When you cultivate cannabis, there are many considerations before sowing the seeds. Your crops need the ideal environment to produce bountiful harvests—restricted space hinders development. So just how tall does a weed plant grow?
If we could tell you an exact measurement, we would. Many factors determine a crop’s height, including its genetics and the training techniques you implement. Also, you shouldn't forget about cannabis flowering stretching which is a normal process after finishing vegging stage. The sudden growth usually lasts for a few weeks and stops when your plant starts producing buds.
Cannabis plants can grow from 3 to 6 feet tall, but can reach up to 20 feet in some rare cases, depending on the strain, growing conditions, and environment. Indoor grown plants tend to be smaller in comparison to outdoor grown plants.
Do you want to discover how big your plant might get?
We share what the size depends on, what strains' genes have to do with height, and when to grow indoors or out. Join us as we answer “how tall does marijuana grow?” and provide expert tips to keep their size in check.
What does the height of a plant depend on?
Cannabis crops come in all shapes and sizes. Some remain as short as a couple of feet, while others stretch like trees and can reach 34 feet. A few factors determine their overall size—some you control and others you can’t.
- Genetics: Not all weed includes the same heritage. How tall do weed plants grow depending on their genes?
Indica marijuana crops usually stay small and bushy, whereas sativas get tall and skinny. Autoflower strains usually remain short thanks to their ruderalis genetics.
- Indoors or out: When you plant seeds inside, you have complete control over their environment, affecting their overall size. How tall do weed plants get indoors? Most cultivators try to keep crops to 6 feet max.
In the open, cannabis plants stretch and reach their full height potential without vertical limitations.
- Training techniques: If you want to keep plants small, implement bending and tying low-stress training (LST). Many indoor growers use the Screen of Green method (ScrOG) to encourage horizontal growth and better illumination for buds to develop.
Alternatively, other gardeners keep plants in the vegetative phase for longer to get taller and produce larger yields.
Below, we explore these factors and discover to what extent they affect overall height.
Sativa vs. indica vs. ruderalis: when genetics matters
Once you decide to plant indoors or out, it’s time to choose the right strain. Catering to your cultivation space means crops need less training which avoids stress.
If you grow cannabis outdoors, pick sativa seeds. These crops grow tall and have a slim build. They developed in warmer parts of the world and love hot and humid conditions. How tall can a weed plant grow when it has sativa genes? Over 20 feet when it has the space.
Indoor gardeners prefer indica seeds. These herbs remain short and bushy, making them a favorite for gardens located in a closet or on a balcony. How tall do indica grow? Usually between 2–4 feet but can reach 12 feet if left to stretch.
Autoflower strains include sativa or indica genetics plus ruderalis. These added genes mean plants switch to flowering at a certain age and don’t rely on a change in the light cycle.
As for autoflowers, they can't grow really tall. Cannabis with ruderalis genetics grows faster and remains short—usually between 1.5–3.5 feet. Most gardeners sow these seeds indoors due to their small stature. They also provide bigger yields inside than outdoors.
Indoor vs. outdoor growing
One of the most important factors in estimating the overall height of your marijuana is your decision to grow it indoors or out.
As we mentioned, cultivating inside means you control the environment and need to keep crops relatively short due to height restrictions. You decide the temperature, humidity, and light your cannabis receives—impacting how it develops.
Growing indoors doesn’t mean you need to settle for smaller yields. Implement horizontal training techniques by tying tall weed plants to a trellis or ScrOG net. These methods ensure buds receive more illumination and become fat and juicy by harvest.
So, how tall can weed plants grow indoors? In theory, they can’t get bigger than the space available. Growers tend to keep them to 6 feet tops, but by encouraging them to branch horizontally, they can develop much larger.
Sow your cannabis seeds outdoors and expect tall marijuana plants. Without height restrictions, crops reach for the sky with plenty of sunlight and space for roots to stretch.
Certain factors make cultivators want to maintain small plants outdoors, including keeping them out of sight. Make use of a trellis or pick the right pot size. The more room roots have to expand, the bigger the crop. Choose a small pot to stunt growth if needed.
The importance of the stages of cannabis growth
Cannabis plants don’t grow at a steady rate. There are four phases to a crop’s life cycle, and they develop at varying speeds in each one. How tall does a weed plant grow during each stage? How do the phases affect the final height? We find out below.
Germination
The first stage of a marijuana crop’s life is germination. The process encourages a small taproot to sprout from the seeds and poke through the growing medium. How tall are weed plants after germination? Once it’s a few inches tall and develops its cotyledon leaves, it enters the seedling stage.
Seedling
Marijuana is very delicate during the seedling phase. Crops need 18–24 hours of light and need the medium to remain moist to grow faster. In this stage, leaves begin to appear with more fingers as the seedlings stretch. You’ll spot the first “classic” cannabis leaves up to 4 inches above the first cotyledon ones. They grow in pairs on either side of the stem and usually have seven fingers—they can produce up to thirteen.
How tall do marijuana plants get during the seedling stage? When crops are ready to enter vegging, they have seven sets of leaves and are around a foot tall.
Vegetative
The vegetative stage produces the most explosive development in cannabis plants. The stems thicken, and foliage spreads fast. During vegging, crops can grow as much as 2 inches in 24 hours. To encourage quicker and taller development, ensure you supply plenty of water, nutrients, and light. If you wish to control their height, now’s the time to implement training techniques.
How tall is a weed plant when vegging ends? This is where height varies most. Some cultivators extend the time in this phase by continued exposure to lots of illumination. The longer plants spend on the stage, the taller they become.
Vegetation lasts 3 to 16 weeks, with most growers switching to flowering after 4–8 weeks. Average plants reach 4 feet tall by the end of this phase, but it can be much more.
Flowering
When the illumination changes to 12 hours of light and 12 of dark, cannabis plants switch to the flowering stage. In this phase, crops put most of their focus on producing their scrumptious nugs, encouraging further stretching.
How tall does a marijuana plant grow while flowering? Expect to see crops thrive, sometimes becoming double the size of their pre-flowering height. Experts urge you to avoid training at this late stage, or you risk affecting the final yield.
You know buds are ready to harvest when growth slows down. The nugs’ pistils turn brown, and the foliage goes yellow.
How can you control the height of weed plants?
Some growers prefer to keep crops small when growing indoors or hoping to keep them away from prying eyes. You know how tall weed plants can get, but how do you control the height? Implement the training techniques mentioned earlier to tame the size while improving cannabis yields.
- Low-stress training (LST): These methods aim to flatten the canopy. Crops enjoy more light exposure to encourage bigger buds to develop, helping you produce bumper yields.
While the techniques boost final harvest, they also keep plants to a manageable height. Popular LST methods include tying and bending branches in place
- Screen of Green: This technique is similar to LST but requires a net, screen, or trellis. ScrOG forces plants to grow horizontally and keep them short. The broader canopy allows more light on bud sites, improving the yield.
How tall do cannabis plants grow with a ScrOG net? No more than a few feet. Put the screen a foot above the base of your crops to avoid them getting too tall.
- Topping: This pruning method is popular before crops start flowering. With shears, cut away the tips of branches. This encourages marijuana to focus more on bud production rather than stretching upward.
Growers use this method more for sativa strains as they develop into tall marijuana plants.
You have the final say
So, how tall does a weed plant grow? It depends on various factors—genetics, growing conditions, and training techniques. If you’re an indoor gardener, pick an autoflower or indica strain for their compact stature. Keep plants small by using LST methods.
If you prefer to grow outside, sativas are the best choice. These crops become tall and lanky when given plenty of sunshine and root space. Use smaller pots to stunt growth if needed.
Want to learn more about growing cannabis and how to get the best results from your garden of green? Check out our blog full of articles from industry experts on everything marijuana-related.
Are you looking for a specific strain to fit your cannabis garden? Head to our store to find the right marijuana seeds for your growing space.
Frequently asked questions
We've put together some common questions and our expert responses to give you the most information possible about tall weed plants.
How tall should my weed plant be?
There’s no right or wrong answer regarding how tall a crop should be. Sativas are taller and indicas smaller, but there’s no definitive size guide that determines the correct size.
How tall do outdoor weed plants grow?
Without space restrictions, outdoor crops can reach their full potential. How tall does a weed plant grow in the open? Unless you’re trying to keep your hobby under wraps, your crop may develop over 20 feet tall. In extreme cases, some strains reach up to 34 feet.
How tall should my weed plant be at 4 weeks old?
After four weeks of growth, cannabis reaches the end of the seedling stage and should be around one foot tall. Autoflowers are shorter as they reach the vegetative phase quicker.
