Cannabis flowering runs 7 to 10 weeks for most photoperiod strains, and autoflowers finish 8 to 11 weeks from seed. The harvest date comes from trichome color, not the calendar: cloudy heads with a few amber means ripe. Breeder week counts set expectations, and a close look at the resin sets the day.
How long does cannabis take to flower?
Photoperiod plants start flowering when you cut light to 12 hours a day. Count from the first 12/12 day, not from the day buds show.
- Indica-leaning strains: 7 to 9 weeks.
- Hybrids: 8 to 10 weeks.
- Sativa-leaning strains: 10 to 12 weeks, sometimes 14.
- Autoflowers: 8 to 11 weeks from seed, with 6 to 8 of those in flower.
Add 1 to 2 weeks of pre-flower stretch before real buds form. Total time from light flip to chop lands near 10 to 12 weeks for most photos.
What are the stages of cannabis flowering?
Weeks 1 and 2: Transition and stretch
Stems lengthen, nodes space out, and the plant stops making new leaf pairs. Small pre-flowers appear at the node joints. This stretch can add 50% to plant height, so plan your light height now.
Weeks 3 and 4: Early flower
White pistils push out of the calyxes and bud sites stack into clusters. The plant needs steady light and an unbroken dark period. A light leak at this point can stall a crop or send it back into veg.
Weeks 5 and 6: Bulk
Buds fill in and put on most of their weight. Water use climbs, and so does the pull on phosphorus and potassium. Tie up weak branches before they tip under their own load.
Weeks 7 and 8: Swell and fade
Calyxes swell, pistils shift from white to orange, and older fan leaves yellow as the plant moves nutrients into the buds. Resin peaks in this window on fast strains. This is the first week worth checking trichomes.
Week 9 and beyond: Ripening
Sativa-leaning plants keep throwing fresh white pistils while older ones brown off. Wait for that last push of new pistils to stop before you judge ripeness. A plant that still grows new hairs is still working.
How do you tell when to harvest?
Trichomes on the calyxes, not the sugar leaves, are the signal that counts. Pistil color and breeder week counts are rough guides at best.
- Check trichome heads under 30x to 60x magnification, on bud sites at mid-plant height.
- Clear or glassy heads: early, with a thin effect and less weight.
- All cloudy, milky heads: the peak THC window for most growers.
- Cloudy with 10 to 20% amber: more body, a small drop in THC.
- Almost all amber: past peak, save it for sleep or pain use.
Other signs to read alongside the resin: buds stop swelling, water uptake drops, and the smell settles from sharp to round. Use those as a second opinion, never as the only one.
What moves harvest time earlier or later?
- Genetics: the biggest factor. Two plants from one pack can finish a week apart.
- Light intensity: strong light on healthy plants can pull a finish a few days earlier.
- Temperature: cool nights slow ripening, and heat pushes foxtails and delays.
- Root space: small pots speed senescence, while large pots stretch it out.
- Stress: drought or nutrient swings can force an early finish with less weight.
Is convenience now the deciding factor in harvest timing?
Autoflower seeds, fast-finishing cultivars, and cheap trichome scopes turned the schedule from guesswork into a plan. A grower can pick a strain by its finish window and book a dry room before the seed even sprouts. That is convenience doing real work.
What convenience cannot do is set the date. A plant sold as an 8-week strain that still throws white pistils at week 9 needs more time. The week number starts the check, and the trichomes end it.
The trade-off shows up in yield. Fast strains and tight schedules save space and time, yet a plant cut a week early can lose 10 to 20% of its final weight. Convenience wins when it removes labor, not when it shortens ripening.
What should be ready before harvest day?
- A scope or loupe, charged and within reach.
- Clean pruning shears, wiped with alcohol.
- A dark, ventilated dry space at 60 to 70F and 45 to 55% humidity.
- Gloves and a trim tray, so wet trimming does not become a scramble.
Set all of it up in week 7, not on chop day. Most harvest mistakes come from rushing, and prep is the cheapest fix.
Frequently asked questions
Can you harvest too early?
Yes. Early harvest gives less weight, a sharper smell, and a shorter high. Cutting a week ahead can cost 10 to 20% of yield on a plant that had more to give.
Do autoflowers follow the same flowering stages?
Yes, just on a tighter clock. They flip to flower on their own around week 3 or 4 and follow the same stretch, bulk, and swell pattern.
How long from light flip to harvest?
Most photoperiod grows take 9 to 11 weeks from 12/12 to chop. Add a week or two for slow sativas, and start checking trichomes at week 7.