You can definitely start marijuana plants indoors and move them outdoors at a later time. Doing so can make sense when you want to start your plants in a safe and controlled environment first and then, for example for flowering, would like them outside so they can enjoy the power of the sun for optimal yield. Moving plants outdoors can also be an option if you were to run out of growing space but want to grow your plants to their full potential outdoors.
Unless you are growing autoflowering strains which don’t care about daylight hours and light schedules, the big caveat with moving your marijuana plants outdoors has to do with the natural daylight hours. Unlike indoors where you have control over your lighting duration, you don’t have this control outdoors.
To grow cannabis indoors, it is generally advisable to give marijuana plants a photoperiod of 18 hours of daily light (18/6 cycle). But what happens when we move a plant – that has already received 18 hours of daily light – outdoors in spring?
1. The marijuana plant only receives between 12 and 16 hours of light per day, so this sudden decrease of the photoperiod can make the plant begin the flowering period in most cases.
2. However, as photoperiod increases progressively each day (by some minutes) until 21 June, marijuana plants will stop flowering to go back to the growing period. This natural process, called vegetative regeneration, is both very long and very stressful for the plant. Plants will then form numerous deformed and abnormal leafs before starting to grow again several weeks later.
3. In July, days begin to get shorter and plants flower again, this time definitely. This flowering after vegetative regeneration will unfortunately be poorer in both quantity and quality.
How to safely move plants outdoors?
You have two options
1. Start growing your indoor marijuana plants as usual – in a 18/6 cycle. Many growers who move vegging plants outside wait until the end of June to do so. At the end of June, shortly after the spring equinox, available daylight hours outdoors are the year’s longest which means there is no risk for premature flowering when you move plants from a 18/6 light schedule.
2. Start growing your plants indoors while following the outdoor natural photoperiod. For example, if there are 14 hours of light per day, give your plants 14 hours of light per day as well. You would gradually adjust your indoor light duration every few days for a few minutes to keep the two light cycles (indoors and outdoors) in sync. This would then allow you to put your plants outside without the negative effects of a sudden difference in light duration.
What other precautions should be taken when moving marijuana plants outdoors?
First, you should know that the plant will take some time to accommodate to the new environment, particularly because of light change and environmental conditions. This loss of vigor in the plant can sometimes reduce or even eliminate the benefits of starting the plant indoors.
The strong sunlight, much richer in UV rays than indoor marijuana growing lamps, can be too aggressive for plants that were first grown under artificial lights. Therefore, it is not advisable to expose them directly to the sun, for they should progressively adjust to the sun; then, we should first place the plant in a shady area, and then give it more sunlight day by day.
Inspect plants regularly and control for diseases and pests. Soft indoor leaves are easy-to-penetrate by pests. Once plants toughen up, diseases and pests find them less tasty.
One last important point: while the plants are growing, phytohormones accumulate within their tissues (i.e. leafs). When days begin to get shorter, at the end of June, the level of the plant’s hormone that stimulates flowering increases gradually, day after day, at the expense of the level of growing phytohormones, which begins to decrease.
Flowering will only occur when the plant’s levels of phytohormones are adequate for flowering. This is the reason why the growing period outdoors is longer, so the plant will need more time to flower.