How do I know my flower is dry enough?

The short answer

Flower is dry when its moisture content is right, not when a calendar says so. The published target for smokable flower is 8–13% moisture by weight, which puts it under the 0.65 water-activity line that several state regulators (Colorado, Washington, California) treat as the safety threshold — water activity being how much of the water left in the bud is still loose enough for mould and bacteria to use. Hang-drying typically takes 5–7 days to get there — but “typically” is doing real work in that sentence. Bigger, denser buds take longer; a dry room running at the wet or cold end of its band takes longer. The days are an estimate. The moisture is the endpoint.

Why the target is a range, and what sits at each edge

The number food scientists actually care about is that water-activity figure (aW) rather than the moisture percentage, because it is the part of the water that is loose enough for microbes to use. In cannabis the two line up at roughly 14% moisture to 0.65 aW, which is why the smokable-flower target stops just under it. Below about 0.6 aW, nothing much can grow at all — that’s the spoilage-safety edge of the range. The chapter is equally frank about the other direction: drying too fast or too far costs quality, which is why it doesn’t just say “drier is safer, keep going.”

Labs measure aW directly, but the meters run four figures, so at home you are estimating — by weight loss, by feel, by the usual stem-snap folklore. That’s fine as long as you know that’s what you’re doing: estimating a measured quantity, not counting down a timer.

The dry-room conditions with actual published backing

The same chapter gives the dry room itself concrete numbers: air temperature 18–21 °C (about 64–70 °F), relative humidity 45–60%, darkness throughout, and generous air exchange. Those are the bands I’d hold a dry space to, and they are cooler and wetter than a lot of grow-room folklore suggests — the point of a slow dry is to be slow.

And here is the honest caveat, which comes from the chapter itself rather than from me: even the field’s reference text says the optimal drying setpoints have yet to be established experimentally. The bands above are the best published guidance that exists, offered by authors who are candid that they’re describing good practice, not a solved problem. When a source admits the limit of its own evidence, I’d trust it more, not less.

What about curing?

Here the published record gets genuinely strange: there are no peer-reviewed publications on cannabis curing. None. That sentence comes from the field’s own textbook, not from a skeptic. Every confident claim you have read about what two weeks in a jar does chemically — whatever its merits — is practitioner knowledge, not measured science. Curing may well matter; growers with decades of experience insist it does. But nobody can currently tell you, with data, how long is long enough or what exactly is happening in the jar. Which means any app or device selling you a precise “days until cured” countdown is putting a decimal point on folklore.

Where my device fits, stated narrowly

Croplock treats the dry space as its own room with its own targets — the published bands above, held cool, wet-ish and dark — and where you’ve handed it equipment, it holds the room there and records what it did. What it deliberately does not do is show you a “days until jars” countdown, for the reason this whole page exists: the endpoint is a measured state of the flower, and the call is yours to make.

Sources

• Caplan, D., Matzneller, P. & Gutierrez, C. “Harvest and Post-Harvest.” Ch. 10 in Handbook of Cannabis Production in Controlled Environments (Y. Zheng, ed.), CRC Press, 2022. DOI 10.1201/9781003150442. Moisture and water-activity targets, dry-room bands, typical durations, and both candour statements (setpoints not established; no peer-reviewed curing literature) are from §10.7.
• Grant, C. et al. (2004), on water activity and microbial growth limits, as cited in the chapter above.

More of these at Answers. The device is at croplock.com.