# What soil should I use for growing cannabis?

> The best soil for growing cannabis indoors is a quality bagged potting mix, peat- or coco-based with compost and a light starter fertiliser, opened up with 20–35% perlite or pumice. Never use garden soil in pots. The starter charge feeds for 2–4 weeks; after that, feed at EC 0.8–1.6 mS/cm with water at pH 6.2–6.8.

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- Topic: Systems · Type: How-to
- Evidence: Supported · 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: What is the best soil mix for cannabis? | Can I use normal potting soil for weed? | Do I need perlite in soil? | Can I use hydro nutrients in soil? | Can I use garden soil in pots?
- 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

Use a quality bagged [potting mix](https://genetixbay.com/knowledge/glossary/potting-mix.md), peat- or coco-based with compost and a light starter fertiliser, and add 20–35% [perlite](https://genetixbay.com/knowledge/glossary/perlite.md) or pumice. Don't use garden soil in pots. The starter charge feeds a plant for about 2–4 weeks; then feed at [EC](https://genetixbay.com/knowledge/glossary/ec.md) 0.8–1.6 [mS/cm](https://genetixbay.com/knowledge/glossary/ms-cm.md) with water at [pH](https://genetixbay.com/knowledge/glossary/ph.md) 6.2–6.8. *Supported* for the container physics; brand choice matters far less than [drainage](https://genetixbay.com/knowledge/glossary/runoff.md).

## Why

Indoor "soil" is really potting mix. It has three jobs: hold water, hold air and hold nutrients on its exchange sites. Compost and [peat](https://genetixbay.com/knowledge/glossary/peat.md) buffer pH, which is why soil forgives small mistakes.

Air matters as much as water. A dense mix stays saturated, roots run short of oxygen and the plant wilts in wet soil [1]. Perlite or pumice adds large pores that drain and refill with air.

Garden soil compacts in a container and can carry [damping-off](https://genetixbay.com/knowledge/glossary/damping-off.md) and root-rot organisms [2].

Organic or mineral feeding both work. Cannabis grew well in organic, coir-based media once nitrogen supply was high enough [3]; the plant mostly doesn't care where its ions come from.

## The numbers

| Item | Target |
|---|---|
| Base | Peat- or coco-based potting mix with compost |
| Perlite or pumice | 20–35% of volume, mixed through |
| Starter charge lasts | About 2–4 weeks |
| Irrigation pH | 6.2–6.8 (soil range 6.0–7.0) |
| Feed EC, once charge runs out | 0.8–1.6 mS/cm (400–800 [ppm500](https://genetixbay.com/knowledge/glossary/ppm500.md) / 560–1,120 [ppm700](https://genetixbay.com/knowledge/glossary/ppm700.md)) |
| [Pot size](https://genetixbay.com/knowledge/glossary/pot-size.md), [photoperiod](https://genetixbay.com/knowledge/glossary/photoperiod.md) | 11–25 L (3–7 US gal) |
| Pot size, [autoflower](https://genetixbay.com/knowledge/glossary/autoflower.md) | 11–15 L (3–4 US gal), planted directly |

## What to do

1. Buy a mix labelled for containers; avoid "moisture control" mixes with wetting gels.
2. Add 20–35% perlite or pumice and mix it through evenly.
3. Water with plain, pH-adjusted water while the starter charge lasts.
4. Start feeding at half the label rate when lower leaves begin to pale.
5. Check runoff EC and pH monthly; if runoff EC climbs well above input, do a [root-zone flush](https://genetixbay.com/knowledge/glossary/root-zone-flush.md) with 2–3× the pot volume.

## Common mistakes

- Garden soil or topsoil in pots.
- A hot, heavily fertilised mix for [seedlings](https://genetixbay.com/knowledge/glossary/seedling.md), which burns them.
- Hydro-strength feed on top of a fertilised mix.
- A gravel layer at the bottom instead of perlite through the mix.

## Related

- Full article: [Growing in soil](https://genetixbay.com/knowledge/systems/soil.md)
- Answers: [when soil runs out of nutrients](https://genetixbay.com/knowledge/answers/when-does-soil-run-out-of-nutrients.md) · [mixing soil and coco](https://genetixbay.com/knowledge/answers/can-i-mix-soil-and-coco.md) · [super soil](https://genetixbay.com/knowledge/answers/what-is-super-soil.md) · [reusing soil](https://genetixbay.com/knowledge/answers/can-i-reuse-soil.md)
- Terms: [potting mix](https://genetixbay.com/knowledge/glossary/potting-mix.md) · [perlite](https://genetixbay.com/knowledge/glossary/perlite.md)

## Follow-up questions

**Do I need to add perlite to potting soil?** Yes, add perlite or pumice to potting soil for cannabis, at about 20–35% of the volume. Most bagged mixes are made for small houseplants and hold too much water for a big, thirsty plant in a deep pot. Extra perlite raises air space so roots get oxygen between waterings. Mix it evenly through the whole pot, never as a bottom layer.

**Can I use hydro nutrients in soil?** You can use hydro mineral nutrients in soil, but only at soil strength. Wait until the mix's starter charge runs out, usually 2–4 weeks, then start at half the label rate and feed at EC 0.8–1.6 mS/cm every second or third watering. Check runoff EC monthly, because a rising reading means salts are building up in the pot.

**Can I use garden soil for cannabis in pots?** No, don't use garden soil in pots. Garden soil compacts in a container, drains poorly and starves roots of air, and it can carry pathogens that cause damping-off and root rot. Outdoors in the ground, native soil can work well once amended. Indoors, use a bagged potting mix with added perlite or pumice.

## Sources

1. Raviv M, Lieth JH, Bar-Tal A (eds), 2019. Soilless Culture: Theory and Practice, 2nd ed. Elsevier (container media physics and air-filled porosity). https://doi.org/10.1016/C2015-0-01807-5
2. University of Minnesota Extension. How to prevent seedling damping off (sanitation; avoid garden soil in containers). https://extension.umn.edu/solve-problem/how-prevent-seedling-damping
3. Caplan D, Dixon M, Zheng Y, 2017. Optimal rate of organic fertilizer during the vegetative-stage for cannabis grown in two coir-based substrates. HortScience 52(9):1307–1312. https://doi.org/10.21273/HORTSCI12401-17