I reside in Florida where the summers are extremely harsh and the springs are a little more conducive to growing. How old or tall should the marijuana plants get before they can make it outside?
When placing marijuana plants outside between early September and early February, be prepared for them to flower immediately as long as there aren’t that many passing cars or streetlights to worry about. This is because they will receive 11 hours (or more) of darkness. Indicamarijuana plants, even rather small ones, cease growing after they switch from the vegetative stage to the flowering stage. They tend to grow about 25 to 50% taller than when they were forced. Sativas will continue their growth even into the flowering stage until they reach a larger size—around 4 to 5 feet high). Indica-sativa hybrids grow more than indicas and less than sativas.
You can place marijuana plants outside at any stage. It really all depends on how tall you want them to be at harvest time.
For instance, you can take early-ripening plants that started to flower in the winter and force them into vegetative growth using incandescent lamps or a strong flashlight to interrupt the night cycle. This should be done every night at least several hours into darkness and/or before dawn. When the plants have reverted back to vegetative growth, they can be forced back into flowering by halting the daily treatment of light.
Sativas that have been put outdoors through early January or indicas by February will finish their flowering stages in early April. When the buds are picked, the plants that remain in the ground will revert to vegetative growth and flower again in the fall.
Spring officially begins on March 22 when the night (dark period) dips below 12 hours. Most marijuana plants will keep flowering for at least another month, so you do have some wiggle room in the planting schedule.
In order to force flowering in the spring, you should shade the plants every evening and remove the tarp 12 hours later. Continue this throughout the flowering stage.