Short answer. Harvest when a 60x loupe shows the trichome heads on the buds as a few clear, mostly cloudy and some amber. That mix is a matter of preference: earlier and cloudier for a brighter finish, later with more amber if you like it heavier. Count from the flip and add the 10–14 day transition before trusting a breeder's week count. Keep feeding to the end, and skip the pre-harvest flush and the 24–72 h of darkness: both are Myths.
The founder, on knowing when she's ready: "Talk to her." She tells you more than you bargained for: swelling calyxes, pistils pulling in, the smell turning, the heads going milky. Look every other day in the last three weeks and you'll see it happen.
What do you need to judge harvest time?
You need a way to magnify trichomes and a record of dates; nothing else is essential.
- [ ] A 60x jeweller's loupe, or a clip-on phone macro lens or a small digital microscope (60–100x)
- [ ] A small torch or a white-light lamp (switch any coloured grow light to white or turn it off while looking)
- [ ] Your grow journal with the flip date and the date of first pistil clusters
- [ ] Clean, sharp pruning snips and gloves for harvest day
- [ ] A drying space ready at 15–21 °C (60–70 °F) and 55–62 % RH before you cut (drying step by step)
When should you start checking trichomes?
Start checking trichomes about two weeks before the earliest date your calendar suggests, then every two days. The calendar date is days since flip = breeder's flowering time + 10–14 days, because breeder times usually count from the first visible pistils, not from the switch to 12/12. In controlled studies first flowering came 8–14 days after short days began, and up to three weeks in slow cultivars [5]. See the photoperiod grow calendar and the flip-to-flower transition.
Autoflowers have no flip. Count days from germination and start checking at the earliest finish the listing gives, usually around day 63–70 (autoflower first grow).
How do you check trichomes, step by step?
Check trichomes the same way every time so the readings compare.
- Pick three sites: the top cola, a mid-canopy bud and a lower bud. The top usually ripens first.
- Light it with white light. Switch off a purple-tinted LED or use a torch.
- Look at the calyxes and bracts, not the sugar leaves. Leaf trichomes turn cloudy and amber earlier and fool you.
- Focus on the heads of the capitate-stalked trichomes, the mushroom-shaped ones.
- Estimate the mix in tenths: how many clear, cloudy and amber out of ten heads. Do it on two or three spots per bud.
- Write it down with the date and days since flip, for example "Day 68 since flip: 2 clear / 7 cloudy / 1 amber, top cola".
- Repeat every two days. The change from mostly clear to mostly cloudy usually takes 1–2 weeks; amber builds slowly after that.
- Cut when your target mix shows on the buds you care most about. If the lower buds lag by a week, you may harvest the tops first.
What trichome mix should you aim for?
Aim for a mix of a few clear, mostly cloudy and some amber; within that, it's your preference. That is the GenetixBay house position, and it matches the research: trichome heads go from clear to cloudy to amber or brown as they mature, browning marks gland senescence, and heads on one bract mature unevenly and at rates that differ by genotype [1][2]. Cannabinoid concentration typically rises to a plateau and then falls as the plant senesces [3].
| Mix on the buds | What it means | Typical choice |
|---|---|---|
| Mostly clear, few cloudy | Immature; cannabinoids still rising | Too early; wait |
| ~1–2 clear / 7–8 cloudy / 0–1 amber | Near the plateau | Earliest sensible harvest |
| ~1 clear / 7 cloudy / 2 amber | The classic mix | The default target |
| ~0 clear / 5–6 cloudy / 4–5 amber | Late; heads senescing | For growers who prefer it heavier |
| Mostly amber or brown, heads collapsing | Over-ripe | Losing quality; harvest now |
Treat this table as Grower practice. Genotype changes the pace, so log your cultivar's mix and date each run; that is how you learn its window (trichome ripeness).
Do amber trichomes mean a sleepier effect?
No, not in any proven way. The idea that amber heads mean high CBN and couch-lock is a Myth: CBN forms mainly by oxidation of THC after harvest, during storage [4], not on the living plant in any useful amount. Some growers report that later harvests feel heavier to them; that is a reported preference, and no controlled study shows a predictable effect from the amber share. Pick the mix you like and record it.
What other signs tell you she's nearly done?
Other signs back up the loupe but never replace it. Expect most of these in the last 2–3 weeks:
- Calyxes swell and stack; buds stop getting longer and get denser.
- Most pistils darken and curl in. Pistil colour varies by cultivar and stress, so it's only a hint.
- Lower fan leaves yellow slowly as the plant moves nitrogen to the flowers: normal senescence, not a reason to stop feeding.
- Water use drops a little; the smell gets stronger and changes.
Should you flush or use darkness before harvest?
No to both. Pre-harvest flushing is a Myth and actively harmful: it starves the plant in the weeks when it is packing on most of its final weight, trichomes and resin, and controlled studies found no quality gain [7]. Feed at stage strength to the end; if you mix single salts, taper only nitrogen. See the flush debate and feeding basics.
Darkness before harvest (24–72 h) is a Myth too, in the founder's words "complete and utter nonsense": why cut photosynthesis at the most critical part of the life cycle? Photosynthesis drives yield right to the end [6].
Greenleaf's standing challenge. For more than 20 years the founder has offered a 50-pack of seeds, no questions asked, to anyone who finds a peer-reviewed study (not a single-plant study, not biased or skewed) showing a benefit from darkness before harvest. Nobody has claimed it. See Mythbusters.
How will you know it's working?
You'll know your harvest timing is working when the logs line up run to run:
- Your loupe readings move from mostly clear to mostly cloudy over 1–2 weeks, then amber appears.
- The harvest date lands about 10–14 days past the breeder's stated time, counted from the flip, and you saw it coming.
- Dried buds are dense, smell strong and taste clean after the cure.
- Next run of the same cultivar, you can predict the window within a few days from your journal.
What mistakes do beginners make at harvest?
Beginners mostly harvest too early, or ruin a good harvest with a ritual.
- Harvesting by the breeder's week count from the flip, forgetting the 10–14 day transition.
- Reading sugar-leaf trichomes, which amber early.
- Judging by pistil colour alone.
- Flushing the last 1–2 weeks, which costs yield and resin.
- 48–72 h of darkness, which costs photosynthesis and gains nothing.
- Checking only the top cola when the lower buds are a week behind.
- Ignoring bud rot in dense colas in the final weeks: squeeze-check big colas and look for grey or brown inside (botrytis).
- Cutting with no drying space ready.
Evidence
- Trichome maturation clear → cloudy → amber, uneven and genotype-dependent: Supported [1][2].
- Cannabinoids rise to a plateau then decline: Supported [3].
- Amber = CBN = couch-lock: Myth; CBN forms mainly post-harvest [4].
- The 10–14 day transition after the flip: Supported [5]; house position.
- Darkness before harvest: Myth (house; no supporting study found) [6].
- Pre-harvest flushing: Myth [7].
- The trichome mix target: Grower practice, house position (preference).
