During the cannabis flowering stage, your job is to hold a steady 12/12 light cycle, cut nitrogen and raise phosphorus and potassium, keep humidity near 40 to 50 percent with strong airflow, and stop all high-stress training once buds set. Support heavy colas, scout daily for bud rot and mites, and harvest based on trichome color instead of the calendar. Everything else, from defoliation to flushing, is a smaller adjustment layered on top of those five basics.
What happens during the cannabis flowering stage?
Flowering starts when the plant receives at least 12 hours of uninterrupted darkness each day, which flips it from vegetative growth to bud production. The first two to three weeks are the stretch, when stems can double in height. Bud sites then form and swell over roughly six to ten weeks, depending on the cultivar.
Cannabis Flowering Stage vs Vegetative Stage: A Comparison Review
What should you do in the first weeks of flowering?
- Switch to a 12/12 light schedule and seal every light leak, because even brief light exposure can delay or reverse flowering.
- Start bloom nutrients at roughly half strength and increase over two weeks.
- Install stakes, trellis netting, or yoyos before the colas pack on weight.
- Keep the canopy even by tucking tall stems rather than cutting them.
How do you feed cannabis during flowering?
Reduce nitrogen, which drives leafy growth, and increase phosphorus and potassium to support bud development. Most growers feed bloom formulas from week two through week six or seven, then taper. Watch leaf tips for tip burn and back off the strength if you see it.
Calcium and magnesium matter more in flowering, especially under LED lights or in coco. A calmag supplement at the label rate prevents the rusty spots and yellowing that show up mid-flower.
what to do during cannabis flowering stage
What light schedule and temperature does flowering cannabis need?
Keep lights at 12 hours on and 12 hours off for the entire flowering period, with no interruptions during the dark cycle. Daytime temperatures near 75 to 80 degrees Fahrenheit and nighttime temperatures 5 to 10 degrees cooler support steady development. Cooler nights can also encourage the purple and deep green coloration some cultivars express.
How do you control humidity and prevent bud rot?
Drop relative humidity to 40 to 50 percent once buds form, since dense colas trap moisture and invite botrytis. Run an oscillating fan across the canopy and an exhaust fan to move air out of the tent or room. In late flower, keep humidity closer to 40 percent and inspect the inside of large buds every day.
Should you defoliate or train plants during flowering?
Light defoliation of fan leaves that shade bud sites is useful around week three and again near week five. Avoid topping, supercropping, and heavy bending after week three, because recovery time eats into bud development. Stop all high-stress training once flowers set and let the plant finish.
When should you flush and harvest?
Trichome color is the most reliable harvest signal: clear means too early, cloudy means peak potency, and amber means more sedation. Many CBD-rich cultivars are harvested in the cloudy window, so check trichomes on the buds, not the sugar leaves. If you use bottled nutrients, flush with plain water for the final 7 to 14 days.
Common flowering mistakes to avoid
- Leaving light leaks that cause herming or stalled bud growth.
- Pushing nitrogen too long and getting airy, leafy flowers.
- Letting humidity climb above 60 percent with dense colas.
- Harvesting on a fixed day count instead of checking trichomes.
How often should you water during flowering?
Watering frequency usually increases because plants drink more as buds swell. Check the weight of the pot or the top inch of medium instead of following a fixed schedule. In late flower, many growers water slightly less to reduce humidity around the root zone.
Can you take clones during flowering?
Yes, but clones taken from a flowering plant must revert to vegetative growth first, which takes two to four weeks. Take cuttings in week one or two if you want to preserve a specific phenotype. After week three, revegetation slows down and success rates drop.