When growing Marijuana outdoors, the use of light deprivation techniques can allow a grower to control the number of hours of light the plant will receive. Depriving the plants of light is something that can be incorporated when there are more than 12 hours of available daylight per day. By tricking the plant into thinking that the long summer days are over and the short light periods are beginning you can speed up the flowering process. This means that even if you are growing Marijuana outdoors, you can harvest late blooming plants before the autumn weather arrives.
The amount of daylight in the northern hemisphere in September is around 12.5 hours. Then during winter the days end quickly and sunlight is only available for around 7-9 hours. Plants that normally finish their flowering period in October or even November are very susceptible to bud rot due to the temperatures and weather conditions during these months. By depriving plants of light you can trigger the flowering process earlier, the best time to do this would be in the beginning of July. After July, the hours of light per day will decline, and it will not be necessary to keep covering your plants.
The average amount of hours of light per day in the last few months of the outdoor season in the Netherlands are as follows:
You may only require to deprive a small number of plants or you may have an entire greenhouse to cover. The important thing to remember when growing Marijuana outdoors and using this technique, is to ensure the cover you make is completely light proof. In the event that your cover lets light through at any point, the plant will likely respond with hermaphrodite traits.
A thick black plastic cover that fits over the plant (and its container) can work well, whilst white covers will not usually not keep out all the light. Small plants can even be placed in a shed and kept in the dark. Other methods include to placing the plant in a black plastic bin for the duration of the technique. If you have a terrace for example then bringing the plants into a dark room that will not be disturbed is perfect. This can be laborious work but it can also be well worth it in the end.
There are two ways of depriving plants of light: in the morning or in the evening. It is up to you as a grower to decide which is most suitable, as long as the plants don’t get more than 12 hours of light.
It is however important to be consistent with when you deprive your plants of light. If you start by applying light deprivation in the mornings, then keep doing this in the morning. By switching back and forth between applying light deprivation techniques in the morning and evening, you may not obtain the desired results.
A grower can create space on a windowsill indoors for a plant to grow if your windows let enough sunlight through. You may have a number of plants in a room that is exposed to sun for long periods of time. This a perfect scenario to perform light deprivation as you can simply use a curtain to obscure the daylight. The good thing about this style of growing is that during the night, the plants will be kept indoors where they are safe and sound. By simply rolling down a thick curtain and ensuring no light leaks are possible, this cheap and effective light deprivation technique can produce excellent results in a way that is very similar to growing Marijuana outdoors.
The following video shows that light deprivation can be performed on a massive scale and that even commercial greenhouse growers incorporate this technique. Because light deprivation is completely automated in the video, the grower is able to accurately control the number of hours of light:
There is no need to deprive autos of light and in the event of light deprivation, this will only reduce the final yield. Automatic strains perform best with 13-18 hours of sunlight so the more light the better. If you intend to use light deprivation techniques when growing Marijuana outdoors, keep in mind that this is only possible with photoperiod strains.
Light deprivation can also be used to be able to harvest twice in one year. For example if you have 10 plants, you would grow 5 plants normally and 5 plants with a light deprivation protocol. This way you can harvest half of your crop much earlier than normal. Depending on when you start the light deprivation regime, this could be as early as August. The other 5 plants can then be harvested in October or November after their normal flowering period.
For more tips regarding outdoor growing, please check out our guide to maximizing your yield when growing Marijuana outdoors.