Indoor cultivators often ask if autoflower and photoperiod cannabis plants can share the same growing environment. The direct answer is yes, but this setup requires careful planning due to the inherent conflict in their light requirements. Successfully combining these two distinct types of cannabis means understanding their unique biological triggers for flowering within a grow tent.
Understanding Autoflower and Photoperiod Light Needs
The fundamental difference between these plants lies in how they transition from the vegetative to the flowering stage. Photoperiod plants rely on a change in the daily light cycle to initiate blooming. They remain in vegetative growth as long as they receive 18 or more hours of light per day. To force flowering indoors, growers must manually switch the light schedule to 12 hours of light and 12 hours of uninterrupted darkness.
Autoflower plants contain Cannabis ruderalis genetics, meaning their flowering is triggered by age and internal maturity, not by light hours. These plants automatically begin to flower, typically within two to four weeks from germination, regardless of the light schedule. Autoflowers thrive under long, consistent light cycles, such as 18 hours of light and 6 hours of darkness (18/6), throughout their entire life cycle.
The Challenges of Shared Light Schedules
The primary conflict in a shared tent environment is that the optimal light schedules for each plant type are mutually exclusive. Photoperiod plants require a strict 12 hours of darkness to produce the hormones necessary for flowering. If this dark period is interrupted by a light leak, the plant can become stressed, potentially revert to vegetative growth, or develop hermaphroditic characteristics.
If a grower switches the tent to a 12/12 light schedule to induce flowering in photoperiod plants, the autoflowers suffer a significant setback. Autoflowers rely on extended light exposure (18/6 or 20/4) to maximize photosynthesis. Placing an autoflower on a 12/12 cycle cuts its daily light exposure by 33% to 40%, severely limiting its growth potential and reducing its final yield.
This trade-off forces the grower to compromise one plant’s potential yield. If the tent remains on an 18/6 schedule, the photoperiod plants will not flower. If switched to 12/12, the autoflowers will produce smaller, less dense buds and underperform. Additionally, the larger size of a photoperiod plant can physically overshadow the smaller autoflowers, further reducing the light they receive and negatively impacting their yield.
Practical Methods for Growing Both Together
Staged Harvest Method
One straightforward method is adopting the 18/6 light schedule as a compromise. Under this cycle, photoperiod plants remain in their vegetative stage while autoflowers receive enough light to complete their life cycle. This strategy allows the grower to harvest the autoflowers first, which typically takes between 8 and 12 weeks.
Once the autoflowers are harvested, the grower can switch the light to 12/12. This change immediately forces the remaining photoperiod plants into their flowering phase. This approach maximizes the autoflower yield and provides the photoperiod plants with a long vegetative period, usually resulting in a larger final harvest.
Staggered Planting
Another technique involves staggering the planting times of the two varieties. The grower germinates the photoperiod seeds first and allows them to grow for several weeks under an 18/6 cycle. The autoflower seeds are then introduced later. This timing ensures the autoflowers finish their entire growth cycle just as the photoperiod plants are ready to be switched to 12/12, minimizing the time the autoflowers spend under reduced light.
Physical Separation
For growers with a larger tent, physical separation is an option, though it is more complex. This involves installing a light-proof partition, such as a temporary wall made of panda film, down the middle of the tent. This creates two distinct zones. One side can receive the 12 hours of darkness required for photoperiod flowering while the other maintains a long light cycle for the autoflowers. This method requires careful management to ensure the barrier is completely effective and prevents light leaks.