Flowering is eight to ten weeks of visible, week-by-week change, and knowing what each week is supposed to look like is the difference between harvesting at peak and guessing. This guide walks the full timeline: what you will see, what you will smell, what can go wrong in that specific week, and exactly how to read trichomes when the finish line arrives.
- The timeline at a glance
- Weeks 1 to 3: the stretch
- Weeks 3 to 4: buds set
- Weeks 4 to 6: bulk
- Weeks 6 to 8: ripening
- Week 9 and beyond
- Trichomes: the real harvest signal
- Harvest window checker
- Problems by week
- Environment targets through flower
- Light and feeding through the stages
- Autoflower timing
- Frequently asked questions
- The short version
The timeline at a glance
Photoperiod plants start flowering when the light schedule flips to 12 hours on, 12 hours off. Week 1 begins at the flip. Most modern hybrids finish in 8 to 9 weeks; sativa-leaning strains can run 10 or more.
| Week | Stage | What you see | Your job |
|---|---|---|---|
| 1 | Transition | Rapid vertical growth begins, no visible buds yet | Support the stretch, keep training |
| 2 | Transition | First pistils: white hairs at branch tips and nodes | Confirm sex, remove any males |
| 3 | Early flower | Stretch slows; tiny bud sites form up each cola | Final defoliation window |
| 4 | Bud set | Real buds, white pistils everywhere, first frost | Full flowering feed, start watching humidity |
| 5 | Bulk | Buds thicken daily, smell arrives properly | Carbon filter on, humidity below 55 percent |
| 6 | Bulk | Colas begin to close up, trichomes coat sugar leaves | Inspect dense buds, keep air moving |
| 7 | Ripening | Pistils start turning orange, growth slows | Start checking trichomes with a loupe |
| 8 | Ripening | Buds firm, most pistils darkened, trichomes cloudy | Harvest window opens for many strains |
| 9 to 10 | Finish | Amber trichomes appear, fan leaves may yellow | Harvest at your chosen trichome mix |
Weeks 1 to 3: the stretch TRANSITION
Week 1: the flip
What you see: nothing flowery yet, and that is normal. The plant reads the longer dark period as autumn and shifts hormones, but outwardly it just grows, fast. Internode spacing opens up and the whole plant reaches.
What to do: keep light leaks out of the dark period (even a small leak can cause reveg or herms), keep training pliable new growth, and plan for height. A plant that fills half your tent at flip will fill all of it by week 3.
Week 2: first pistils
What you see: pairs of fine white hairs at branch tips and upper nodes. Those are pistils, and they confirm a female. Males instead show small round pollen sacs like tiny bunches of grapes, with no hairs.
What to do: sex every plant this week and remove males immediately if you grew from regular seed. One open pollen sac can seed a whole room. Growing from clones skips this entire risk, since every clone is a cut of a known female.
Week 3: stretch ends
What you see: vertical growth slows to a stop. Most strains finish 50 to 100 percent taller than at flip; sativa leaners can double and more. Tiny bud sites, like little tufts, dot the length of each cola.
What to do: this is the last sensible defoliation window. Clearing interior leaf now improves light and airflow into the middle of the plant for the whole bulk phase, and the plant has time to recover before it needs every leaf working.
Weeks 3 to 4: buds set EARLY FLOWER
Week 4: real buds
What you see: bud sites merge into recognizable small buds, still mostly white pistils. The first trichomes appear as a light sparkle on the small leaves around the buds. Smell starts, politely for now.
What to do: the plant's appetite peaks over the next month. Feed a full flowering profile, and start treating humidity as a flowering input: under 55 percent from here, heading lower later. This is also the week to hang the carbon filter if it was not already in line, before the smell stops being polite. Our ventilation guide covers the airflow side of late flower.
Weeks 4 to 6: bulk PEAK GROWTH
Week 5: buds thicken daily
What you see: visible day-over-day growth. Buds swell, colas begin to look like colas, trichome coverage spreads from bud leaf to the flowers themselves. Smell is now a fact of the household.
What to do: water demand jumps with the growth. Keep nights within about 10°F (5°C) of days to avoid stressing the plant, and keep air moving through the canopy, not just around it.
Week 6: colas close up
What you see: individual buds along each cola grow into each other and the cola reads as one continuous flower. Density is building, which is the goal and also the risk: dense buds trap moisture.
What to do: begin the late-flower inspection habit: gently part your densest colas every few days and look inside for any gray fuzz or browning. Caught in week 6, bud rot costs you a bud. Caught in week 9, it costs colas.
Weeks 6 to 8: ripening RIPENING
Week 7: the turn
What you see: new pistil production slows, and existing pistils start darkening from white to orange and curling inward. Bud growth continues but decelerates. Trichomes are dense enough that buds look dusted.
What to do: start trichome checks with a jeweler's loupe or USB microscope (30x to 60x). You are establishing a baseline: mostly clear now, so you can see the change week over week. Drop humidity to 45 to 50 percent.
Week 8: the window opens
What you see: buds feel firm when gently squeezed at the base. Most pistils have turned. Under the loupe, trichome heads have gone from clear glass to milky cloud on many strains. Some fan leaves begin to fade yellow, which is normal senescence, not a deficiency, this late.
What to do: if the breeder says 8 weeks and trichomes agree (cloudy, little amber), this is harvest. If trichomes are still heavily clear, believe the trichomes, not the packaging. Many strains sold as 8-week finishers want 9.
Week 9 and beyond FINISH
Weeks 9 to 10: ripe, then past ripe
What you see: amber trichomes appearing and spreading, day by day. Pistils fully darkened and receded into swollen calyxes. Leaf fade accelerates. On long-flowering sativas, all of this simply happens later; week 9 for them can look like week 7 above.
What to do: harvest at your chosen trichome mix (next section). Waiting past roughly 30 percent amber trades potency character for heaviness, and eventually THC degrades toward CBN, which is more sedating and less potent. Buds do not improve by standing still.
Trichomes: the real harvest signal
Calendar weeks estimate; trichomes decide. A trichome is a tiny resin gland shaped like a golf ball on a tee, and its color tells you the chemistry inside:
| Trichome mix | Chemistry | Effect profile | Verdict |
|---|---|---|---|
| Mostly clear | THC still being synthesized | Light, racy, shorter lasting | Too early. Wait. |
| Cloudy, 0 to 10 percent amber | Peak THC | Strongest, most energetic expression | Harvest for potency |
| Cloudy with 20 to 30 percent amber | Peak THC with some CBN | Balanced, more body relaxation | The most popular window |
| Majority amber | Meaningful THC degradation | Heavy, sedative, couch-bound | Deliberate choice for sleep strains, late for everything else |
Check trichomes on the buds themselves, not the sugar leaves. Leaves mature ahead of flowers and will read amber while the buds are still cloudy. Check two or three spots per plant, since the top cola ripens ahead of shaded lower buds.
Harvest window checker
Loupe in hand, estimate your percentages on the flowers and let this call it:
Problems by week
Flowering problems cluster at predictable points. Here is where to look when a week goes sideways:
| Weeks | Common problem | What it looks like | First move |
|---|---|---|---|
| 1 to 3 | Uncontrolled stretch | Plants hit the light, foxtailing tops, burned crowns | Raise light, supercrop the tallest colas, accept some bend |
| 2 to 3 | Hermaphrodites | Pollen sacs among pistils, usually after light leaks or stress | Inspect with the room dark for leaks; remove affected plants |
| 4 to 6 | Nutrient burn | Scorched leaf tips marching inward during heaviest feeding | See our nutrient burn guide; ease off before flushing everything |
| 4 to 6 | Cal-mag hunger | Rust spots mid-canopy, yellowing between veins | Common under LED; see the cal-mag guide |
| 6 to 10 | Bud rot | Gray fuzz inside dense colas, single dead sugar leaves pulling out easily | Remove infected material immediately, drop humidity; full protocol in the bud rot guide |
| 7 to 10 | Panic over yellow fan leaves | Lower leaves fading and dropping | Late-flower fade is normal ripening; do not chase it with nitrogen |
Environment targets through flower
The plant's tolerance for heat and humidity shrinks as the buds densify. This table is the flowering environment in one place; the reasoning behind the numbers lives in the VPD guide and the ventilation guide.
| Weeks | Day temp | Humidity | VPD target | Why it changes |
|---|---|---|---|---|
| 1 to 3 | 75 to 82°F (24 to 28°C) | 55 to 65% | 1.0 to 1.2 kPa | Plant is still building leaf; treat it like late veg |
| 4 to 6 | 72 to 80°F (22 to 27°C) | 45 to 55% | 1.2 to 1.4 kPa | Buds are forming; mold risk begins with density |
| 7 to harvest | 68 to 78°F (20 to 26°C) | 40 to 50% | 1.3 to 1.5 kPa | Dense colas trap moisture; cooler nights deepen colors |
Two habits matter more than the exact numbers. First, hold the humidity line overnight: the dangerous spike happens after lights off, when temperature falls and relative humidity jumps. Second, change conditions gradually. A plant that lived at 65 percent humidity does not enjoy a same-day drop to 40; walk it down a few points at a time across the transition weeks.
Light and feeding through the stages
Flowering demand follows the same arc as the visual timeline: climbing into the bulk weeks, easing at the end.
- Weeks 1 to 3: the plant still wants a hybrid diet. Keep some nitrogen flowing through the stretch, because it is building the leaves that will feed every bud later. Light can step up toward flowering intensity: around 800 to 1,000 PPFD for a well-managed canopy, less if you cannot hold temperature and humidity in range.
- Weeks 4 to 6: peak appetite. Full flowering feed, phosphorus and potassium forward, with cal-mag support under LED. If a deficiency is going to appear, it appears now, and mid-canopy rust spots this month are cal-mag until proven otherwise.
- Weeks 7 to finish: demand tapers as the plant shifts from building to ripening. Chasing the late fade with more nitrogen keeps buds greener than they should be and harshens the smoke. Let the fade happen; it is the plant emptying its own pantry into the flowers.
Autoflower timing
Autoflowers run the same stages on their own internal clock, with no light flip. Count from sprout instead: flowering typically starts around week 4 to 5 of life, and the whole plant finishes at 10 to 12 weeks seed to harvest. The week-by-week signs above still apply, compressed; the trichome rules apply unchanged. What you cannot do with an auto is hold it in veg until it fits your schedule, which is why photoperiod clones remain the choice for growers who want control over plant size and timing.
Frequently asked questions
How long is the flowering stage?
Eight to nine weeks for most modern hybrids, seven to eight for fast indica leaners, and ten or more for strong sativas. Breeder estimates start at the light flip, not at the first pistil, and they tend to run one week optimistic.
What week do buds grow the most?
Weeks 4 through 6 are the bulk phase, when buds visibly gain mass daily. The final two weeks add density and resin more than size.
What should buds look like at week 5?
Distinct, thickening buds covered in mostly white pistils, with trichomes clearly visible on the surrounding small leaves. If your week 5 buds are still sparse tufts, the plant probably spent extra time transitioning: count a week later and reassess before changing anything.
When should I stop feeding nutrients?
Growers who flush typically switch to plain water for the final one to two weeks, timed off trichome checks rather than the calendar. Media matters: coco and hydro turn over faster than a heavily amended organic soil, which barely needs a flush at all.
Why are my pistils turning brown at week 4?
Scattered early browning is normal aging, especially after pistils get wet or touched. Widespread darkening this early with no bud swell can signal pollination: check for seeds forming in a calyx before assuming all is well.
Can I harvest the top of the plant and let the bottom keep ripening?
Yes. Staggered harvest works well: take the ripe top third, then give lower buds another five to ten days under the light they finally receive. It is the standard answer to plants that ripen unevenly.
Do bigger yields come from longer flowering?
Not directly; letting an 8-week strain sit for 10 weeks adds degradation, not weight. Yield is set by light, canopy management, and genetics. If harvest size is the goal, see how much one plant yields and start from high-yield genetics.
Every week of this timeline is easier with vigorous, verified genetics. Browse our rooted, HLVd-tested clones, or start with forgiving beginner strains for a first flowering run.
The short version
Flip to 12/12 and expect stretch through week 3, buds by week 4, daily swelling through week 6, and ripening signs from week 7. Confirm females in week 2, defoliate by week 3, get the carbon filter working by week 4, and treat humidity as a flowering input from week 5 on. From week 7, check trichomes on the buds with a loupe: harvest on cloudy for potency, cloudy with a quarter amber for balance. The calendar gets you close. The trichomes make the call.
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