I live in New Hampshire and plan on transplanting some two-month-old marijuana plants outside. I’m starting the seedlings under fluorescents and giving them 18 hours of light a day. Should I reduce the number of hours of light I give them before transplanting them outside?
In the second month of growing marijuana indoors, you should bring the duration of the light cycle down to around 16 or 17 hours per day to keep the plants from flowering when they go outdoors. In late June, they will receive about 15.5 hours of daylight. Indica, indica-hybrid, and other early season plants are more likely to start flowering than sativa varieties.
Your marijuana plants might also have other difficulties adapting to outdoor life. They have been growing under relatively low conditions with the fluorescents and the sunlight will likely burn them with its intensity and the added UV light that plants are sensitive to. To help the plants adjust, place them in the shade at first, and then increasing their exposure to the light over a week-long period.