After weeks of vegging and growth, your cannabis plants are finally ready to flower. But flipping into flower isn’t just about changing the light schedule — it’s about giving your plants everything they need to make the switch successfully.
Table of Contents
- 1. When to Flip to Flower
- 2. Switching to 12/12 Lighting
- 3. Environmental Adjustments
- 4. Transitioning to Flower Nutrients
- 5. What to Expect After the Flip
1. When to Flip to Flower
There’s no perfect day to flip, but a good rule of thumb is once your plants have filled 50-75% of your grow space. Remember: plants will usually double in size during the first few weeks of flowering (called “the stretch”).
Flipping too early can reduce yields, while flipping too late can overcrowd your space.
2. Switching to 12/12 Lighting
To trigger flower, change your lighting schedule to 12 hours on / 12 hours off. This mimics nature’s shorter days and signals the plant to start flowering.
- Use a timer to maintain perfect 12/12 cycles
- Make sure your dark cycle is completely uninterrupted (no light leaks!)
- Lights off time should match your room temperature goals (nights are cooler)
Once you flip, it usually takes 7–14 days to see clear signs of flowers starting to form.
3. Environmental Adjustments
As your plant shifts from veg to flower, its needs change. The ideal flower environment differs from veg:
- Temperature: 70–80°F (lights on), 65–72°F (lights off)
- Humidity: Drop RH to 40–50% to avoid mold and mildew
- Airflow: Increase fan power and circulation
- Smell: Consider adding a carbon filter if odor is a concern
This stage is more sensitive to high humidity and poor airflow — take it seriously if you want dense, mold-free buds.
4. Transitioning to Flower Nutrients
Your plant needs a new diet. Flowering requires more phosphorus and potassium, and less nitrogen. That means:
- Switch to a bloom nutrient formula designed for your medium (soil, coco, hydro)
- Reduce nitrogen-heavy veg nutrients to prevent leafy buds
- Flush or rinse your medium if you’re making a major nutrient change
Pro Tip: Stick with one nutrient brand and follow their feeding schedule. Less is more — underfeeding is safer than overfeeding.
5. What to Expect After the Flip
The first 2–3 weeks after switching to 12/12 is called “the stretch” — your plants will grow rapidly and may double in height.
You’ll start to see:
- New bud sites forming at every node
- Increased water and nutrient uptake
- Height surge — adjust your lights often!
- Early white pistils showing on female plants
Be prepared to train your plants during this time using low stress training (LST) or a trellis net to control vertical growth and maximize yield.
Flipping to flower is one of the most exciting parts of the grow cycle. With the right timing, environment, and nutrients, you’re on the path to healthy blooms and potent buds. Treat this phase with care — the decisions you make now determine your harvest later.