Learn About the Cannabis Vegetative Stage

Published Mar 18, 2019

by Nebula Haze

The vegetative stage is the first stage of life for a cannabis plant. It is a period of growth where a plant focuses on getting big and strong.  When a plant is only growing just stems and leaves (without any buds), that plant is considered to be in the vegetative stage.

These cannabis plants are in the vegetative stage. They’re only growing stems and leaves, without buds.

Cannabis plants in the vegetative stage under a 315 CMH grow light

Cannabis Life Stages

  • Vegetative – stems and leaves
  • Flowering – making buds / flowers

Indoor growers can keep cannabis plants in the vegetative stage for as long or short as they want by providing at least 18 hours of light a day. This is usually accomplished by putting grow lights on a timer. Unlike outdoor growers who are reliant on the sun cycles to get plants to start making buds, indoor growers have more control over the final size and shape of their plant.

The exception to the rule about light schedules is auto-flowering strains, which automatically go from start to finish in about 3 months regardless of what light schedules they receive. Learn more about autoflowering strains.

Having a light period that lasts 18+ hours each day will make cannabis think that it’s summer/grow time. As long as cannabis plants get 18+ hours of light a day, they will remain in the vegetative stage, growing only stems and leaves.

Use a timer to automatically turn indoor grow lights on and off

Use a timer to automatically turn cannabis grow lights on and off

Indoor growers usually provide either a 18-6 or 24-0 light schedule during the vegetative stage of cannabis. 18-6 means 18 hours of light and 6 hours of dark each day. 24-0 means 24 hours of light with no darkness each day.

18-6 vs 24-0 Light Schedule for Indoor Growing

Some people will keep their lights on 24 hours during this stage while others will keep the lights on a schedule where they’re 18 hours on and 6 hours off every day.

Which is better? 

The answer depends on which grower you ask, and may even be different from plant to plant. Most weed strains are fine and will flourish when given 24 hours of light a day in the vegetative stage. Yet some strains may do better on 18/6.

If electricity costs are a big concern, you may want to consider a 18/6 light schedule in order to help keep electricity costs down. This also allows growers to use the 6 hours of darkness to help cool the grow area. If your grow area gets too hot at certain times of the day, you could set your 6 hours of darkness to happen during that time, so lights aren’t running when it’s hot.

If you’re worried about the temperature dropping below 70°F (20°C), then 24 hours of lights a day might be better, because it can help keep your plants warm.

There will always be growers who feel that cannabis plants need some time with the light off (a dark period) in order to have optimal growth, while others believe that the extra hours of light are better since they give your plants slightly faster growth in the vegetative stage.

This cannabis plant in the vegetative stage is loving life

Auto-flowering strains of marijuana need 18-24 hours of light a day from seed to harvest. You sort of treat them like they’re in the vegetative stage and let them do their thing.

I typically keep my lights on and 18-6 schedule (18 hours of light, 6 hours of dark) for all my plants during the vegetative stage (or for autoflowering strains). It’s easy and my cannabis plants grow fast and healthy. I live in a hot climate with high electricity costs, so the 6 extra hours of lights-off is meaningful.

However, I have used 20, 22 or 24 hours of light a day for my cannabis plants, and they grew just fine. If you have your grow dialed in, the main difference is just that plants tend to grow faster. A full 24 hours of light/day certainly provides somewhat faster vegetative growth than an 18/6 schedule because plants are getting more light to make energy. It’s up to you to decide which light schedule is best for you. Anything between 18-24 hours per day works great.

A short, bushy cannabis plant under a MH grow light

On average, most indoor growers vegetate their plants for 4-8 weeks. Seedlings are able to start flowering as early as 3 weeks from germination, but the resulting plants will be small. Most growers choose to let plants vegetate for longer because giving them more time to grow results in bigger plants, which tend to produce bigger yields as long as you have enough light to cover all the bud sites. That being said, you can still produce quite a bit of bud with a lot of small plants growing at once as long as you fill up your grow space.

Daily Care in the Vegetative Stage

In the vegetative stage, your job is simple. Cannabis plants grow fast and are tough in the vegetative stage.

To keep your cannabis happy and healthy, you need to do the following

Provide water – Water plants when top inch of soil feels dry to the touch. In containers, make sure water can drain freely out the bottom. In a hydro setup, there will always be plenty of water. How to water plants.

Nutrients – if providing nutrients, start using the included nutrient schedule at ½ strength, and only raise to higher levels of nutrients if needed. Simply add the directed amount nutrients to your water before giving it to plants or adding to reservoir. Manage pH levels if using liquid nutrients.

Provide light – Use your vegetative grow light as directed. Simply turn grow lights on and keep at the recommended distance from the top of your plants. Outdoors plants will continue vegetating until days start growing short. Indoors plants will stay in the vegetative stage as long as they’re getting 18+ hours of light a day

Not too cold, not too hot – Vegetative cannabis plants prefer a comfortable room temperature or slightly warmer. 70-85°F (20-30°C) is great. Avoid low humidity (below 40% RH) in the vegetative stage if possible. Never allow plants to experience freezing temperatures.

Air circulation – Make sure cannabis gets a constant supply of fresh air so plants get the CO2 they need to grow, and keep air moving so there are no hot spots and leaves are always moving/rustling. Outdoors you may want to put up wind breaks if it gets too windy so plants aren’t being waved around.

Some things to look out for during your first grow:

  • Strange coloring or spotting in your leaves. It is normal a few older and lower leaves to turn yellow or brown and die as the plant matures. It is also normal for all the leaves to start turning yellow in the last week or two before harvest time as your plant pulls nitrogen from the leaves into the mature buds. Other than those exceptions, your leaves (optimally) should always look green and healthy during the whole grow.
  • Keep an eye out for leaves that are falling off, curling up or dying at a rate of more than a couple of leaves every few days. If your plant is losing more leaves than it’s growing, you know there’s a problem.
  • Any sort of rotten or bad smell often indicates bacteria, mold, or rotting. Investigate your system to see if you can find the source of the bad smell. If your plants are starting to smell pretty skunky towards the end of your flowering stage, that’s totally normal.
  • Keep an eye out for signs of mold on your buds or leaves. If you see something on your leaves or buds that does not look like trichomes, you may be seeing the first signs of mold. A common mold looks like white powder on your leaves and is known as “Powdery White Mildew.”
  • Very slow growth means that something is wrong. Use this 7-step checklist to figure out what it is: https://www.growweedeasy.com/7-step-remedy
  • Keep an eye out for “stretching” or when your plant grows very tall with a lot of space between nodes, as opposed to getting bushy and growing lots of leaves. This usually indicates that the plant needs more light and is trying to “reach” for the sun.
  •  Look out for any signs of bugs including mucus trails, eggs, spots, etc.
  •  Watch out for any other signs your plant isn’t growing vibrant and healthy.

Don’t worry about every little thing, but if you feel like your plant may be having some sort of problem, try to identify what it is and fix it as soon as possible! Many times a problem can be fixed if it’s caught in the early stages, and won’t have an effect on yields.

Diagnose my sick plant: https://www.growweedeasy.com/plant-doctor

How often do I water my plants?

Seedlings may need less water at a time until they are growing vigorously. Especially if young plants are in a big container, avoid giving a lot of water at a time until the plants starts growing faster. Once plant is growing new leaves and stems regularly, start watering using the techniques explained below. How to water cannabis properly…

If adding nutrients in the water:

  • Wait until the top of the growing medium is dry about an inch deep (up to your first knuckle – just use your finger to poke a hole in the soil and see if it feels dry).
  • Add water until you see at least 20% extra runoff water drain out the bottom of your pot.
  • Go back to step 1.
  • Note: If water takes a long time to come out the bottom, or if pots take longer than 5 days to dry out before the next watering, you may actually have a problem with drainage
  • How to water: https://www.growweedeasy.com/how-often-water-marijuana

If growing in soil without added nutrients:

  • Try to give just enough water that grow medium gets moistened, but not enough to get significant runoff out the bottom
  • You don’t want to accidentally wash away extra nutrients since you’re not giving any more
  • Beware of overwatering! Soil that’s rich enough to provide nutrients until harvest can be easy to over-water.
  • Learn how to grow plants in soil that provides nutrients until harvest: https://www.growweedeasy.com/organic-super-soil

Some growers also use the “lift the pot” method to decide when to water your plants (basically wait until your pot feels “light” since the plants have used up all the water). It’s up to you to decide what’s easier for you.

 

Is My Temperature Okay?

Vegetative cannabis plants prefer a comfortable room temperature or slightly warmer. 70-85°F (20-30°C) is great. Avoid low humidity in the vegetative stage if possible.

Cannabis plants don't like too hot or too cold temperatures

Make sure to always check the temperature as experienced by your plants, not the ambient room temperature. Check the temperature directly under the light where the top of your plants are located. If temperature feels too hot for your hand after 10 seconds, it’s too hot for your cannabis and you need to take steps to bring the temperature lower. If it’s just a hot spot, you can use small fans to disperse the heat and provide good air circulation in the room.

Cannabis plants cannot stand cold temperatures. Freezing temps can kill cannabis. So if plants are kept in a cold area (for example a basement), take steps to prevent the plants or roots from getting too cold. Grow lights will help keep the plant warm, but make sure the bottoms of the plants have a protective barrier from anything that might be too cold.

Vegetative cannabis plants prefer a comfortable room temperature or slightly warmer. 70-85°F (20-30°C) is great. Avoid low humidity in the vegetative stage if possible.

Learn more about temperature for the vegetative stage of cannabis:
https://www.growweedeasy.com/temperature#seedling-and-vegetative-stage

 

What if I run into problems?

It’s important to keep a close eye on your personal garden during your first couple of grows, and it is inevitable that you will make some sort of mistake or have some sort of problem with your plants.

No grower ever has a “perfect” grow

A good grower always keeps a close eye on their plants, so they can catch and correct any issues before the plant is permanently damaged.

It’s okay to make mistakes. Just keep an eye out and fix them!

Marijuana plants are very resilient, especially in the vegetative stage. As long as you fix any problem that is hurting them, they will usually bounce back quickly and go on to produce fine buds. Problems or nutrient deficiencies that happen to cannabis in the vegetative stage do not have much effect on flowering/budding as long as issues are corrected right away

Here’s a list of marijuana problems, symptoms and cures: https://www.growweedeasy.com/cannabis-symptoms-pictures

 

How Long Should the Vegetative Stage Last?

The length of this stage is a matter of personal preference. Most cannabis plants need at least 3 weeks in the vegetative stage before they will start making flowers, but after that you get to choose how long your plant spends in this stage (unless using an auto-flowering strain), because you’re the one to ‘flip the switch’ and get your plant to enter the next life stage: flowering.

Wait, how do I switch my plant from the vegetative stage to the flowering stage?

When you start with a seed, even with an auto-flowering plant, you will always have at least 2-3 weeks of vegetative growth before any buds start forming no matter what you do. Growers generally allow their plants to stay in the vegetative stage from a few weeks to a few months.

The size your plant achieves in the vegetative stage has a very large effect on your final yields since bigger plants produce more bud sites than smaller plants. However, you need enough light to cover all the bud sites or they will never develop properly. Light is like food for bud growth!

These vegetating plants are about 4 weeks old from germination

Some aggressively vegetating pot plants - healthy and happy!

To give you an idea as to what your FINAL marijuana plant may look like depending on how long it spends in the vegetative stage…

 

This plant didn’t spend any time in the Vegetative Stage. It was given 12-12 lighting almost immediately after sprouting. It’s so small that it spent its whole life in a solo cup, and its only light came from CFLs. I weighed down the bottom of the cup so it didn’t fall over. It ended up yielding about 0.75 oz.

This marijuana plant was given 12-12 light from seed to force the plant to start flowering right away

 

These auto-flowering plants spent about 3 weeks in the vegetative stage before they automatically started flowering, and were ready to harvest just 5 weeks later. They were about a foot tall at harvest and yielded approximately 2 ounces each. Read the step-by-step tutorial to grow plants exactly like this.

Auto-flowering plants just before harvest

 

This marijuana plant spent about 6 weeks in the vegetative stage before being changed over to flowering and yielded just over 6 ounces at harvest. View the complete grow journal with instructions on how to grow your plant so it looks just like this at harvest!

Original Amnesia in regular light

 

These cannabis plants were vegetated for about 8 weeks before being flipped to the flowering stage. Although they were grown in the exact same conditions from seed to harvest, their final heights are remarkably different because their strains had vastly different genetics. The smaller plant produced 6.6 ounces, while the big plant produced 9.3 ounces. Strain can make a big difference! Learn about growing different strains together.

Example of growing different marijuana strains together

 

These cannabis plants were vegetated for about 9 weeks before being flipped, in the exact same setup as above, and produced over 10 ounces each. Besides an extra week of veg, the biggest difference between this grow and the one above was simply the strains.

A view of the cannabis grow tent on harvest day! These two plants each produced over 10 ounces of bud

 

This human-sized plant (one of my very first plants) spent a little more than 3 months in the vegetative stage before I realized I needed to turn it over to the flowering stage. It then spent another 12 weeks in the flowering stage before it was ready to harvest because it was a long-flowering strain. It got way too tall for its space (taller than me!) and started falling over. However, despite the huge size and more than 5 months of growth, it only ended up yielding about 6 ounces. This is because it was under weak CFL grow lights. Though there was a lot of buds, the lack of strong light made them airy, without a lot of weight. Click the picture for a close-up. 🙂

Example of a cannabis plant that got too tall and needed to bent over in order to continue maturing until the proper harvest time

 

Some people put their seedlings or clones right into the flowering stage if they want to harvest quickly though this makes for extremely small plants. For example, super-stealth growers who are growing in small hidden spaces – like out of a computer case – would want to put their seedlings into flowering nearly right away to keep their plants as small as possible. It’s also important to remember that container size and grow lights make a big difference. Small containers constrain the roots and keep plants from getting as big as they could, and small lights prevent buds from fattening up as much as they could.

I personally recommend at least 4 weeks in the vegetative stage with 18+ hours of light each day for the best results. Plants that are forced to start flowering sooner than 4 weeks don’t yield much compared to how much work you put in. That being said, keeping plants relatively small does have some benefits!

A good rule of thumb…

Your plant will likely double in size (maybe a bit less, maybe more) from when you first put it into the flowering stage; this is known as the Flowering Stretch. So make sure you end the vegetative stage before your plant reaches half the final height you want, or your cannabis plants may outgrow your grow space during the flowering stage!

 

Learn about the cannabis flowering stage

 

 

 


 

Question: How do I know when the marijuana vegetative stage is over?

Answer: When the marijuana plant is in the vegetative stage, it only grows vegetative growth like leaves and stems.

In the vegging stage, the plant does not grow buds/flowers at all.

You can tell when the vegetative stage has ended because the plant starts growing gender-specific parts in addition to leaves and vegetative growth.

For example, you know the flowering stage has started when the plant starts growing pistils/white hairs/buds if plant is a girl, and balls/pollen sacs if a boy.

Vegetative Stage vs Flowering Stage Diagram

Vegetative vs Flowering Marijuana plant diagram
Notice how the plant only grows leaves and stems in the vegetative stage

Why won’t my cannabis plant grow buds?

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