# My buds got mouldy in the jar: what now?

> Mouldy buds in a curing jar must be thrown away, not trimmed and smoked. Mouldy flower carries spores and possible mycotoxins. Bin every bud with fuzz, grey dust or brown inner tissue, then open every other jar and check it. Spread the rest out to dry until a sealed sample reads a stable 55–65% RH (water activity 0.55–0.65). Jar mould usually means buds went in too wet.

- Canonical: https://genetixbay.com/knowledge/answers/mould-in-curing-jars.html
- Topic: Diseases · Type: Troubleshooting
- Evidence: Established · Status: Draft: awaiting expert review
- Full article: [Botrytis (bud rot / grey mould) in cannabis](https://genetixbay.com/knowledge/diseases/botrytis-bud-rot.md)
- Also asked as: Mould in my curing jars | Moldy buds after cure: can I save them? | Fuzzy buds in the jar | White fuzz on buds in jar
- 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

If buds in a [curing jar](https://genetixbay.com/knowledge/glossary/curing-jar.md) have gone mouldy, throw them away. Don't trim around the mould and don't smoke them. Then check every other jar, and dry the clean buds until a sealed sample reads a stable 55–65% [RH](https://genetixbay.com/knowledge/glossary/relative-humidity.md) ([water activity](https://genetixbay.com/knowledge/glossary/water-activity.md) 0.55–0.65). *Established*: mouldy flower isn't safe to smoke, vape or extract.

## Why

Mouldy cannabis can carry spores and mycotoxin-producing fungi, which is why regulated markets test flower for yeast and mould [1].

Mould grows when the bud's water activity is too high. ASTM sets 0.55–0.65 aw as the safe range for dried flower, and says flower above 0.68 needs more drying [2][3]. A jar holds in whatever moisture is still in the bud cores.

[Botrytis](https://genetixbay.com/knowledge/glossary/botrytis.md) can also come in from the plant. It rots dense [colas](https://genetixbay.com/knowledge/glossary/cola.md) from the inside, often before anything shows, when late-flower humidity is high or water condenses at lights-off [4]. Buds infected that way can rot in the jar even when the dry looked right.

## The numbers

| Reading | Meaning | Action |
|---|---|---|
| Sealed jar, stable 55–65% RH | aw 0.55–0.65, safe [2] | Keep curing |
| 65–68% RH | Borderline | Take the buds out and dry them more |
| > 68% RH, or 75%+ overnight | Too wet [3] | Dry them now and watch for mould |
| Fuzz, grey dust, brown core | Mould | Throw it away |

## What to do

1. Wear a mask and gloves. Bag the mouldy buds where they sit so the spores don't spread.
2. Throw out every bud with fuzz, dust, a brown core or a musty smell, and every bud that touched one.
3. Open every jar. Break open the largest buds and check the cores.
4. Spread the clean buds on a screen at 15–21 °C (60–70 °F) and 55–62% RH until the small stems snap.
5. Re-jar them in clean jars, about ¾ full. Read the hygrometer only after 12–24 hours sealed.
6. Wash the old jars with hot soapy water and dry them fully.

## Common mistakes

- Trimming off the fuzzy bit and keeping the bud.
- Jarring buds by feel, without a sealed hygrometer test.
- Packing jars tight.
- Leaving a jar unopened for weeks early in the cure.

## Related

- Full article: [Botrytis (bud rot / grey mould)](https://genetixbay.com/knowledge/diseases/botrytis-bud-rot.md)
- Answers: [ammonia smell in jars](https://genetixbay.com/knowledge/answers/ammonia-smell-in-jars.md) · [how full to fill jars](https://genetixbay.com/knowledge/answers/how-full-to-fill-curing-jars.md)
- Articles: [curing and burping](https://genetixbay.com/knowledge/harvest-cure/curing-burping.md) · [drying](https://genetixbay.com/knowledge/harvest-cure/drying.md)
- Terms: [botrytis](https://genetixbay.com/knowledge/glossary/botrytis.md) · [water activity](https://genetixbay.com/knowledge/glossary/water-activity.md) · [mycotoxins](https://genetixbay.com/knowledge/glossary/mycotoxins.md)

## Follow-up questions

**Can I cut the mould off and keep the rest of the bud?** You cannot safely cut mould off a bud and keep the rest. Bud rot works from the inside, so the visible fuzz is the end of the infection, not its edge, and the spores spread through the jar. Discard the whole bud and any bud that touched it. Break open the biggest remaining buds and check for a clean core.

**Why did my buds go mouldy in the jar?** Buds go mouldy in a jar because they were jarred too wet or packed too tight. A sealed jar traps the moisture still in the bud cores, and above water activity 0.65 mould can grow. A jar that spikes to 75% RH or more overnight went in too wet. Wet, dense colas from a humid late flower can also carry botrytis in already.

**Are the other buds in the jar safe?** The other buds in a mouldy jar are only safe if they show no fuzz, no grey dust, no brown core and no musty smell when broken open. Spores will have spread in the jar air, so dry those buds out on a screen, re-check them, and put them in clean jars. When in doubt, throw it out, especially for anyone with a weak immune system.

## Sources

1. Punja ZK, Collyer D, Scott C, et al., 2019. Pathogens and molds affecting production and quality of Cannabis sativa L. Frontiers in Plant Science 10:1120. https://www.frontiersin.org/articles/10.3389/fpls.2019.01120/full
2. ASTM D8197. Standard Specification for Maintaining Acceptable Water Activity (aw) Range (0.55 to 0.65) for Dry Cannabis Flower. ASTM International. https://store.astm.org/d8197-22.html
3. ASTM International, Standardization News. Two cannabis standards you should know about (D8196 water activity measurement; D8197 range). https://sn.astm.org/node/2445/printable/print
4. PNW Plant Disease Management Handbook. Hemp (Cannabis sativa) - Gray Mold (Botrytis Bud Blight and Stem Canker). https://pnwhandbooks.org/plantdisease/host-disease/hemp-cannabis-sativa-gray-mold-botrytis-bud-blight-stem-canker