Growing cannabis outdoors has its rewards, but timing can be tricky. Whether you’re dealing with a short season, cold nights, or urban light pollution, sometimes nature’s schedule just doesn’t cut it. That’s where forced flowering comes in. This guide explains why and how to trigger the flowering stage early, so you can protect your harvest and potentially even squeeze in an extra crop.
Why Force Cannabis to Flower Early?
Letting outdoor cannabis plants flower naturally works well in some regions, but in others, it’s a gamble. In colder areas, waiting for nature to take its course often leads to mold, rot, or frost damage. In warm climates, flipping plants early can result in two or even three smaller harvests per year. In cities, artificial light can delay or even prevent flowering altogether.
By taking control of the light cycle, you can:
- Avoid damage from fall weather
- Harvest earlier in short-season regions
- Schedule multiple harvests in milder climates
- Offset the effects of light pollution in urban areas
Climate-Specific Flowering Strategies
Cold and Northern Climates
In places with chilly autumns, such as northern Europe or inland valleys, plants left to flower naturally often face frost before they have a chance to finish blooming. Growers in these zones typically start their plants indoors in late winter and then move them outside once the temperatures rise. Then, by early summer, they begin light deprivation techniques to kick-start flowering and beat the cold.
Mild and Warm Regions
If you’re lucky enough to grow in areas with long summers and gentle winters, forced flowering can help you fit in multiple harvests a year. Smaller plants are grown and flipped in batches, allowing a rotating schedule of bud-ready crops. The plants might not get huge, but you get a consistent supply and better control.
How to Force Outdoor Plants to Flower
Control the Light Schedule
Cannabis starts flowering when days shorten to around 12 hours of light and 12 hours of darkness. Outdoors, that natural shift doesn’t happen until late summer, but you can simulate it earlier. Once your plants are large enough, start covering them every day to provide them with 12 full hours of complete darkness.
Use Blackout Covers or Light-Deprivation Structures
You’ll need materials that block all outside light. Some options include:
- Thick blackout tarps or tents
- Heavy-duty curtains
- DIY structures like greenhouse frames wrapped in black plastic
Make sure your setup is:
- Fully sealed, no gaps or pinholes for light to sneak in
- Easy to uncover each morning
- Well-ventilated to prevent humidity buildup
Keep the Schedule Consistent
Consistency is everything. Cover your plants at the same time every evening and uncover them at the same time each morning. A missed day or irregular timing can confuse your plants, cause stress, or slow down the flowering process.
Tips to Avoid Common Mistakes
- Don’t start flowering too early; wait until plants are mature enough to handle the shift.
- Never cover plants too soon in the afternoon; they still need full sunlight to stay healthy.
- Watch for heat buildup under blackout materials, especially in hot weather.
- Always allow airflow to prevent mold during those dark, enclosed hours.
- Use timers or alarms to stay on schedule if needed.
Even small mistakes, like leaving a gap in your tarp or forgetting to uncover plants, can delay flowering or damage your crop. However, with careful planning and consistent habits, forced flowering can become a reliable and rewarding technique.