When and how to move marijuana plants outdoors
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Is it possible to start an outdoor marijuana crop indoors?
Weather conditions in spring can sometimes be whimsical. Indeed, it seems a good idea to start growing marijuana plants indoors before making them flower outdoors. It is possible, but one must take into account some issues in particular, which we will be described in this post.
In spring, in western Europe, the hours of sun during the day (photoperiod) progressively increases every day, going from 12 hours of daily sunshine in March to about 16 hours of sunlight during the day in June. In July the days lenght begin to decrease, which facilitates the start of flowering of marijuana plants between mid-July and mid-August, depending on both the earliness of plants and the latitude where they are grown.
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 (before mid-June)?
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 (different options to start growing outdoors):
1. Start growing your indoor marijuana plants as usual - in a 18/6 cycle - but waiting until the end of June to move them outdoors.
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. When the natural photoperiod increases to 14-15 hours of sunlight per day, you will have to set your timer and add 15 minutes of light per day.
This very straightforward technique will allow you to move your plants outdoors in spring!
Note that these tips do not concern autoflowering marijuana strains , as they are not photoperiod-sensitive; if you wish, you can start your indoor growing (ideally giving them 20 hours of light per day) and move them outdoors whenever you like, knowing that they will flower anyway after 3-4 weeks of growth.
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.
Due to the lack of an acclimatization period, plants exposed directly to the sun may show signs of burn or discolouration (bleaching) in their leafs. Thus, the plant will have to produce new leafs, which will further delay its regeneration.
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. As a consequence, this will delay the harvest time!
Therefore, starting the crop as soon as possible is not always the best option.
Some marijuana strains are well-known for their earliness, for they quickly start flowering from the time when photoperiod begins to decrease. For instance, it's worth mentioning Early Maroc feminised seeds from Philosopher Seeds and Early Queen regular seeds from Mr Nice Seeds.