The flowering stage doesn’t correlate perfectly to the point when you induce flowering in your plants. Actually, cannabis plants will develop flower structures within the first couple weeks of this stage.
The internodes will decrease and the plant will continue to grow upwards (sometimes somewhat more slowly than it was growing before). However, there is a still a lot of growth to be completed in the beginning of the flowering phase of the cannabis life cycle. It’s important to keep this in mind when thinking about how to properly feed your plant!
When your plant begins to mature and develop flowers (yay, buds!) you have to treat it differently. We’ll help you through this exciting milestone with an analysis of how to handle the mature phase of your cannabis plant’s growth.
Many new growers switch their nutrient ratios too early. It’s easy to to do, but remember your plant is still growing at the very beginning of the flowering phase. While it’s true that the plant will need more phosphor and potassium, it’s still growing for a few more weeks! So it still needs nitrogen.
If you stop giving the plant enough nitrogen at this crucial stage, it could develop a deficiency. Right when you’re nearing the finish line, the plant will begin to yellow and its health will decline. Don’t alter your nutrient solutions until the plant shows very clear signs of flowering. You should be able to see stamens and pistils clearly when you change over.
During the first two weeks of the flowering stage your cannabis plant gets taller and the spaces between the leaves (internodes) will begin to shorten. Shortly after this, you will begin to see the first pistils appearing. You’ll know the flowering phase has started in earnest when you see a lot of these.
A little over a week after that, the marijuana plant will stabilize its growth patterns. You can prune away all the buds that are in shadows since they won’t be developing the compact flowers you’re looking for.
At this point, you want to maximize the light and nutrients that will be focused towards developing those precious buds. When you’re pruning, try not to cut off any of the leaves.
Tip: make sure to download my free Grow Bible for more information about flowering stage
It can be tempting to cut off some of the large leaves which shadow the flowers. DON’T DO IT. Your plant needs those big strong leaves to absorb light and keep the flowers developing. Only cut off leaves if they are dead or otherwise compromised.
Temperature, humidity and nutrients
When your plant reaches the flowering stage of growth, you’ll want to modify the environment accordingly. If you aren’t already using them, you’ll want to switch over to sodium vapor lamps: they emit the spectrum of light that is ideal for flowering cannabis.
You’ll be changing the day/night cycles of light exposure as well, shortening the amount of time that the plant receives light during. Many growers favor equal ratios of light and darkness in a 12:12 hour cycle throughout the day.
Once you start this process, make sure you don’t interrupt it! You don’t want to confuse your plant by letting it be exposed to any light during the dark periods of the cycle. Not even once. This sort of illumination interruption can easily cause the plant to change back to a growing cycle, and you could inhibit your potential yield.
You’ll want the air temperature to change between the light and dark cycles as well. When the plant is exposed to light, the temperature should be hovering near 68ºF and 77ºF (20ºC and 25ºC) near the foliage and 68ºF (18ºC) at the roots. Remember that higher temperatures will require accordingly higher levels of carbon dioxide. When your plant is in the dark, you can let the temperature drop down to about 68ºF (18 degrees Celsius).
Keep the humidity at a steady 70%. Keeping this stable will help you avoid any pest issues that could arise during the flowering phase. Now is also the time to switch over to a flowering nutrient solution. As stated above, just make sure you don’t switch over too early.
After several weeks of the 12:12 hour day/night cycle, the marijuana plant will stop growing and start flowering. The initial flowers will appear on the buds. At this point, the plant shouldn’t be producing any leaves at all, and you’ll see small white pistils developing rapidly and multiplying on the surface of the plant.
Some of the leaves will begin to be covered in a thin, transparent resin. This will happen most closest to the flowers. At this point, you can switch over to your flowering nutrient solution. Your plant requires higher levels of phosphor and potassium during this phase to keep up with the change in growth.
Sometimes new growers can be tempted by the buds and the resin being formed. Whatever, you do, don’t hack up your plant to try and ‘taste’ it. It’s still not fully developed, and you won’t learn anything, except possibly what a small yield you get when you cut apart your immature plant before it’s fully developed. The cannabis plant needs time to mature before you harvest.
About a month after the flowering stage begins, you’ll begin to notice more changes that signify the beginning of plant maturity. The buds themselves will expand and distend: that’s normal. It’s good. Your plants will also grow outwards, widening and getting thicker. The number of calyces on your plant will keep rising. The transparent resin you noticed early will darken and develop a strong odor. If you’ve got a good plant, there will be lots of it.
Because of the expansion, the flowers will grow closer and closer together. At this point, the plant will be bearing a lot of weight and will almost certainly require some support. You can create a trellis system with string or wood, or you can use a metal spring system. The metal spring systems are nice because they will actually adjust the weight of the plant as it matures.
Once the marijuana plants have grown extremely closely together, you’ll likely want to lower the humidity a little bit to minimize the potential for mold, bacterial, or fungal development in those spots. It’s hard for air to circulate through the tiny gaps.
Fully mature flowers
Maturity is probably the most crucial phase of development in the cannabis life cycle. At this point, you're just days away from being able to harvest and process the yield you’ve been working on over the previous months. The time you harvest will have a huge effect on the end product.
You’ll notice that the calyces and pistils start to turn red as the plant finishes maturing. The resin will continue to accumulate, getting stickier and heavier with every passing day. The flowers will draw together and close up any remaining space.
This is the point at which your plants will develop a powerful odor. The best way to deal with the odor is the utilization of carbon filters. Just trying to mask it is unlikely to be effective, and will probably just complicate the problem.
When to stop fertilizing
You’ll want to stop fertilizing your marijuana plants about two weeks before the flowering stage finishes. This will allow your irrigation and watering to rinse minerals and nutrients out of the plant, making it safe and enjoyable for use.
Rock wool, soil, and coconut fiber require two weeks, but if you’re using clay pellets, even a week of water rinsing will clean out the substrate. This cleaning process is very important if you want to get a quality product in the end; otherwise there will be a lot of unused minerals drifting around the plant’s insides.
When at least half of the pistils on your cannabis plant have turned red, you are ready to harvest. The resin should be thick, and easily visible to the naked eye. The plant should be very heavy with buds, and some of the leaves might be turning yellow.
As the leaves turn yellow, you can remove them from the plant. They turn yellow at the end because energy is being devoted to the flowering parts of the plant. Just make sure you don’t remove any green leaves— those are still producing valuable energy!
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