Cannabis Vegetative Stage (Beginner Guide)

Cannabis Vegetative Stage (Beginner Guide)
vegetative stage marijuana 1

In this course I will keep a grow journal about the development of the plants and all actions I take.

I will make photos every Monday, Wednesday and Friday, and write a little report.

In this way you can see exactly what you need to do and what your plants should look like.

During the vegetative stage the plants get 18 hours of light and 6 hours of darkness.

As long as they get 18 hours of light they’ll stay in the vegetative stage.

As soon as the plants are big enough I’ll force them to flower by giving them 12 hours of light and 12 hours of darkness.


Day 1

  • Air temperature: 73
  • Water temperature: 68
  • Humidity: 70%
  • EC: 1.0
  • pH: 5.8

All values are good, so the cuttings should feel comfortable in this climate.

I start every journal with the values I measure when I open the grow tent in the morning.

Keep in mind that the values you see on the photos differ a bit from when I open the tent. This is because the temperature and humidity always drop after opening.

The lamp stays at the very top of the tent for a bit longer, because the cuttings are used to fluorescent lighting and first have to get used to the light. After a few days you can lower the lamp a bit.

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I sprayed the floor and the walls of the tent with a spray bottle to keep the humidity high. The system is filled with water with an EC of 1.0 and a pH of 5.8.

From now on I will measure the values of the water every other day and make adjustments if necessary.

Here’s a list of things you need to check every day to make sure you have the correct values:

  • Air temperature: 68-77
  • Water temperature: 64-72
  • Color of the water: clear
  • Smell of the water: neutral
  • pH: 5.8
  • EC: 1.0 – 1.5 (during the first weeks)
  • Color of the plant and leaves: green

If you stick to the daily routine, you will catch problems in time. I’m still doing it too:

I always check in between and underneath the leaves for discoloration, spots or other deformities that don’t belong there.

Measure the values of the water and see and smell if it’s still fresh. If you keep a small log, you can always look back at the values from a couple of days ago.

If you encounter any problems, you can always consult one of our grow experts on the forum.

They can help you best if you keep a log of pictures and all values. So you can do yourself a big favor by taking a picture every other day.

Enjoy the sound of the bubbling water a bit more and read this article on pH. The pH value indicates how acidic or basic a substance is.

The pH value around the roots has to be right in order to optimally absorb all nutrients.

Plants can not absorb all nutrients if the pH value is incorrect.

This leads to a shortage or surplus of certain nutrients in the plants, because they’re unable to properly absorb them.

The pH values are very important in a hydro system, so you can’t go without a pH meter.

Make sure you read the article on pH, so you know how to measure and adjust the values.

Let my free marijuana grow bible be your ultimate guide as you begin your marijuana journey.

Day 3

  • Air temperature: 74
  • Water temperature: 69
  • Humidity: 70%
  • EC: 1.1
  • PH: 7.1

The plants look healthy and I see a bit of new growth in the main top, so that’s a good thing.

The roots aren’t growing out of the pot yet, but they’re active. The temperature with the lamp on increased a bit above 77 degrees.

The electric heater that automatically switches on when the lights go off makes sure it never gets colder than 63 degrees.

The EC value of the water is still 1.0. This is logical, because the plants barely use any water, and therefore barely any nutrients.

The pH value increased however, which surprises me a bit. Maybe I didn’t clean the pots well enough or the clay pellets influenced the pH level, although I doubt that.

I just add some pH down (available at Amazon) to the water until the value is back to 5.8 to solve the problem. A couple of drips suffice.

This is something to keep a close eye on, which is why you always have to measure the values of your water.

Distance between lamp and plant


This is the ideal distance for a good distribution of the light with a maximal intensity.

The lamps do however generate a lot of heat, so make sure it doesn’t get too warm underneath the lamps.

It’s always a good idea to aim some fans between your lamps and the plants to ensure a proper air circulation.

These also blow away some of the heat the lamps generate. I have a rotating fan on the other side of the tent, aimed exactly above the top of my plants.

Hanging a lamp on top of marijuana plants during vegetative stage
Hang the lamp a bit higher

You can also turn up the extractor a bit to cool off the air. This is the time to connect an active inlet in case you don’t have one yet.

If you can’t get the temperature under control, it’s better to hang the lamp a bit higher.

Don’t forget: it’s not about the radiant heat but about the air temperature. Read more about the ideal temperature in this article.

I attached the air hose to the water hose, so it all looks a bit better. And I bought a thermometer with a sensor on a string with a min/max function.

This means that you can see the current temperature, but also what the highest and lowest temperatures have been after the last reset.

I put the temperature sensor on the string in the water to be able to also monitor the water temperature.

Day 5

  • Air temperature: 74
  • Water temperature: 70
  • Humidity: 60%
  • EC: 0.9
  • PH: 5.8

The plants are looking better and better. Cuttings generally need a week to get used to their new environment before they start growing hard.

The EC was lowered by 0.1, so the plants used quite a bit of nutrients already. The pH remained the same, as it should.

The first little roots are growing out of the pot, which is a good sign. This means the plants ‘took’.

As soon as they have little roots, they can start transporting water and nutrients and grow. You’ll see they will start growing very fast next week.

(pics eerste wortels) Since the plants, and especially the roots, will grow quickly for a while, they need sufficient nutrients.

That’s why I’m going to increase the EC of the water to 1.5. I add this directly to the system, so it has an immediate effect on the plants.

What is EC?

The acronym EC stands for Electric Conductivity. The EC value is the salt content or the amount of nutrients in the water you’re giving your plants.

Demineralized water is purified water, void of any minerals and salts. This has an EC value of 0 and a pH of 7 (neutral).

Tap water contains all kinds of minerals, such as calcium, magnesium and potassium.

Depending on where you live, your tap water has an EC value between 0.2 and 0.5.

This is far too low for plants and the tap water not nearly contains all nutrients our plants need.

I’m giving them a simple A B fertilizer from my local grow shop, similar to this product from humboldt.

This is a complete fertilizer that contains all nutrients marijuana plants need in their vegetating and flowering stage.

2 parts of A and 1 part of B during the vegetative stage because they need more nitrogen.

Read more about EC in the article What is EC.

Day 8

  • Air temperature: 75
  • Water temperature: 70
  • Humidity: 75%
  • EC: 1.4
  • PH: 5.8

The plants are looking good and the new growth has a nice light green color.

The root system keeps growing, so the plant will soon start to grow very quickly.

The temperature of the water in the room is also perfect, as well as the humidity.

The EC dropped from 1.5 to 1.4, so that means that they used some nutrients again.

The pH remained the same, and it seems that the plants didn’t evaporate much water yet.

Then again, they’re very small and use maybe about 1.75 ounce a day. The photos below show that the roots grew quite a bit.

If you want you can connect the water reservoir to the header pot starting today.

The plants are healthy and the roots are growing well. The header pot includes a float switch that floats on the water.

Once this float switch drops below a certain level, the connection with the water reservoir is opened and water flows into the system until the water is high enough.

The float switch will then automatically close the connection.

The water reservoir has to contain water with an EC of 3.0 and a pH of 5.0. When the plants evaporate water and use nutrients, this is automatically replenished.

The reason the EC in the reservoir is so high is because the plants use relatively more nutrients than water.

This causes the pH to increase, so it’s a bit lower in the reservoir. In this way, the EC in the system will always be at 1.5, and the pH at 5.8.

Since I’m in my grow room almost every day, I just measure everything directly in the header pot myself.

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What is humidity?

The acronym EC stands for Electric Conductivity. The EC value is the salt content or the amount of nutrients in the water you’re giving your plants.

Growers are always talking about humidity. But what is it exactly and why is it so important? humidity is the amount of moisture in the air, expressed in percentages.

The humidity is very important to marijuana plants, because it determines the degree of evaporation.

The lower the humidity, the higher the vapor pressure, so the more water and nutrients your marijuana plant can absorb.

But if the vapor pressure gets too high, the plant will protect itself from dehydration and close its stomata.

This causes the plant to barely absorb any water, leading to stagnating growth.

Read this article about humidity to find out what it exactly is and what influence it has on your marijuana plants.

You’ll also learn how to increase and decrease the humidity.

Day 10

  • Air temperature: 75
  • Water temperature: 72
  • Humidity: 60%
  • EC: 1.3
  • PH: 6.0

They’ve grown nicely over the past two days.

The temperature and humidity are perfect, and the heat that’s produced by the circulation pump always keeps the water temperature around 68 degrees, because it also pumps water around when the lights are off.

The EC dropped to 1.3, so I increased it back to 1.5. I once again lowered the pH to 5.8. It’s important to regularly check and adjust these values.

The roots have grown quite a bit and they’re looking healthy. They’re also starting to branch out, as you can see from the long strings with small offshoots.


Since I’m only growing 4 plants in a room that’s 4 x 4 foot, I’ll be fimming the plants today.

Fimming the plant will give it more main tops and makes it wider and not as tall. Fimming is simply removing a part of the new growth from the main top. 

Topping is the removal of the entire top, whereas fimming consists of the removal of about 2/3 of the top.

This leads to more main tops, up to 4 for each fimming action.

A maximum of 2 main tops will arise when topping a plant.

Check this short photo series on how to fim below, and read this article for more information on fimming.

You’ll see that the plants will develop even more side branches and won’t grow in height as much for a while.

I will probably have to fim them again and they can be put into their flowering phase in a week or so.

Keep the humidity in your grow room nice and high and the temperature between 68 and 77 degrees.

Smell the water in the bubble buckets from time to time to see if it’s still fresh.

It’s a good idea to change this a number of times during each harvest.

If you have any questions or uncertainties, don’t hesitate to consult our grow experts on the forum.

Day 12

  • Air temperature: 77
  • Water temperature: 70
  • Humidity: 60%
  • EC: 1.4
  • PH: 5.9

All values are perfect, they actually have been perfect the entire time.

If you have problems gaining control over the climate, check out the Climate section.

This provides all possible information on temperature, light, humidity and air circulation, as well as tips to adjust these values.

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The plants reacted well to the fimming I performed two days ago. The pictures below show that the wound almost healed already, and a bit of new growth is visible.

Since there are only 4 plants on 13 square feet, I think I will have to fimm them again.

In hindsight, a fifth plant in the center would’ve been chill. We just have to let them grow a bit longer for the entire surface to be covered with leaves.

I noticed that the top roots are a little bit yellow. As roots get older, they can become a bit yellow, which is not a problem at all.

This especially happens to the roots that aren’t placed in the water. It is however something you should always keep an eye on.

Each time you check your plants you should check the quality of the water.

Checking the water

In addition to the EC and pH values, you have to check if the water is still clear.

Just scoop a glass of water from the system and see if it’s nice and clear and that nothing is floating in it.

Also smell the water by sticking your hand in and smelling it. You should actually smell nothing. Problems often start if the water isn’t being pumped around properly.

It will start to smell like stagnant water. You probably recognize this smell from your washing machine, after leaving your washed clothes in too long.

Or after opening a tap that hasn’t been used in a long time.

If the water doesn’t circulate well, harmful bacteria have the chance to settle, possibly leading to algae or root rot.

In this case you should immediately change the water and thoroughly clean and flush your system.

In order to kill any residual harmful bacteria you could add a bit of hydrogen peroxide (3%) to your water.

Use 1 to 3 ml per 32 ounces of water.

This weekend I’m going to get a bottle of hydrogen peroxide and I’ll add some to the water on Monday.

If the roots look worse on Monday I will replace all the water and clean the entire system. But I expect everything to go well.

Read more about water in the Watering section.

Day 15

  • Air temperature: 75
  • Water temperature: 71
  • Humidity: 70%
  • EC: 1.1
  • PH: 5.9

They’ve grown nicely over the weekend. Much new growth is visible and quite a bit of water evaporated, so they also absorbed a lot of nutrients.

I see that the leaf tips are very slightly burnt, so I’ll take it easy with the nutrients for a bit. I’ll drop the EC to 1.0 for the next couple of days.

The pictures below show you what burnt leaf tips look like.

For maximal results you have to try and give them as much nutrients as they can take.

But this comes with risks that can negatively influence the final result. If you prefer security, it’s best to start with an EC of 1.0 and slowly increase it to 2.0.

I will try to get to 2.8 without the plants suffering from nutrient burn. All circumstances need to be perfect in order to do this.

The roots are looking really great. They’re nice and white and grow just as hard as the plants themselves.

The pictures below show the difference between healthy roots and rotten roots.

Especially the part that hangs in the water will turn brown. A proper water circulation and sufficient oxygen are key for this way of growing.

Hydrogen peroxide

The water is still looking fresh and doesn’t smell like anything, so there are no harmful bacteria in the water.

I’m still adding some hydrogen peroxide. This substance has a similar chemical structure to water, but it has an additional oxygen atom. That’s why it’s also called oxygen water.

It is used as a disinfectant for drinking water, for instance, as bleaching agent for teeth, but hydro growers also love to use it.

The extra oxygen atom causes hydrogen peroxide to increase the availability of oxygen for the roots.

More nutrients can be absorbed by the plants because of the high oxygen levels, enabling them to become bigger can grow more buds.

It’s important that the water temperature is around 70 degrees. This is the ideal temperature for the roots to absorb as many nutrients as possible.

Take hydrogen peroxide with a concentration of 3% and add 1 to 3 ml for every 32 ounces of water.

I start with 1.5 ml per 32 ounces and increase this to 3 ml per 32 ounces during the flowering stage.

There are about 25 gallons of water in this system, so I add 150 ml of hydrogen peroxide.

Hydrogen peroxide has a pH value of 3.6. Take this into consideration when adding it to the water.

Always measure the pH of your water before you add the hydrogen peroxide to it and measure it again after adding it.

In my case, the pH value was 5.9 before adding it, and 5.8 after adding it, so it’s all good.

As a precaution I usually change the water in my system once a month.

The plants have been in the system for 15 days now, so I’ll be changing it at the end of next week.

I will then also increase the amount of hydrogen peroxide to 2 ml per 32 ounces, and a month later to 2.5 ml, and eventually to 3 ml per 32 ounces.

Day 17

  • Air temperature: 75
  • Water temperature: 72
  • Humidity: 60%
  • EC: 1.0
  • PH: 6.0

These plants are still looking good. They’re nice and green and starting to get a nice amount of side branches.

The temperature with the lamp on is around 75 degrees, and it never gets colder than 64 degrees with the lamp off.

All other values are also perfect, and it shows in the plants.The water is still fresh and the EC value dropped to 1.0.

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Since the new growth has no burnt leaf tips, I increase the EC to 1.3 and check how they’re doing the next time.

This is the main advantage of growing on hydro; you can instantly adjust all values. I also lower the pH again to 5.8.


Sooner or later, every grower will encounter bugs. I’ve had many different grow locations, and no matter how clean you keep them, bugs will always find their way in.

You should therefore check your plants every day or every other day for bugs and diseases.

See if the leaves show spots or discoloration and check underneath the leaves for bugs. You can find some examples below.

This is a type of mite that feeds on plant saps. Damage is visible on top of the leaf, in the form of white spots.

Spider mites damage on marijuana during vegetative stage
Spider mites

The bugs themselves are located underneath the leaf and look like very small black dots.

If there are a lot of spider mites, they can create webs around your leaves and buds, which are very harmful to your plants.

These bugs can easily be treated with Bug Blaster or anything else based on pyrethrin.

Thrip damage on marijuana during vegetative stage

Thrips belong to the smallest winged insects. They can cause major damage to your marijuana plants, because they feed on the plant saps inside your plant.

They do this by scraping over the leaf, creating a type of silver-grey spots on them.

Thrips can easily be treated with Bug Blaster or anything else based on pyrethrin.

I know the mother plants of these cuttings were affected by thrips.

And since there are some light spots on my leaves, I’m going to preventively treat them with an agent based on pyrethrin.

This is an organic agent that’s extracted from the oil glands of chrysanthemums.

It kills all crawling bugs, such as lice, spider mites, thrips, and can be purchased at garden centers or on Amazon through this link.

Read the instructions on the label for the right concentration and thoroughly spray your plants.

Make sure you especially spray underneath the leaves, because that’s where most bugs are located.

Repeat this treatment after three to five days to kill young bugs that just hatched.

The oil remains visible on the leaf for a few more days after evaporation of the water. Don’t confuse this with damage to the leaf.

Day 19

  • Air temperature: 77
  • Water temperature: 70
  • Humidity: 60%
  • EC: 1.1
  • PH: 5.9

Everything is looking great and the values are perfect. The EC dropped to 1.1 again, so the plants did a good job absorbing the nutrients.

I’m going to increase the EC back to 1.3 and see how they react to that. The pH is at 5.9, so that’s fine.

As you can see in the above pictures, the plants are very healthy. The root system continues to grow and has a nice color.

I am going to install a water purification system next week and change the water.

The leaves are nice and green and don’t show any signs of discoloration, deformation, or other unwanted symptoms.

The last time, I preventively sprayed against bugs, so it’s important to check your leaves for new damage or bugs that are still crawling around.

It’s possible that some new eggs will have hatched, so it’s always important to repeat the treatment after some days.

The leaf in the picture below looks perfectly healthy. It has a beautiful dark green color. Same for the roots. Couldn’t be better…


You can sometimes see the thermometer in pictures, but this doesn’t always show the correct values.

In order to take nice pictures I have to turn off the MH lamp and turn on the studio lamps that are hanging from the ceiling.

This quickly cools off the room and lowers the humidity. The values are all right in this picture below by the way ;).

Bringing humidity down during marijuana growing
Lowers the humidity


The plants have to get a bit wider to cover the entire tent. That’s why I’m going to fim them again.

Now, there are multiple main tops, and I’m going to fim them all.

The plant will create even more main tops this way and the side branches will come up higher a bit. The pictures below explain exactly what you need to do.

There are more pruning techniques, such as topping, low stress training and super cropping.

Check the grow skill section and start with this article on pruning.

Day 22

  • Air temperature: 75
  • Water temperature: 70
  • Humidity: 70%
  • EC: 1.0
  • PH: 6.0

The plants evaporated a nice amount of water over the past two days: I estimate about four gallon.

This means they’ve also absorbed a lot of nutrients. I add water to the system and make sure the EC value gets back to 1.3 and the pH at 5.8.

I also hang the lamp a bit higher, because the plants are growing fast.

If you click on the left picture above, you see the new leaf is a bit deformed. That’s the result of fimming.

Since you don’t cut off the entire top but only a part, you always end up with some deformed leaves.

The picture on the right shows that the wound restored nicely and that new tops are developing already.


The plants are growing closer and closer to each other, so I think they can go into the flowering phase at the end of the week.

These amnesias are Sativa dominant, so they grow faster than Indicas.

If you only want to, or are only allowed to, grow a couple of plants and you want to optimally use your light, it’s best to choose a Sativa-dominant strain and prune them very well.

When forcing them to flower, the plants also need different light.

You have to replace the MH lamp with an HPS lamp, which provides more orange-red light, promoting the flowering.

The more light a plant gets, the higher the yield, but you have to use the right type of light. You can’t grow with regular light bulbs.

Read this article about light and learn why a plant needs light and what happens with the light as soon as it hits the leaves.

I also explain what types of lamps can best be used and how the light cycle of a marijuana plant works. Read more…

Day 24

  • Air temperature: 77
  • Water temperature: 70
  • Humidity: 70%
  • EC: 1.0
  • PH: 6.0

The temperature and humidity are still perfect. The temperature of the water and the values of the water are also fine.

And this really shows in the plants, because they look beautifully green.

In two days I will bring them into the flowering phase and replace the 400 watt MH with a 600 watt HPS.

I start the flowering phase by simply changing the duration of light from 18 hours a day to 12 hours a day.

But before doing this, I first change the water.

Despite the water still looking and smelling fresh, there are some deposits on the buckets, hoses and connecting pieces.

This is not a problem, but it never hurts to change the water and clean everything.

I will also install a water purification system that is similar to the ones used in aquariums.

Clean the inside of the buckets, the air hoses and all connecting pieces with the water still in the bubble buckets.

Now take all the dirty water out of the buckets and thoroughly clean everything.

Don’t use cleaning solution. Fill the system with water with an EC of 1.4 and a pH of 5.8.

This water filter is very simple. Place both hoses in the water you want to purify. One hose sucks the water into the filter.

The coarse dirt is first picked up by a couple of sponges. The water will then move along purifying stones to catch algae and other small organisms.

The purified water will then be injected back into the buckets.

Always test the system before making it to size. In the first picture I just placed it in the old water to test it. I cut the hoses to size later.

Everything is nicely connected in the second picture.

A pump like this is definitely not a necessity and is more of a luxury.

Whenever I make my own bubble buckets, I usually install a circulating pump with filter to keep the water clean, because some algae and other organisms will always grow in any system.

Day 26

  • Air temperature: 78
  • Water temperature: 71
  • Humidity: 70%
  • EC: 1.2
  • PH: 6.1

When looking at the pictures above, you can see that the leaves of the plants are touching each other.

This means it’s time to force them to flower. These Amnesias will grow at least another two weeks from the moment you start the flowering phase, so this grow tent will eventually be completely grown closed.

Measure the pH and EC and adjust the water so the pH is 5.8 and the EC is 1.5. I keep the EC on 1.5 from now on and raise it by 0.1 every week, ending with 2.4.

I now move on to bloom fertilizers by Flower Power, and I will give a booster in a couple of weeks.

Check the roots again, because this gets more and more difficult. Especially when we’re going to support the plants with nets, so they don’t fall over.

Set the time switch to 12 hours of light and 12 hours of darkness.

During the growing phase, the lights were on from 9PM to 3PM. In the flowering phase they’re on from 930AM to 930PM.

I now turn them on during the day, because my colleague and I are always at the growing location at 9AM to take pictures.

It’s often cheaper to turn the lights on at night, because it’s colder, so you won’t have to provide as much additional heat during the day.

I replace the 400 watt MH with a 600 watt HPS. This HPS provides more orange-red light, promoting the flowering.

Take into account that this lamp generates more heat, so place it at the correct height, ideally between 20 and 25 inch without the tops getting too hot.

Place your hand at the height of the tops. If it starts to burn on your hand, it’s also too warm for your tops. A fan can provide some cooling.

The vegetation stage is completed and the plants are looking good. The root system is nice and white and already very big.

This will continue to grow until week 5 of the flowering stage. The plants have a nice green color and don’t show any stress symptoms.

In a week or two, the first little buds will become visible. So far I’ve been very satisfied with this system.

Unfortunately it’s only available in the UK, but if everyone starts emailing they might start selling them in the States as well.

This is their website: If you want to buy a similar system, check out this setup from Dealzer.

First 4 weeks of flowering in a month….