemp). https://extension.usu.edu/planthealth/ipm/notes_ag/hemp-fusarium-wilt
3. Punja ZK, et al., 2019. Pathogens and Molds Affecting Production and Quality of Cannabis sativa L. Frontiers in Plant Science 10:1120. https://doi.org/10.3389/fpls.2019.01120
4. Raviv M, Lieth JH, Bar-Tal A (eds), 2019. Soilless Culture: Theory and Practice, 2nd ed. Elsevier (organic substrates and compost chapters). https://doi.org/10.1016/C2015-0-01807-5