# Hay smell

> A grassy, hay-like aroma in dried cannabis caused by drying too fast, over-drying or bacterial activity; in GenetixBay's view it never fully cures out.

- Canonical: https://genetixbay.com/knowledge/glossary/hay-smell.html
- Also written: smells like hay, grassy smell, hay-like smell, smells like cut grass, green smell
- Glossary category: Harvest, drying and curing · Evidence: Grower practice
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

Hay smell is the flat, grassy or hay-like aroma of badly dried cannabis, often with a harsh, green taste on smoking. It replaces or masks the cultivar's normal [terpene profile](https://genetixbay.com/knowledge/glossary/terpene-profile.md). The usual causes are drying too fast (warm, [dry rooms](https://genetixbay.com/knowledge/glossary/drying-room.md) or [fans](https://genetixbay.com/knowledge/glossary/fan-leaf.md) blowing on buds), [over-drying](https://genetixbay.com/knowledge/glossary/over-drying.md), or bacterial and microbial activity in material that sat too wet, too warm, or packed too tightly.

## In practice

[Prevention](https://genetixbay.com/knowledge/glossary/cultural-control.md) is the cure:
- Dry slowly, about 7-14 days at around 15-21 °C (60-70 °F) and 55-62% [RH](https://genetixbay.com/knowledge/glossary/relative-humidity.md).
- Keep air moving around, not onto, the buds.
- Don't pack wet buds into bags or bins.
- Jar at the [stem snap](https://genetixbay.com/knowledge/glossary/stem-snap-test.md), then cure as a slow decline in moisture.

If a batch smells of hay, a long, careful cure may soften it a little, but it won't bring back what was lost.

## Don't confuse with

- **Ammonia smell**: wet material with microbial growth; check for mould.
- **Musty smell**: mould; inspect and discard affected buds.
- **Fresh "green" smell at chop**: normal before the dry.

## Myth check

House position: a cure will never fix a bad dry. Hay smell means bacteria, over-drying or drying too fast, and it never truly comes out. Nor does it come from "not [flushing](https://genetixbay.com/knowledge/glossary/flushing.md)": taste and ash come from drying, curing and plant health (Myth). See [the flush debate](https://genetixbay.com/knowledge/harvest-cure/flush-debate.md).

## Related terms

[Curing](https://genetixbay.com/knowledge/glossary/curing.md), [Drying room](https://genetixbay.com/knowledge/glossary/drying-room.md), [Over-drying](https://genetixbay.com/knowledge/glossary/over-drying.md), [Chlorophyll](https://genetixbay.com/knowledge/glossary/chlorophyll.md), [Terpene loss](https://genetixbay.com/knowledge/glossary/terpene-loss.md)

## Read more

- [Drying cannabis: the 60/60 method and water activity](https://genetixbay.com/knowledge/harvest-cure/drying.md)
- [Curing and burping: jars, humidity and how long](https://genetixbay.com/knowledge/harvest-cure/curing-burping.md)

## Sources

1. Ross SA, ElSohly MA. 1996. The volatile oil composition of fresh and air-dried buds of Cannabis sativa. Journal of Natural Products 59(1):49-51.
2. University of Georgia (thesis). Effects of drying method and storage on cannabinoids and terpenes in hemp. https://openscholar.uga.edu/record/27813