You guys are doing a great job at High Times and have for many decades now. Just wanted to say thanks. I’m new to the grow game and have a small garden using a flood-and-drain system. Have just induced flowering by cutting my lights back from 18 hours to 12 hours, but I don’t know if I should cut back on watering and nutrients, and if so how much of each. Thanks again, – Ed.
Howdy Ed, and thanks very much for the kind words. High Times loves all you guys, too. Thanks for the decades of support! And we love first-time growers a lot; way to go starting up a garden!
I choose this question so that I could first introduce other new or first-time growers to the idea of induced flowering. Most of us seasoned growers take this very simple technique for granted and forget that when someone is first starting out this can be an odd concept to grasp.
In short, cannabis is a flowering plant and has both male (or staminate) and female (or pistillate) flowers. These flowers occur on male and female plants, respectively. On male plants, the flowers are generally pollen sacs and contain very little useful material (unless you are trying to make seeds). The female flowers are what we, as smokers, want to harvest and smoke. This is why all growers separate male and female plants immediately – or just kill off the males – upon identification. Males can pollinate females early on in development and no one likes to smoke seeded bud. I will address the technique of “sexing” your plants in a later post, but there are tricks to identifying males early on and preventing any issues like this. (It might help if someone wrote me an email and reminded me to answer that question. Sorry… memory/ occupational hazard issues.)
In order for a female plant to begin flowering, certain standard conditions need to be met, the most common of which is a 12/12 photoperiod. What this means is that the light period for the plant must not exceed 12 hours, otherwise the plant will believe she is not yet in season to flower. Days are obviously longer in the summer in terms of sunlight and, as mentioned earlier, plants have evolved to understand this as seasonal indicators. When the sun’s hours grow shorter nearing Fall (i.e., the harvest season), plants such as cannabis begin flowering.
Indoor cannabis growers generally keep their plants in vegetation using a photoperiod (or light cycle) between 18-24 hours. Savvy growers do not go the full 24 hours, preferring to give the plants some down time and using only 18 hours of light. This is very smart as plants need to recharge and roots grow much faster at night. Once a grower feels the plants are developed enough to flower and produce the type of yield they desire, they trigger flowering by changing the light cycle to 12 hours of light and 12 hours of dark.
This technique usually works for all strains of cannabis plants. Some breeds can be finicky and may require a bit shorter of a photoperiod, while some other (very rare) may not flower at all no matter what photoperiod is provided. In this latter case, it is likely that the strain being grown possesses genetics from the ruderalis species of cannabis. Ruderalis is a hardy, hemp-like species of cannabis, not to be confused with the well-known indicas and sativas. Ruderalis is known as an “auto-flowering” plant and her flowering is usually not triggered by changing photoperiods. Instead, ruderalis can flower for any number of reasons such as plant height, root zone temperature, root ball size, environmental stress and so on. If you have this type of plant, best to move on to something more cooperative (and more potent).
So with all that said, we finally arrive at the original question: Does cutting back the light cycle mean you must cut back watering and feeding programs? In short, no. While it makes sense that you would, because there is more downtime for the plants, the reality is that the plants are now going to be producing their fruit (in the form of buds). This will require just as much energy, if not more. And many growers want robust yields and high potency, both of which require a lot of plant food to be made via photosynthesis. If anything, your plants are working even harder now, even though they have less light in the day to work with.
In fact, many new growers make the mistake of thinking that once out of the vegetative phase, their plants won’t be growing as much any more and fail to plan for any more growth within their garden space. Don’t make this mistake. During flowering you can expect 30-50% more growth, depending on your pruning and trellising techniques.
Thanks for reading, everyone and remember: Grow… And help the world grow, too!