Cannabis Flowering Stage: Week-by-Week Guide

The cannabis flowering stage is the reproductive phase that starts when a plant gets 12 hours of uninterrupted darkness each day and runs about 7 to 10 weeks indoors. The plant stops building height, forms bud sites at every node, and produces the cannabinoids and terpenes that decide potency and aroma. Flowering ends when trichomes turn cloudy with a few amber heads, which is harvest window.

Cannabis Flowering Time by Strain Guide

How long does the cannabis flowering stage last?

Most photoperiod strains finish in 8 to 10 weeks after the light flip. Indica-leaning plants often wrap up in 7 to 9 weeks, while sativa-leaning plants can run 10 to 14 weeks. Autoflowering plants skip the light flip and finish flowering in roughly 8 to 10 weeks from the first pre-flowers.

When to Switch to Flowering Cannabis: The Right Time to Flip

Breeder estimates are a starting point, not a schedule. Judge ripeness by the plant, not the calendar.

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What happens week by week during flowering?

Weeks 1 to 3: stretch and pre-flower

Vertical growth can double in this window, so keep the light canopy in mind before the flip. Small pistils appear at the nodes, and the plant shifts its demand toward phosphorus and potassium.

Weeks 4 to 6: bud development

Calyxes stack, pistils multiply, and resin production ramps up. This is the heaviest feeding stretch, when buds gain most of their final mass.

Weeks 7 to 10: ripening

Pistils darken and curl inward, bud swelling slows, and fan leaves fade. Trichomes mature from clear to cloudy as THC peaks.

How do you know when to harvest?

Check trichomes on the calyxes with a 30x to 60x magnifier, not on the sugar leaves, which mature early. Clear heads mean the plant is still building, cloudy heads mean peak THC, and amber heads mean THC is converting toward CBN and a heavier effect.

As a secondary check, most pistils should be orange and curled in before you consider cutting. A 24 to 48 hour dark period before harvest is optional, not required.

What does cannabis need during flowering?

• Light: a strict 12 hours on, 12 hours off, with no light leaks during the dark period.
• Nutrients: more phosphorus and potassium, less nitrogen, which slows stretch and leaf growth.
• Temperature: 68 to 78 F during lights on, and about 10 F cooler at night for terpene retention.
• Humidity: 40 to 50 percent in early flower, dropping to 40 to 45 percent late to reduce mold risk.
• Airflow: continuous gentle movement over and under the canopy.

Common flowering stage mistakes

• Harvesting too early, before trichomes cloud up.
• Overfeeding and causing nutrient burn during peak bud set.
• Letting humidity climb, which invites bud rot in dense colas.
• Interrupting the dark cycle with a tent zipper gap or a phone light.

Should you defoliate during flowering?

Light leaf removal in weeks 3 and 6 improves airflow and light penetration into lower bud sites. Strip too much and the plant stalls, so remove only leaves blocking bud sites or trapping moisture.

Does flushing before harvest matter?

Reducing nutrients in the final 7 to 14 days is common practice and can improve the taste of the finished flower. Plain water in the last stretch is enough, since the plant is already drawing stored reserves from fading leaves.