Vegetative and Flowering Cycles

In this video I’m going to discuss the Vegetative and Flowering Grow Cycles

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The vegetative cycle covers the time where you run your lights using the GLR method; 12 hours on, 5-1/2 hours off, 1 hour on, and 5-1/2 hours off.

The GLR method saves from 5 to 12 hours (depending if you use 18-6 or 24 on) of electricity use every day, which is substantial.

Remember your highest cost involved in growing your own weed indoors will be that of electricity.

If you prefer it, you could run your lights 24/7 during the veg cycle. I’ve done it, and really didn’t see much of a difference in yield or timing.

Or you can run your lights 18 hours on and 6 hours off.  Some growers use a 12/12 flowering light cycle from the beginning. The yield is less and the plants are smaller, but they’re also ready to harvest sooner.

Back in the day, everyone ran their lights 24 hours per day.  That said evidence shows that giving your plants a rest from light everyday results in superior plants.

With this in mind, why not save on your electricity bill every bit you can?

Now, because you’re growing weed indoors, the vegetative cycle will be from 30 to 60 days. You can choose to end the veg cycle anytime you want, or even switch to flowering right off the bat if you want.

The first main point to consider when deciding on how long to keep your plants in the veg cycle is the ceiling height that you have in your grow room.

When the plants start flowering, they will grow taller/larger.

It’s hard to say exactly how tall because different strains have different characteristics, but I estimate your plants will grow 4-6 feet taller after you start flowering.

For example, if your plant grows 4 feet during the veg cycle, it could reach 10 feet tall by the end of flowering.

If you do run out of room at the top, beneath your lighting, bend the top of your plant over by tying a string to the top of the plant, pulling it down as far as needed then clipping the string to the side of the pot.

If your hand gets hot holding it over the top of your plants, the lights are too close.

NOTE:  Any time I give an amount of time for growth, it’s not exact. It’s always an approximation because growth over time depends on the strain of the plant you’ve got, your lighting set-up, what you want to grow, growing conditions, etc.

If you veg too long, your plants may become too tall and they’ll be difficult to properly light during the flowering cycle.

You can top the young stems as they grow, however, which should result in a bushier, shorter plant (if you’re not sure what I mean, don’t worry: topping is coming up soon!).

Of course, if you’re growing outside, you don’t have to worry about a lot of this, as Mother Nature will take care of the vegetative cycle and flowering cycle for you.

As your plants grow, you’ll want to trim the large fan leaves at the stem. Be careful not to strip your plant of all its foliage.

Take a few leaves and then wait, allowing the plant to start some new shoots. Then you take a couple more, and so on and so forth. The plants need some leaves left on them, so be careful to keep this in mind and sustain their growth accordingly.

It’s kind of hard to see in the image below, but basically, I’m reaching in and putting my thumbnail at the base of the leaf stem and the plant stalk, and pinching it.

This method is quicker than using scissors when you’re just pinching off a small amount.

NOTE: I completely disagree with severely defoliating your plants, as is prescribed by some growers. In fact, I’ll go so far as to say that it's complete bullshit.

I have experimented with drastic defoliation but, plain and simple, it hurts the plants, not helps them.

Trim and remove large leaves, and thin your plants out a little, but don’t strip them of their leaves completely. Great things happen in the leaves.

When your plants are about 3-4’ tall (measuring from the floor), it’s time to start the flowering.

If you have a lot of headroom, allowing you to raise your lights, you can let your plants grow taller while in the vegetative cycle, knowing you might cut off height if they get too tall; if this happens,  you can trim the top off, which will pretty much stop anymore upward growing.


This is when the fun begins because you start to see the fruits of your labor.

When I commence the flowering cycle, I start with lights running 12 hours on and 12 hours off; then, every 2 weeks, I increase the off time by 30 minutes.

Doing it like this, I’m trying to mimic the end of summer/fall sunlight.

If you don’t know the sex of your plants, you will once the flowering starts (and yes, if you didn’t already know, this matters).

The females have very wispy thin white hairs growing from the middle of each new flower (bud). You can’t miss them.

Some plants will fool you, though, as some males will also show a white hair or two, so don’t make a decision to keep or toss anything until you’re about 2 weeks into the flowering cycle and sure of the sex.

The males will start to form little balls (pollen sacks) and you’ll spot them right away. Once you see a male, get it out as fast as you can.

The male will start producing pollen soon after those sacks form, and if you leave them with your females, you’ll have plants full of seeds instead of buds.

Your plants should be in the flowering cycle for about 50-60 days depending on the strain of plant. Watch your buds closely, looking for any signs of morphing.

That’s when your buds start turning into seed pods. If it happens, it will occur late into the flowering cycle. If you see them forming, it’s time to harvest.

The most potent weed develops when a plant is allowed to mature properly. You’ll want to decide on the proper harvest time by looking at the trichomes.

They’ll start turning an amber color, changing over to this coloring from clear/white. Generally, they all don’t turn amber, but when you see a good amount of them turning, at least 50%, it’s time to harvest.

If you really like the pot you’re growing and you think you may have a problem getting seeds for your next grow, think about sacrificing one female to make seeds. You’ll have to save one male plant for this.

After about 20 days (depends on strain) of flowering you’ll see small buds forming.

Bring the sacrificial female to a separate room with the saved male and grow them together until the little buds form.

Then sprinkle pollen from the male over the female’s flowers.

The flowers will start to produce seeds. Grow her using 12 hours of lights on and 12 hours of lights off until she matures; 45-60 days.

I stop watering the plant and let it dry in the pot for a few weeks after about 50 days.

When your seed pods turn brown you can harvest your seeds.

Everything will be sticky just like a bud and you’ll want to save the pods after you extract the seeds because it’s potent; you will get ripped if you smoke it.

There is no guarantee that the seeds from a female will become female plants but a good estimate is 50 to 60%

This is a photo of a pollinated female. There a few seeds in each dried out bud. Once the seeds are harvested, save the dried leaves and seed pods to smoke. They are potent!!.

How to Tell a Male Pot Plant from a Female Plant


When you’re growing from seed, you have to distinguish the males from the females. It’s not a fast thing, though.

I’ve been growing weed for a long time, and still can’t tell the difference until the plants have been in the flowering cycle for a while.

If I want clones when I grow from seed, I grow the seedlings in the vegetative cycle for a few weeks and then start to flower them (switching from 18 hours of light on to 12 hours of light on) for a short while until I can see the difference.

I do it this way because I want the female clones to be from vegetating females.

First I flower, and find the females, and then I revert back to the vegetative cycle. After another couple of weeks, I’ll start taking clones.

If you’re not worried about clones or this is your first time, grow your plants in the vegetative cycle for about 60 days depending on strain/room height, and then switch to the flowering cycle.

Within one or two weeks, you’ll see the difference in the plants. Remove the males and finish growing your females for around 60 more days.

To tell a male from a female, look for the little pollen sacks (male plants) that start to form, and get rid of the plants (I do save one, in a separate room, in order to pollinate one female for seeds).

Sometimes the little sacks start forming in a couple of days and sometimes it takes a week or two. Some males show little white wisps, just like females, so wait for the sacks to develop before tossing the plant.

Once I have my girls (they have white wispy hairs) figured out, I change the flowering light cycle back to the vegetative cycle.

I start with 24 hours of light for as long as it takes the girls to revert back to the vegetative cycle, about 10 days. You’ll notice weird-looking single leaves growing through the little buds.

Don’t worry about them; you can trim them or let them grow out.

I change the lights to 18 hours of light on for another week and then change to the GLR (Gas Light Routine) for the remaining time in the veg cycle.

I use the GLR because it saves money on the energy bill and the plants start flowering a few days earlier, after making the switch to the flowering light cycle of 12 hours on and 12 hours off.

Even though the plants initially look a little weird, they grow out into normal-looking plants in a short while.

Once you have a group of female plants growing in the vegetative cycle, you can start taking clones when the lower branches get to be around 4″ long or so.

All in all, it can take around 3 weeks to differentiate the boys from the girls, so it makes a lot of sense to keep a mother plant growing so that you can take female clones anytime you need them.


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