Harvest, dry, trim and cure
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Post-harvest · Process

Harvest, dry, trim and cure

This paper covers every post-harvest step from cut plant to sealed, finished flower: when to harvest, how to dry without losing terpenes or inviting mould, how to trim without damaging trichomes, and how to cure to a stable water activity. After reading, you will have target numbers at each step and a method you can repeat.

Post-harvest9 figuresEvidence-linked · 4 sources~14 min read
In this guide
01 Purpose and scope02 Definitions03 Evidence and limitations04 Harvest timing05 Harvest method and wet-plant weighing06 Drying environment07 Water activity08 Trimming and trichome protection09 Curing and storage10 Troubleshooting11 Expected results and limitations12 References
Start here

Purpose and scope

Post-harvest is everything that happens after the plant is cut down: drying, trimming, curing and storage. Weeks of careful growing can be ruined in a few days here. Dry too fast or too dry and you lose smell and weight. Dry too slow or too wet and mould takes hold.

Aim for a narrow safe zone: dry enough that mould cannot grow, but not so dry that the smell and weight evaporate away. Done well, dialling in this stage recovers sellable mass you would lose to bone-dry flower. Vendor figures of ~5-10% to final yield, because most growers are accidentally over-drying and losing sellable weight.[8]

The post-harvest pipeline, start to finish1Harvestcut plants atmaturity→2Hang dry60F / 60% RH,10-14 days→3Takedownsection at0.60-0.62 aw→4Trimremove leaf,save trichomes→5Cure & burpsettle to0.58-0.60 aw→6Seal & storestop burping,finishedEach step has a target number. Drying aims for the room, curing aims for the flower.
Figure 1. The five steps that turn a living plant into a finished, stable product. The numbers on each box are what you steer toward, explained section by section below.
Who this is for

Anyone harvesting their first crop who wants results they can repeat. This guide assumes zero prior knowledge and defines every term as it appears. It pairs with the mould-risk and airflow-design papers.

Vocabulary

Definitions

Two ideas do most of the work here. Don't memorise them. Each one comes back in context.

Water activity (aw)How ‘available’ the water in the flower is, on a 0 to 1.00 scale. It is the single best predictor of whether mould will grow. When the flower and the air around it reach balance, the air's relative humidity equals water activity times 100.[6]
Moisture content (%)The share of the flower's total weight that is water. This tells you about yield, not safety. It is a different number from water activity.
Relative humidity (RH)How much water vapour is in the air, from 0 to 100%. The dry-room target is 60% RH.
TrichomesThe frosty resin glands on the flower that hold the THC, terpenes and flavonoids. Protect these at every step. Handling knocks them off.
TerpenesThe aromatic oils that give each strain its smell and flavour. They evaporate if the flower gets too dry.
BurpingBriefly opening a sealed container during curing to let humid air out and fresh air in.
Two numbers that sound alike but do different jobs1Water activity0-1.00 scale ·predicts MOULD ·controls theprocess→2Moisture content% of weight ·predicts YIELD ·measures theproductWater activity tells you when it is safe and done. Moisture content tells you how much you have.
Figure 2. Water activity is the gauge you steer by. Moisture content is the gauge you report. Confusing the two is the most common beginner mistake.[8]
Burping walks jar humidity down to targetOpen the jars daily early in the cure to release moisture; ease off once they hold the target band on their own.target 58-62%5056616672seald1d2d3d4d5d6jar RH %
Diagram. Burping releases moisture early in the cure until the jars hold the target humidity on their own.
Evidence assessment

Evidence and limitations

How sure is this paper?

We've gone to great lengths to keep these guides honest. One of the main ways we do that is self-review: we actively look for claims that are subjective, only lightly backed by literature, or based on grower practice rather than a controlled study — and we call those out instead of dressing them up as settled science.

Often there simply is no paper for the decision you're making. In those cases we're drawing on what other growers report and what has worked in our own rooms. That can still be useful — but it is not a lab proof. Do what works for your plants, your room, and your meters. If a table disagrees with your crop, believe the crop and log the difference.

Solid
Well supported by plant science, standards, or broad multi-source consensus
  • Water activity predicts microbial risk better than moisture % alone (ASTM-style 0.55–0.65 for flower)
  • Slow cool dark dry protects terpenes better than hot fast dry
  • Light and heat accelerate cannabinoid/terpene degradation in storage
Operational
What many growers and rooms actually run — start here, then tune
  • 60 °F / 60% RH style hang-dry defaults and whole-plant hang practice
  • Dry-trim preference for many quality-focused rooms
Grain of salt
Subjective, thin literature, single studies, or “this works for us” practice
  • Vendor '5–10% yield recovered' figures as multi-site peer results
  • Exact aw drop from trimming as a universal constant

See something glaringly wrong? Tell us and we'll fix it. Please open a GitHub issue with the paper name and what looks off (include a source if you have one): Report an accuracy issue. Local law, labels, and licences always override any recipe here. Inline notes labelled grain of salt flag the highest-risk over-trust points in the text.

Step 1 of the science

Harvest timing

Harvest is cutting the plants down once they have finished flowering. Judge maturity by the flower itself, not by a date on the calendar.

The clearest signal is the trichomes. Under a loupe they shift from clear, to milky-cloudy, to amber as the plant ripens, and that colour change tracks how mature the resin glands are.[1] A typical workflow runs plants on a set flowering timeline with plant-work phases at days 7-10, 21-28 and 42-49, then cuts at the end.

  • Harvest = cutting down all plants once flowering is complete
  • Cut one strain at a time, in the order on your strain list, so genetics never get mixed
  • Keep each plant's tracking tag attached as it is cut. This is how batches stay traceable
  • Collect loose buds that fall on the table (‘table nugs’) per strain, label them, and dry them separately
Harvest is the end of a defined flowering cycleEach milestone is a scheduled task. Harvest is the last one.01346trellis d1lollipop d7-10defan d21-28final defan d42-49harvestplant-work stage
Figure 3. Harvest is the planned end of a sequence of plant-work milestones across the flowering room.
Let the plant decide

If the calendar says cut but the trichomes are still mostly clear, wait. Read maturity off the flower. The date is only a rough guide.

Step 2, hands on

Harvest method and wet-plant weighing

Cut plants whole and hang them to dry, rather than stripping the buds first. Cutters free each plant from the lower two layers of trellis netting (the support grid the plant grew through), leave the top layer on for support, then cut the main stalk at its base.

Before anything is hung, weigh every bin to record the wet weight, the starting weight. Compared against the final dry weight later, this gives the dry-to-wet ratio for each genetic, which is around 10% of whole-plant wet weight (one example batch came in at 10.46%). That tells you how much of the harvested mass is water.

  1. 1
    Free the plant
    Cut a circle through the bottom and middle trellis layers. Leave the top layer attached for support.
  2. 2
    Cut the stalk
    Sever the main stalk at its base so the whole plant comes away in one piece.
  3. 3
    Load the bin
    Place 7-10 whole plants per 208 L (55 gal) bin. Do not overfill or you bruise the flower.
  4. 4
    Weigh wet
    Tare the bin first, then weigh it to capture wet weight, the baseline for all yield tracking.
How much of a fresh plant is waterExample batch: dry weight was ~10.46% of wet weight. The rest left as water during drying.0295786115100%Wet weight10.46%Dry weight
Figure 4. Roughly nine-tenths of a freshly cut plant's weight is water that must leave during drying. Whole-plant hanging slows that loss and lets moisture move out of the stem evenly.
Water activity and moisture meters with dried buds
Example. Same bulk moisture reading can span dry-to-mouldy water activity. Steer post-harvest with aw (here ~0.61) not a cheap moisture % alone.Fact-check pack
The core science

Drying environment

Hold the dry room at 16 °C (60 °F) and 60% RH, with fans running and the lights off, in a room that was deep-cleaned before any plant went in. At these setpoints whole plants are typically ready in 10-14 days.[8]

Going slow and cool protects the terpenes, which evaporate in heat and dry air, and it stops the outside of the bud drying while the inside stays wet, the classic recipe for hidden mould. Keep the light off because it degrades cannabinoids and terpenes over time.[4] Different cultivars even reward slightly different drying approaches, so the setpoints are a strong default, not a law.[2]

  • Setpoints: 16 °C (60 °F), 60% RH, fans on, lights off, doors closed. Minimise foot traffic so the environment stays stable
  • Whole-plant drying takes about 10-14 days at these setpoints
  • If the room runs above 60% RH and dehumidification is undersized, exhaust fans can pull humidity down
  • Keep racks evenly spaced so air reaches every plant and buds dry uniformly. A deep clean precedes every load
Dry-room humidity should trend down toward takedownHold the room in the green band. The curve drifts down as the load gives up water.target 60% RHtoo humid: mould risktoo dry: terpene loss5256606468day 0day 3day 5day 8day 11day 14room RH %
Figure 5. The green band is the 60% RH target. Drift above it and you invite mould. Sit below it for long and terpenes start to evaporate.[8]
The core science

Water activity

After the hang-dry, the flower still contains some moisture—but not all moisture is equally dangerous. Think of a squeezed sponge sitting in a closed drawer: the water trapped deep in the fibres is harmless; the free surface water is what microbes actually feed on. Water activity (aw) measures how available that remaining moisture is to microbes, on a 0 to 1.00 scale. Mould and yeast can grow at 0.70 aw and above, pathogenic bacteria at 0.85, and risk rises sharply near that threshold; below ~0.55 aw, quality often suffers even as microbes slow. ASTM’s 0.55–0.65 window is the practical target for dried flower.[7] That sets the ceiling. Quality sets the floor: below 0.55 aw the terpenes dry up and quality falls off.

Together that leaves a sweet spot of 0.55-0.65 aw, the exact range written into the ASTM D8197 standard for dry cannabis flower.[5] Start sample testing around day 7-8, and take plants down when the batch averages 0.60-0.62 aw, leaving a safety margin below the 0.65 mould line.

The water-activity safe zoneTake plants down inside the green band, around 0.60-0.62 aw, well clear of the 0.65 mould line.too drysweet spot 0.60-0.62 = take downmould & yeastbacteria0.50.70.9
Figure 6. Below 0.55 aw you lose terpenes. Above 0.65 aw you risk mould. 0.60-0.62 aw is where you take the batch down.[5]
Water activity thresholds for microbial growthTake-down target (0.62 aw) sits below every growth threshold. That gap is your safety margin.00011target0.6 awNo growth0.7 awMould & yeast0.85 awBacteria
Figure 7. Drop the batch below the 0.70 aw mould line, with the take-down target at 0.62 aw giving headroom.[7]
Why water activity beats a cheap moisture meter
  • Water activity is the better control number because it varies far less than cheap moisture readings.
  • In one example, measuring on water activity gave roughly 10x tighter yield precision (±1% down to ±0.12%).
  • Denser flowers tend to finish at a slightly lower aw than fluffy ones. Use the meter as a guide, but also trust your nose.
Water activity (aw): the mould lineaw is the free water microbes can use. Cure to ~0.55-0.65: stable and smokeable, below the mould line.dry / stablecured targetriskymould grows0.30.60.9
Diagram. Dry and cure to a water activity that is stable and smokeable but below where mould can grow.
Step 3, hands on

Trimming and trichome protection

Trimming removes leaf so the bud looks clean and presentable. There are two timings. Wet trim means trimming right after cutting, before drying. Dry trim means trimming after the hang-dry. Dry trimming slows the dry and is gentler on the aromatic oils, which is why many operations choose it for better terpene retention.[3]

Never touch the flower itself. Handling knocks off the trichomes that carry potency and smell, leaving buds looking shaved and dull. To dry-trim, take plants down, cut them into 20–30 cm (8–12 in) sections, remove the large fan leaves by hand, then scissor off the smaller sugar leaves, swapping scissors into 71% alcohol as resin builds up.

  • Buck = cut the finished buds off the stem. Do this into a sealed bag so the flower does not over-dry in open air
  • Never touch the flower. Handling damages trichomes
  • Remove fan leaves (large, few trichomes) by hand, then scissor off sugar leaves
  • Clean scissors in 71% alcohol when resin builds up
  • After dry-trim, re-check aw, handling and leaf removal can change the reading, so do not assume the hang-dry number still holds
Wet vs dry trim. This guide dry-trims for better terpene retention and a gentler dry.[3]
Wet trimDry trim (this guide)
WhenRight after cuttingAfter the 10-14 day hang-dry
Drying speedFaster, harsherSlower, gentler
Leaf removalEasier (leaf is soft)Leaf is brittle, more care needed
Terpene retentionLower (more handling, faster dry)Higher, the reason it is chosen
Handling riskMoreLess
The core science

Curing and storage

Curing lets the whole batch settle to one even water activity, and preserves terpenes that would otherwise break down in storage. Hold flower in containers at 16–18 °C (60–65 °F) and 58-62% RH. Read a humidity sensor, and burp any bin reading above about 60% RH: lid off for 5-10 minutes, then rotate the barrel and log the reading.

Once the trimmed flower sits at 0.58-0.60 aw, it is finished: seal it and stop burping. Further burping just evaporates terpenes (lost smell) and water (lost sellable weight). Curing also keeps cannabinoids more stable by keeping the product cool and dark, the same conditions that slow degradation during storage.[4]

The daily burp decision1Read sensorcheck binhumidity→2Above 60% RH?yes -> burp 5-10min→3Rotate & logturn barrel,recorddate/RH/bin→4At 0.58-0.60 aw?yes -> seal,stop burpingLoop daily until the flower holds 0.58-0.60 aw, then seal and store.
Figure 8. Burp while wet, rotate for even drying, log every time, and stop the moment the flower reaches 0.58-0.60 aw.
Over-burping costs you money

Every burp past the finish line evaporates terpenes and water weight you could have sold. When trimmed flower reaches 0.58-0.60 aw, seal it. Bags should be free of air but not compressed, and not stacked, to protect bud structure.

What goes wrong

Troubleshooting

Most post-harvest failures are variations on going too fast, too dry, or too crowded. Over-drying is the quiet killer. A cheap moisture meter with ±1% error can read ‘11% moisture’ while the flower is anywhere from 0.53 aw (ruined, too dry) to 0.66 aw (mould risk), so growers chasing a single number often dry too far and lose weight and smell.[5]

What a single '11% moisture' reading actually hidesA +/-1% moisture meter spans 0.53 (too dry) to 0.66 (mould). A water-activity reading pins it to a 0.617-0.623 band.000110.53 awCheap meter low0.66 awCheap meter high0.617 awaw reading low0.623 awaw reading high
Figure 9. The same ‘11% moisture’ number can mean anything from ruined-too-dry to mould-risk. Water activity closes that gap to a fraction of a point.[5]
The big six post-harvest mistakes and their fixes.
MistakeWhat happensFix
Over-drying below 0.55 awTerpenes evaporate, smell fades, water weight lostTake down at 0.60-0.62 aw, stop curing at 0.58-0.60 aw
Drying too hot / fastOutside dries while inside stays wet, trapping mouldHold 16 °C (60 °F) / 60% RH and let it take 10-14 days
Trusting a cheap moisture meter±1% spans 0.53-0.66 aw, too dry to mouldyUse water-activity testing to decide done
Overfilling containersCrushed buds, trapped moistureFill totes/barrels no more than ~2/3, curing barrels no more than half
Touching the flower / skipping the deep cleanKnocked-off trichomes, contaminationHandle by stem only, deep-clean before every load
Safe aw but still smells wetInside not finishedLet it dry more. Your senses are the final check
Reality check

Expected results and limitations

Expect roughly 10-14 days of hang-drying plus several more days of curing before flower is truly finished. The whole post-harvest stage is two-to-three weeks, not overnight, and there is no rushing it.

The post-harvest finish line, day by dayTesting starts ~day 7-8. Takedown ~day 10-14 at 0.60-0.62 aw. Cure settles to 0.58-0.60 aw, then seal.safe zone 0.55-0.65 aw01111harvest d0test d7-8takedown d10-14trim & curesealedaw
Figure 10. A realistic arc: water activity falls from harvest, enters the safe zone at takedown, and settles in curing before the batch is sealed.[5]
Three rules
  1. It takes weeks, not days. Plan two-to-three weeks for the whole post-harvest stage and do not rush the dry.
  2. Stop over-drying. Dialling in drying and curing recovers sellable weight you would otherwise lose. The ~5-10% figures vendors quote are illustrative.[8]
  3. Genetics matter. Drying and curing are strain-dependent. Dense and fluffy flowers finish at slightly different aw points, so log every batch.[2]

Record the aw, RH, dates and outcomes for every genetic so good results are repeatable. The instrument is a guide, not a boss: inside the safe aw zone, trust smell and feel for the final call. When you are ready, read the mould-risk guide for what to do if a batch slips above the line, and the nutrient-mixing guide for the feed side of quality.

Related papers
Mould risk
Spot and stop bud rot
Airflow design
Move air like the pros
Mixing nutrients
Salts, in metric, done right

References

  1. Punja, Z.K., Sutton, D.B., & Kim, T. (2023). Glandular trichome development, morphology, and maturation are influenced by plant age and genotype in high THC-containing cannabis (Cannabis sativa L.) inflorescences. Journal of Cannabis Research, 5(1), 12. https://doi.org/10.1186/s42238-023-00178-9 https://doi.org/10.1186/s42238-023-00178-9
  2. Birenboim, M., Brikenstein, N., Duanis-Assaf, D., Maurer, D., Chalupowicz, D., Kenigsbuch, D., & Shimshoni, J.A. (2024). In Pursuit of Optimal Quality: Cultivar-Specific Drying Approaches for Medicinal Cannabis. Plants (Basel), 13(7), 1049. https://doi.org/10.3390/plants13071049 https://doi.org/10.3390/plants13071049
  3. Brikenstein, N., Birenboim, M., Kenigsbuch, D., & Shimshoni, J.A. (2024). Optimization of Trimming Techniques for Enhancing Cannabinoid and Terpene Content in Medical Cannabis Inflorescences. Medical Cannabis and Cannabinoids, 7(1), 111-118. https://doi.org/10.1159/000539192 https://doi.org/10.1159/000539192
  4. Fairbairn, J.W., Liebmann, J.A., & Rowan, M.G. (1976). The stability of cannabis and its preparations on storage. Journal of Pharmacy and Pharmacology, 28(1), 1-7. https://doi.org/10.1111/j.2042-7158.1976.tb04014.x https://doi.org/10.1111/j.2042-7158.1976.tb04014.x
  5. ASTM International. (2021). ASTM D8197-21: Standard Specification for Maintaining Acceptable Water Activity (aw) Range (0.55 to 0.65) for Dry Cannabis Flower Intended for Human/Animal Use. West Conshohocken, PA: ASTM International. https://www.astm.org/d8197-21.html (industry/manufacturer or non-journal source) https://www.astm.org/d8197-21.html
  6. U.S. Food and Drug Administration. Inspection Technical Guides: Water Activity (aw) in Foods. Office of Regulatory Affairs, FDA. https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/inspection-technical-guides/water-activity-aw-foods (industry/manufacturer or non-journal source) https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/inspection-technical-guides/water-activity-aw-foods
  7. AQUALAB (Addium, Inc.). How Water Activity Controls Microbial Growth. AQUALAB Learning Center. https://aqualab.com/learn/how-water-activity-controls-microbial-growth (industry/manufacturer or non-journal source) https://aqualab.com/learn/how-water-activity-controls-microbial-growth
  8. AROYA (Addium, Inc.). Processor's Guide to Moisture and Water Activity (Drying Cannabis). AROYA Education Guides. https://aroya.io/education-guides/drying-cannabis (industry/manufacturer or non-journal source) https://aroya.io/education-guides/drying-cannabis

Citations marked in-text as [n] map to this list. Primary literature and official guidance except where noted. Cannabis tissue culture is strongly genotype-dependent, verify dilutions, hormone doses and local regulations against the primary sources before relying on them.