How Tall Can I Vegetative Grow My Cannabis In A 7 Foot Tent

What is the Optimal Height for Cannabis Plants?

Nebula Haze is the author of this piece. Is there an optimum height for the plant towards the end of its life? Most of what I’ve read suggests to keep the plant in the Vegetative Stage until it’s about half the height you want it to be, then switch to the Flowering Stage since plants grow roughly twice as tall as they did in the Vegetative Stage. Assuming, of course, that you are able to maintain the cover as flat as possible. Should you attempt to climb as high as your tent/light will allow you to without burning?

Is it possible that the plant is wasting energy by transporting nutrients up a higher plant?

When it comes to indoor cannabis plant training, the ideal situation is for your plants to be large enough to hold as much bud as your grow light is capable of producing.

As a result, while growing indoors, the ideal length of buds is highly reliant on the amount of light available.

Optimal Plant Height Depends on Your Grow Light. Bigger Lights Can Support Bigger Plants and Longer Buds!

You’ll frequently observe long, fat “colas” at the top of an indoor cannabis plant when it’s time to harvest it, with smaller buds beneath them if you look at the structure of the plant when it’s time to harvest it. It appears like the buds become smaller as you move further down the plant’s stem. After a certain point, the buds become so little that they no longer contribute much to the overall weight of the plant. Large buds grow on the surface, but as you move further away from the light, the buds become smaller and smaller until there are absolutely none left.

  • Any further time spent in the vegetative stage would very certainly have been considered a waste of time.
  • Below that point, the plant continued to produce buds, but they were single buds rather than a continuous cola of buds as above.
  • For a lot of strains, here is where the “sweet spot” is located.
  • A larger grow light, on the other hand, may have supported a higher plant.

It’s not a big deal if your plant is too tall as long as it fits in your grow space, but the extra lower growth that doesn’t produce buds is an unnecessary drain on your resources in terms of electricity, time, and money, as you could have potentially cut weeks off your vegetative stage without sacrificing yields!

As a result, I’m not sure how much of a benefit you would receive from moving to 12/12 once the plant has grown to 2 feet in height.

These plants were swapped when they were roughly 20′′ tall and were being grown under a 600W light. Greater grow light intensity allows for even higher plants and longer colas to be supported!

Examples with Common Grow Lights

However, while it is true that you should transition your plant to the flowering stage when it has reached approximately half of the final desired height (because it will approximately double in size after the transition to the flowering stage), the following are some general guidelines that have worked well for me: Note: After you’ve finished growing, attempt to perform a “autopsy” on yourself and check through your photos to see if there’s anything you might have done differently to achieve even better outcomes.

Almost every year, I learn something new.

  • T5 and other fluorescent lights should be switched when the plant is 6-12 inches tall (unless you have light coming in from the sides, in which case it can be a little taller as long as all of the bud sites are getting light). Using 250W HPS, turn on the light when the plant is 12′′ tall
  • 400W HPS, turn on the light when the plant is 17′′ tall
  • 600W HPS, turn on the light when the plant is 21′′ tall. Light Emitting Diode (LEC) or Ceramic Metal Halide (CMH) Grow Lights– Follow standard rules for HPS lights according on your wattage (315W is suitable for 15′′ tall plants, and a 630W is ideal for 22′′ tall plants)
  • LED Grow Lights– LED grow lights are becoming increasingly popular. Unfortunately, the model has a significant impact on this. It’s partly a question of trial and error because there isn’t a “standard” for LED grow lights the way there is for other types of grow lights. It’s a good rule of thumb to measure the length of your major colas after switching to 12/12 (from a prior grow) and to try to start blooming with your new plants when they’re approximately that height. So, if your primary colas grow to be roughly 12 inches long, you should begin flowering when the plant is 12 inches tall, and so on. Nonetheless, if you aren’t sure about your LED setup yet, I recommend just adhering to the “half the ultimate intended height” guideline. This assures that at a minimum, the plant will fit in your grow room and that you will be able to understand what to anticipate from your LED model.

Note: Defoliation (removing leaves to expose bud sites) allows you to create larger buds at a deeper level in the plant. Provided you utilize defoliation, your light may be able to support significantly higher plants with longer buds if your light is sufficiently bright. Due to the fact that everyone’s results will be a bit different depending on their strain, environment, and personal growing tactics, it’s critical to always test your plants with your light and your setup.

“Tall” vs “Short” Strains

Despite the fact that plants normally double in height following the changeover, some strains, particularly tall and small ones, might extend more or less than the norm! Always pay attention to what the breeder tells you about your strain and make your decisions based on that information!

  • If you have a “tall” strain, begin flowering earlier than indicated (around one-third the ultimate intended height), and continue blossoming until the end of the season. When using a “short” strain, you should wait until the plant is 34 the ultimate ideal height before switching to ensure that the plant is tall enough when it has finished stretching.

Because the buds at the bottom of the photo are not contributing much weight to the plant, the farmer could have converted to 12/12 earlier without affecting output. Sativa plants of this type can quadruple in height once they reach the blooming stage, which means it’s typical to wind up with a Sativa plant that is far higher than intended!

Optimum Cannabis Height Outdoors?

Outdoor plants, which develop under the intense light of the sun, are subject to different height constraints than inside plants. In the open air, plants can continue to grow in height for as long as they receive sufficient direct sunshine each day and have adequate root area. Root area is more important outside and in soil than it is indoors or in coco or hydroponic systems. Root area for outdoor plants is typically given by large fabric pots (600 gallon containers or larger in some cases!) or by raised beds filled with rich, well-drained soil in a sunny location.

It received more than nine hours of direct sunlight every day.

So What’s theBestPlant Height?

At the end of the day, there is no “proper” or “optimal” height for a cannabis plant, and as with most things in the world of cannabis growing, it is highly dependent on your setup. I’ve provided you with some broad guidelines for what to strive for and what to expect, but it’s important to note that this is a very simplified version of the information. Unfortunately, there isn’t a singular recipe that works for every grower and every situation. However, the images that follow should provide you with some inspiration!

  • Under a 600W grow light, this marijuana plant produced remarkable yields for its size, but take note of how the buds are thick all the way down the stem.
  • In addition, there is open area behind and to the left of the facility, which is useful for parking.
  • In this case, the plant was given a “lollipop” appearance (the lower part of the plant was stripped of leaves and bud sites before being switched to the flowering stage).
  • If this plant had been permitted to preserve additional bud sites, it is likely that it would have produced even more fruit.
  • Please take note of how little the buds are at the base of the following plant.
  • A typical harvest appearance for a properly-sized plant is as follows: the top buds should be roughly twice the height of the bottom buds, with large but little buds at the bottom.
  • Here’s another example of a plant that reached a respectable height at the conclusion of its life.
  • However, you can tell where the buds finish and the thick layer of leaves begins when the thick layer of leaves begins.
  • They could have sustained a plant that was much higher if their grow light had been more powerful in that situation.
  • This plant was grown under a 1000W fluorescent light and has enormous, thick, arm-sized buds that extend almost to the base of the plant.
  • All of those colas would have been far longer, with a large number of hefty buds beneath them.

This plant should have grown around twice the height it was (and double the size of the longest cola) in order to have produced as much as it was capable of under the grow light it was provided. However, the grower still had a substantial amount of bud with which to comfort himself.

What to Remember About Plant Height

  • Prior to flowering, the ideal plant height is about equal to the length of your “main” (solid) colas. For your first few grows, you’ll have to make educated guesses (and I’ve included some tips above to assist you in getting started), but once you’ve gained some expertise with your setup, you’ll be able to dial it in flawlessly every time as long as you conduct thorough strain research first. Plant size and the number of bud sites in the vegetative stage (while maintaining the right height) can enhance the number of colas and, eventually, yields if these factors are addressed. The blooming stage is aided by training the canopy to be flat, yet wide enough to span the full region under the light
  • This ensures that every cola are a reasonable distance from the grow light
  • Allowing plants to grow to heights that exceed the capacity of your lighting can result in lost time during the vegetative period. By exposing more bud sites to light through defoliation, you can encourage the growth of larger buds lower down within the plant. As a reminder, always attempt to perform a “autopsy” after you grow and examine your photographs closely to see if there is anything you might have done differently to achieve even better outcomes! In every stage of my life, I learn something new.

With a better understanding of proper plant size and its relationship to your grow light (as well as how to determine whether you should have let your plants grow taller or shorter after the fact), I’m hoping that some of you will be able to either increase your yields by allowing your plants to reach the proper size, or save time in the vegetative stage by switching to flowering before your plants grow larger than they need to be!

P.S. One Last Thing About Plant Size…

Additionally, the total size and bulk of the plant have a significant impact on eventual yields in addition to its height. A larger plant may easily sustain a greater number of larger colas. As a result, it is preferable to increase the whole plant size rather than only its height in order to optimize yields. Plants that are wide and flat, like a table, rather than tall and narrow, are preferred. Many indoor growers allow their plants to develop in size horizontally while restricting the plants’ capacity to grow in height over the reach of the grow light’s illumination.

You should also teach your plant canopy to be flat and wide before transitioning to the flowering stage, in addition to ensuring that your plants are the right height.

Filling your grow space with colas can help you increase your yields.

  • The following factors are important: yields, bud quality, “sparkle,” THC levels, CBD levels, smell/taste, density, and more. Bonus: What Factors Influence Yields

Detailed Guide To Choosing The Right Size Grow Tent For Your Plants

Are you unsure of the size of grow tent you’ll want based on the quantity of cannabis plants you intend to cultivate? I’ve broken down all of the criteria that need to be examined so that the decision-making process will take no more than a few minutes to complete. In general, you should have 22 feet of grow area per mature cannabis plant in your grow tent, according to the American Cannabis Association. You’ll also need to make room for other products such as a humidifier. These estimations are based on the assumption that you will not train your plants.

Depending on the training technique you choose, this might result in an increase in the amount of area required per plant.

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By following the steps in this guide, you will have answers to the following questions:

  • What is the appropriate size grow tent for four plants? What size grow tent do you recommend for 8 plants? What size grow tent do you recommend for 12 plants? And so on.
  • What size grow tent should I use for autoflowers
  • What size should the grow tent be
  • How tall should it be
  • How to manage the height of your plant while it is growing in a grow tent
  • When looking for grow tents, there are a few more things to consider.

Finally, it boils down to how effectively you can utilize a particular area and whether or not you are taking efforts to guarantee that you are making the most of your space.

How many cannabis plants per grow tent?

All of these suggestions are based on the assumption that you will be planting in 3 or 5 gallon grow bags or buckets.

What size grow tent for 1 cannabis plant:

When growing one cannabis plant, I recommend a grow tent that is 24 inches by 24 inches by 48 inches.

What size grow tent for 2 cannabis plants:

In order to produce two cannabis plants, I propose a grow tent that is 24′′ x 48′′.

What size grow tent for 4 cannabis plants:

I propose a grow tent that is 48 inches by 48 inches by 80 inches in size for four plants.

What size grow tent for 6 to 8 cannabis plants:

I propose a grow tent that is 96′′x 48′′x 80′′ in size.

What size grow tent for 10 cannabis plants:

It is recommended that you purchase a grow tent that is 96 x 48 x 80 inches.

What size grow tent for 12 to 16 cannabis plants:

I propose using *two* 48′′x96′′x80 in. grow tents for a total of 12 to 16 marijuana plants.

What size grow tent for autoflowers:

Autoflowers typically reach a height of 3 feet. If you’re thinking of growing autoflowers in a grow tent, I’d recommend following the same requirements as those listed above. Here’s why: Even these autoflowers are smaller in stature, their branches may still span a significant amount of space when completely developed, despite the fact that their height is reduced. As a result, cultivating autoflowers in a grow tent will not result in significant space savings when compared to growing ordinary cannabis plants in the same space.

However, there isn’t a significant change in the quantity of room you’ll have.

I’ll outline strategies for managing the height and growth of your plants so that you can really fit this many plants into your grow tent in the sections below.

Determine the space needed per plant:

Cannabis plants may grow to a variety of sizes, many of which are within the control of the grower. Identifying how much room you’ll require for each plant is an excellent starting point for figuring how much overall area you’ll want in a grow tent or greenhouse. The three and five gallon grow bags are the most often used grow bags for cannabis cultivation at home, respectively. It is recommended to allow 2 gallons of soil for every foot of anticipated plant height as a general rule of thumb.

Grow Bag Size (Gal.) Height(cm) Diameter(cm)
1 gal. 16cm 18cm
2 gal. 20cm 22.5cm
3 gal. 23cm 27cm
5 gal. 27.5cm 31.5cm
7 gal. 29cm 36.5cm
10 gal. 31cm 40.5cm
15 gal. 33cm 46cm
20 gal. 40cm 51cm

Take a look at the diameters shown above for each of the grow bag sizes available. But you can’t stop there since the plant’s branches will eventually extend over the edge of the grow bag, requiring you to cut them back. When using 3 and 5 gallon grow bags, keep in mind that the cannabis plants can grow up to 13-15cm over the edge of the grow bag on any one side of the bag. In a 5 gallon grow bag, a mature plant is growing. Taking this into consideration, if you want to cultivate four plants in three-gallon grow bags, you need provide 44-49cm (16-17.5in) of room per plant in total.

If you want to grow in larger bags or buckets, you should anticipate that the branches may likely develop longer than the 13-15cm indicated for 3 or 5 gallon grow bags, so give your cannabis plants even more breathing room.

It is theoretically possible to cram them all into a 3x3ft grow tent, but there would be no room for a standing fan or a humidifier in such situation.

Of course, you could still hang things from the top if you wanted to. If you want a comfortable fit for four cannabis plants in 3-5 gallon grow bags (as well as a humidifier), a 44 grow tent (48′′x48′′x60′′ in.) is the best option.

How tall should my grow tent be?

You should absolutely stay with the usual 80-inch height on the 4×4 grow tents whether you’re growing cannabis or a tall vegetable plant like tomatoes. This is the reason why: Your grow light will dangle around one foot from the ceiling of the grow tent, and depending on the power of your grow light, you’ll need between 18 and 24 inches between the grow light and the plant surface of the growing environment. As a result, you’ve already utilized up 2.5-3ft of your available height. That leaves you with 3.5ft of space for your cannabis plants, maybe a bit more if you’re able to hang your grow light a little higher in the ceiling.

Using a little grow tent with a shorter height may be sufficient if you’re growing smaller plants such as succulents or house flowers in your garden.

Leave space for a humidifier in your grow tent:

Growing plants inside has several advantages, one of which is the ability to regulate the atmosphere in order to produce the finest harvest possible. It’s important to remember that while deciding on the size of your grow tent, you should choose one that has adequate space for your plants and also has a humidifier. This 6 liter humidifier is one of my favorites. The digital display that allows you to select the correct humidity level on your own so that humidity levels don’t become a guessing game is a great feature.

It will occupy an area of around 11 inches by 7 inches in your grow tent.

Side note on grow tent humidity:

When it comes to cultivating cannabis, humidity is really important. Air that is too dry can inhibit development, whereas air that is too humid will promote mold or decay. Cannabis clones require 70 percent humidity since they absorb the majority of their water through their leaves while their roots are establishing. The remaining vegetative and blooming growth cycles can be completed at humidity levels of 50 percent or higher. Because tomatoes are primarily water, if you’re cultivating tomato plants, you’ll need 70-80 percent humidity to keep them healthy.

Controlling Plant Height In Your Grow Tent:

The ability to adjust the height of your cannabis plants will be critical if you want to successfully fit four plants into a 44 grow tent. Fortunately, there are a few strategies you may use to keep the height of your cannabis plant under control.

Switch plants to flowering phase at the right time:

When your cannabis plant has grown to half the height you want it to achieve at the end of the vegetative development period, reduce the length of the lighting cycle from 18 hours to 12 hours.

The idea for this is that your plant will continue to grow the remaining 50% during the flowering cycle. This has shown to be a reliable rule of thumb, and it will assist you in growing plants that are the appropriate size for your grow tent.

Top Your Cannabis Plant:

Remove the top node of the main stem of your plant and discard it. Not only will this limit the height of the plant, but it will also allow hormones to seep downward to the bigger branches, assisting them in producing additional buds.

Low Stress Train Your Cannabis Plant (LST):

Your biggest branches should be bent over to the edge of the grow bucket and tied down in some way early on in their vegetative development. The branches will naturally bend upwards toward the light as a result of this strategy, but the eventual height of your plants will be reduced as a result. More information about LST may be found in my piece about increasing cannabis yields.

Use a smaller grow bag to grow smaller plants

In the event that you’re concerned about your cannabis plants taking up too much space within your grow tent, providing the roots a limited place to grow in might assist you limit their final growth. Instead of a 5 gallon grow bag, a 3 gallon grow bag will suffice. A 7 or 10 gallon grow bag, on the other hand, may accommodate a larger-sized plant that will take up the whole grow tent, allowing for more root development.

Do More Cannabis Plants In One Grow Tent Equal More Yields?

Trying to cram as many plants as possible into a small space will not necessarily result in higher yields. As a result of overcrowding your tent, your plants will metaphorically be fighting each other for light and CO2. In a research conducted by McGill University on cannabis yields, one of the factors cited was proper plant spacing. Without a doubt, four plants in a 4×4 foot grow tent will produce more than two or three plants in the same size grow tent. I’m referring about the attempt to overcrowd 5 or 6 adult-sized plants into a grow tent with a diameter of 4 4 feet.

The same amount of harvest from 1 to 2 plants as you would from 3 or 4 plants might result if your lighting isn’t powerful enough, so make sure your illumination is enough.

Please see my guide on optimizing yields for more information.

That’s it!

You are now completely prepared to go out and get the appropriate size grow tent to accommodate whatever number of plants that you desire. These are broad suggestions that should be sufficient for most situations. When it comes to plant space, remember that more space is always preferable if you have the financial flexibility to go one size up and give your plants a bit more breathing room. However, the final decision is entirely up to you. If you’re planning on purchasing a grow tent in the near future, be sure to read my guide on selecting the correct sized grow tent fan, as well as my guide to the best grow tents on the market!


You have complete control over the amount of space each plant takes up in your grow tent. I estimate that you’ll need 44-49cm per cannabis plant if you’re using 3 or 5 gallon grow bags.

How many cannabis plants fit in a 4×4 grow tent?

You should be able to cultivate four cannabis plants in three or five gallon grow bags, and you should have enough space to accommodate a humidifier.

How do I control cannabis plant height?

By reducing light exposure from 18 to 12 hours each day after the cannabis plant has grown to half of its target height, you may begin blooming your plant.

Do I need a humidifier for my grow tent?

Humidity is essential for producing cannabis and preventing powdery mildew, which can kill your plants if not maintained properly. Allow for additional room (about 126 inches) for a humidifier.

How High To Hang Grow Lights Above Plants – Based On Science!

The most often asked question I receive from indoor growers is how high they should position their grow light in relation to their plants. The basic answer is “it depends,” but I intend to elaborate on the various elements that influence the decision below. When growing cannabis or any other plant that produces fruit or veggies, your plants require a particular quantity of light, which means that the distance between your grow light and the plants will make a difference in how much light your plants receive.

Recommended HPS / CMH / HID Grow Light Distance From Plants at 100% Power:

Watts: Grow Light Height Above Plants:
150w: 3ft (seedling); 2ft (veg/flower)
250w: 3-3.5ft (seedling); 2.75ft – 3ft (veg/flower)
400w: 4ft (seedling); 3ft – 3.5ft (veg/flower)
600w: 4.5ft (seedling); 3 – 3.5ft (veg/flower)
1000w: 5ft (seedling); 4-4.5ft (veg/flower)

*According to Jorge Cervantes’Grower’s Bible, the recommended hanging heights are:

RecommendedLED Grow Light Distance Above Plants:

When it comes to seedling growth (the first 3 weeks), LED grow lights should be kept between 24-26 inches in height, and between 18-22 inches in height during the vegetative and blooming periods of the plant. You can hang the grow light a few inches higher if the light is particularly powerful, or a few inches lower if it is not too powerful (cost less than $130). Due to the fact that different types of LEDs are used, different magnifying lenses (or no lenses at all), and varied amounts of watts are sent via the LEDs, practically every LED grow light is unique.

It is normally possible to find the suggested LED grow light hanging heights on the manufacturer’s website, which is also usually available on the website from which you purchased the grow light.

This is based on light intensity measurements supplied by the manufacturer, and it may or may not be accurate.

Recommended T5/T8 Grow Light Distance Above Plants:

T5 and T8 bulbs have a broad range of power output, and as a result, the light intensity and the distance between the lights and the plants can vary significantly. For example, a fixture with two bulbs can produce between 60 and 100 watts of light output. A fixture with four or six bulbs, on the other hand, may provide two to three times the amount of light.

Low-power T5 and T8 grow lamp systems can be hung 6 to 10 inches above plants to provide enough illumination. Grow light systems with higher power T5/T8 bulbs can be hung 12 to 14 inches above the foliage of plants.

When Should You Adjust Your Grow Light’s Distance From Plants?

In order to accommodate your plants’ maturation and increased proximity to your grow light, you’ll need to either reduce the light or move it further away from them. If you don’t alter the distance between the plants and the grow light, you run the danger of burning them.

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Plants Look Heat Stressed:

If your plants are suffering from heat stress, you will need to raise the height of your grow light above them. In response to the extreme heat, the leaves appear to be curling upwards towards the sun. If you see this happening, increase the distance between your grow light and your plants as soon as you possibly can.

Plants are Stretched:

When the distance between the plant and the grow light is too great, the plant stems expand. To obtain more intense light, the plant deliberately expands its stalk and stems to get closer to the light source and receive more light from it. Plant stretching can be caused by genetics as well, however if you see that it is happening, you should move the grow light closer to the plants to prevent it from happening again. Keep in mind that every 12 inches closer to the grow light results in a 75 percent increase in intensity.

It is possible that you will need to top the plant if you experience substantial stretching in order to keep it from becoming too enormous.

Use The Inverse Square Law To Determine Grow Light Hang Distance Above Your Plants:

According to the inverse square rule of mathematics, a grow light’s intensity at a certain distance from a plant may be calculated. This can be used to assess if you need to move your grow light closer or further away from your plants. With regard to grow lights, the inverse square law of light applies in that when the distance between a plant and a grow light is doubled, the area covered by light grows, but the intensity of the light reduces to 25 percent of the intensity of the light at the original distance.

A quarter of the intensity at 4 meters is equal to a quarter of the intensity at 2 meters This will remain true for the intensity of your grow light at various distances, such as 6 to 12 inches, 12 to 24 inches, 24 to 48 inches, and so forth.

Starting at one foot, the intensity increases to 25 percent at two feet and 11 percent at three feet if the distance is increased by one foot.


In order to determine another intensity reading at a different distance, you simply need to know one intensity reading at a different distance. Assume that the maker of your grow light claims that your grow light emits 1000 micromoles of light at an 18-inch height above the plants. You’re aware that 250 micromoles is a more acceptable intensity for your seedlings’ growth. Based on the rule of inverse squares, you would then increase your hang height from 18 to 36 inches, and the light intensity would be reduced to 25 percent (250 micromoles) of the original 1000 micromoles, for a total of 1000 micromoles.

According to the mathematical formula, intensity = light output divided by distance2.

Answer These Questions To Determine A Proper Grow Light Hang Height:

There are a few key questions to address in order to determine the appropriate grow light height for your grow area if you don’t want to rely on the inverse squares rule or the manufacturer’s suggested height for your grow lights. You must Measure, Convert, and Compare in order to be successful.

What amount of light intensity do your plants receive at each height?

You must first determine (approximately) how much light your plants are receiving and then compare that figure to the amount of light they should be receiving. Most manufacturers give light intensity data at a few relevant heights above plants, which are usually sufficient for most applications. If you are unable to locate these manufacturer-provided light intensity values, you can purchase a lux or PAR meter and conduct your own tests. Lux meters, in contrast to PAR meters, are fairly affordable.

A Lux meter should be purchased to determine how much light your plants are receiving at their current distance from your grow light.

Insert the amount of Lux, then pick Red + Blue + White LED from the drop-down menu, and then push the calculate button.

“Can you tell me how many micromoles of light cannabis plants require during each of their growth phases?”

  • For example, plants in the seedling phase require between 200 and 300 uMol/second, while plants in the vegetative phase, receiving 18 hours of light, require between 306 and 617 uMol/second, and plants in the flowering phase, receiving 12 hours of light, require somewhere in the neighborhood of 460 and 925 uMol/second.

The height of your grow lamp does not need to be adjusted if your plants are currently getting light intensity that falls within the range described above. Moving the grow light closer to the plants would be necessary if the temperature fell below this range. Moving the grow light further away from the plants would be necessary if the plants were to grow over this range. Keep in mind that more light intensity equals better yields. To learn more about photoperiodic flowering time (PPFD) and the light intensity levels necessary to cultivate cannabis, check out my comprehensive post on the subject here.

For CMH and HPS Grow Lights:

People who use CMH or HPS grow lights frequently question me about Lux and what level of Lux intensity is best for their plants. Here is my recommendation for those who are utilizing CMH or HPS grow lights: Purchase aLux meter and use it to determine how much light the plants are receiving at each height of the plant. Once you have converted your Lux reading to micromoles, you may move on to the next step. Thanks to Apogee Instruments, the maker of the light intensity meter, a conversion table for converting Lux to micromoles has been constructed and made available.

That is more or less in line with what cannabis plants require in order to thrive.

Whenever the number of moles is close to or below 20, you should lower the lamp until it is close to or below 40 moles.

(Your Lux reading *.013 Lux to PPFD conversion rate * 60 seconds in one minute * 60 minutes per hour * hours in your light cycle = Moles of light per day. Is the light intensity of your CMH or HPS grow lights within this range?

  • For example, plants in the seedling phase require between 200 and 300 uMol/second, while plants in the vegetative phase, receiving 18 hours of light, require between 306 and 617 uMol/second, and plants in the flowering phase, receiving 12 hours of light, require somewhere in the neighborhood of 460 and 925 uMol/second.

The height of your grow lamp does not need to be adjusted if your plants are currently getting light intensity that falls within the range described above. Moving the grow light closer to the plants would be necessary if the temperature fell below this range. Moving the grow light further away from the plants would be necessary if the plants were to grow over this range. Keep in mind that more light intensity equals better yields. To learn more about photoperiodic flowering time (PPFD) and the light intensity levels necessary to cultivate cannabis, check out my comprehensive post on the subject here.

It would be possible to advise everyone to hang their grow light “xx inches away from the plants” if every grow light was exactly the same.

However, there are two additional questions that must be answered in order to decide the appropriate height for your grow light.

Is your grow light dimmable?

In some cases, if your grow light is dimmable, you may be able to dim it instead of altering the distance between the grow light and your plants. Having aLux meter accessible is, once again, the most important part of this entire procedure since it allows you to accurately measure, convert, and compare the light intensity levels to the real light intensity levels your plants require to develop. In most cases, if your grow lamp is dimmable, you can alter the light intensity by turning a screw or turning a knob on the ballasts.

Another Video About Grow Light Hang Height:

The EASIEST METHOD FOR DETERMINING THE HEIGHT OF A GROW LIGHT! Cannabis Grow Light Hang Height – LEDHPS Grow Light Hang Height Recommendations Wishing you the best of luck! Would you want to learn more about home gardening? Check out my Cannabis Watering Guide, as well as my articles on how to calculate grow light coverage and how to reduce the temperature in your grow tent.


The appropriate height for your grow light is determined by the strength of your grow light. It is necessary to place a low-power grow light closer to the plants than a high-power grow light. The stage of development of the plant is also important. In general, LED grow lights may be placed anywhere between 16 and 24 inches above the ground. HPS lights must be suspended at a height of 36 to 48 inches, depending on their power output.

Do I need to adjust grow light height as plant grows?

Yes, as the plant goes closer to the light, the intensity of the light increases, and you run the risk of burning the plant if you don’t change the height of the grow light. References:

My Cannabis Plants Are Growing Too Tall: What Should I Do? – RQS Blog

Is your cannabis plant getting too big? There are several reasons why stretchy, spindly plants may be a pain. Plants with uncontrolled growth can cause a variety of problems, including toppling over and burning themselves on your lighting equipment. A taller plant, on the other hand, does not necessarily translate into a larger crop. Growing tall cannabis plants might be an indication that they are unhappy, and this is especially true if they are not receiving enough light. Apart from stretching your plants, a lack of light will have a detrimental influence on the amount and quality of your final harvest.

So, how can you prevent weed plants from growing to excessive heights? There are a plethora of solutions available to you, and some will even assist you in increasing your yield!

Why Should You Stop a Cannabis Plant From Growing Too Tall?

There are a slew of compelling arguments for keeping cannabis plants from growing to excessive heights. Whether you’re trying to maximize the potential of a grow place or keep the grow hidden, you need to make sure your plants aren’t allowed to develop unchecked and unattended. Here are various justifications for controlling the development of a marijuana plant:

Privacy and security
Big plants will attract more attention—both through size and smell.
Flowering stretch
Some plants can double in size during the early flowering stage. If you haven’t prepared for this, you might discover you don’t have enough room in your grow space.
Equal light distribution
Taller plants will get a lot of light at the canopy, but very little near the base. This means that the lower buds will hardly develop, reducing your yield potential.
Get light to smaller plants
If you’re growing multiple strains, some will be smaller than others. Unless you control the height of the taller ones, they will stop the smaller plants from getting enough light.
Prevent light burn
If your plants grow too tall and get too close to the lights, they will burn. This can hamper overall growth and will ruin the main colas at the top.

Why Is My Cannabis Plant Growing Tall and Skinny?

If your weed plants are growing too tall, one of the first steps you should take is to determine why this is occurring. Otherwise, you risk using the incorrect solution, which will have a detrimental influence on your plant’s growth. The following are examples of reasons why your weed plants may be growing excessively tall:

Incorrect light distance
If your lights are too far away from your plants, they will stretch in an attempt to get closer. This is a natural behaviour born of trying to grow above competing plant life.
Weak light
If your lights are just not strong enough, your plants will stretch up to them no matter how high or low they’re placed—they will hunt for light until they’re satisfied.
Red-dominant light spectrum
In nature, cannabis plants grow during the spring and summer. At these times, when the sunlight is at its strongest, plants are subject to blue and white light spectrums. During autumn, the sunlight weakens and enters a red spectrum. To give your plants ample photo-fuel, make sure you’re using the right light spectrum for the respective stage of development.
You’ve kept them vegging too long
Photoperiod cannabis plants kept in the vegetative stage will continue to grow. So if you veg them for too long and don’t control it, they will grow very large and unwieldy.
Some strains of cannabis like to grow tall and spindly—for instance, landrace sativas. While these can be controlled, if you’re really limited for height, many indica varieties are more suitable.
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How To Control a Cannabis Plant’s Height in the Vegetative Stage

The vegetative stage is often the most advantageous stage for controlling the growth of your plant. In this case, you may afford to cause it harm, as long as you see a noticeable difference before it begins to blossom. Damage, on the other hand, may only result in a reduction in yield during the blooming period. So don’t put it off any longer!

Bending or Low-Stress Training

When it comes to controlling your plant’s development, the vegetative stage is usually the most beneficial. In this case, you may afford to cause it harm, as long as you see a noticeable difference before it begins to bloom. While the plant is in the flowering stage, damage may only result in a reduction in the amount of fruit produced. Don’t put it off any longer!


This is a more aggressive way of training than the previous one. When you top a plant, you are physically taking off the top of the plant, which is where the main cola would start growing. The plant rebounds as a result of this by producing not one, but two new major colas in its place. These have a tendency to spread outward rather than develop upward. So, once again, not only do you have control over the height of the plant, but you also receive additional bud! Remember to do this at the vegetative stage, or else you’ll be cutting off your primary bud!


Using the screen of green (ScrOG)method, you may grow your plants via a mesh screen while securing them in place. As a result, instead of continuing to develop upward, they begin to spread outward. Once again, this strategy maximizes the amount of light that reaches the surface area.

Pre-Flowering Topping

Allowing your plants to grow unchecked throughout the vegetative period, then topping them shortly before flowering, will also help you regulate their overall height. When your plants are about to enter the blooming stage, prune all of the branches off the main stems. Consequently, the blooming reach is curtailed, and the plants are encouraged to create new flower growth rather than concentrating their energies on extending out farther. Pre-flowertopping may necessitate a full pre-flower pruning session on occasion.

It is past time to take severe measures.

Don’t be concerned; cannabis is a tough plant that can even survive being reduced to a stalk with only one or two leaves left.

Try not to be too hard on yourself for losing valuable time and producing lower-than-expected results. On the road to becoming an expert in weed growth, any and all learning will be beneficial.

Move Tall Plants to the Edges

Alternatively, if you have left it too late and parts of your plants have stretched, you may just want to shift them to avoid light burn. Because the intensity of the light is greatest in the centre, moving the plants to the side will reduce the likelihood that they will be burned by the light. Furthermore, because smaller plants will receive more light, they will be less inclined to stretch. One thing to keep in mind, though, is that if the taller plants are already strained, shifting them out of the most intense light may just serve to worsen the situation.

How To Control Height in the Flowering Stage

Ideally, you’ll notice that your cannabis plant is growing too tall during the vegetative stage, and you’ll take action to correct the situation at that point. However, life is not always perfect! As previously stated, certain strains can double in size during the early blooming period, and others do not alter in size at all at this time. Growing a certain strain for the first time might make it difficult to determine whether it will expand during the blooming process. As a result, you can find yourself with an overflowing grow space and in desperate need of a solution.

Raise Grow Lights As High as Possible

At this point, your alternatives are limited, and it is likely that your upward rise will come to a stop shortly. Keeping this in mind, one of your greatest solutions may be to raise the brightness of your lights and just prevent light burn as much as you possibly can. Flowers will not be produced by plants until the end of their blossoming period. This, however, may not be achievable depending on the size of your grow space.

Reduce the Number of Light Hours per Day

Plants require light in order to grow (you probably know this). As a result, lowering the amount of light that a plant receives will diminish its potential to grow. You don’t want to lower it too much since doing so would result in the crop being ruined. Reduced sleep time, even as low as 11 or even 10 hours per day, should help to reduce stretching at this stage.

Lollipop Your Plants

Lollipopping is one of the few training procedures that may be performed during the blooming stage of a plant’s life cycle. Not only will it prevent your plant from growing too tall, but it will also minimize humidity and the likelihood of mould developing, as well as increasing your yield, if done correctly. Just keep in mind that if you’re using it to limit growth, you must use it before to stretching to get the best results. Once something has happened, it is impossible to undo it. Remove all of the plant’s lower growth in order to make a lollipop.

In reality, lower leaves of cannabis plants that are consuming more energy than they are generating are naturally lost by the plant.

Progressive Harvest

Training with lollipop sticks is one of the few strategies available for usage during the blooming stage of a plant’s growth cycle. Not only will it prevent your plant from growing to an excessive height, but it will also minimize humidity and the likelihood of mould, as well as increasing your yield, if done correctly. Just keep in mind that if you’re using it to restrict growth, you must use it before to stretching to ensure that it works. Once something has occurred, it is not possible to undo the situation.

In spite of the fact that you may believe everything is valuable, the leaves and buds at the bottom of the plant will receive little light but will nevertheless consume the plant’s resources.

In reality, lower leaves of cannabis plants that are consuming more energy than they are generating are naturally lost by the plants. Simply said, this is speeding up the procedure.

Turn Down Light Intensity

Lollipopping is one of the few training procedures that may be performed during the blooming stage of the plant’s life cycle. Not only will it prevent your plant from growing too tall, but it will also reduce humidity and the likelihood of mould developing, as well as increasing your output. It’s important to remember that if you’re using it to limit growth, it has to be done before stretching. Once something has occurred, it is impossible to undo it. To make a lollipop, remove all of the plant’s bottom growth.

In reality, lower leaves of cannabis plants that are consuming more energy than they are generating are naturally removed.

Supercropping During Flowering

This is a desperate approach that should only be used as a last resort in extreme circumstances. During the flowering period of your plant, it is necessary to dramatically bend the tallest branch of your plant. Your plant will use energy in order to restore that portion, which might be damaging to the general health of the plant. However, if it gets to this point, it’s time to start thinking about damage control. Remember that if you left them on, you would most certainly fry your plant, so don’t get too worked up over what may have been!

Too-Tall Cannabis Plants: Learn From Your Mistakes

Every grow is a major learning experience, and as long as you take note of what went wrong, there’s no damage in failing to learn from your mistakes. In reality, as long as we pay attention, there is no such thing as a failure. How can we avoid stretched and unnecessarily tall plants in the future, bearing this in mind?

Use Smaller Pots

The maximum size of a plant is partially determined by the size of the pot in which it is grown. The root system of a plant increases in proportion to the size of the plant. To prevent your crops from growing too tall in the future, lower the size of your containers. This should prevent them from growing too tall. Most advantageous about this alternative is that it does not require any involvement throughout the growing process and presents no damage to the health of your plants (as long as the pots aren’t too tiny).

Keep Grow Lights at the Optimal Distance

Maintaining the proper distance between your grow lights and your crop will prevent them from stretching, which is especially important during the vegetative stage. Ideally, you want them to be as near to each other as possible without causing mild burn. Remember to raise the lights as the plants develop to ensure that they are properly lit.

Consider the Type of Light

Different forms of light have varying amounts of power and are classified according to their wavelengths.

Plants that are exposed to the appropriate strength and spectrum of light are more likely to grow thick and robust rather than reaching for the sky in quest of light.

Research Your Strains

If you buy a commercial cannabis seed or know what strain you’re growing, there will be information accessible regarding normal heights—both inside and outdoors—if you research the strain you’re cultivating. This will tell you how tall a plant will grow if it is cultivated in the best possible environment. If the average height of a plant appears to be pushing the boundaries of your grow, try selecting a smaller specimen to allow you some wiggle room in case the plant starts to expand. In general, indicas have a low and bushy growth pattern, whereas sativas have a tall and spindly growth pattern.

Don’t Wait Too Long To Flower

As previously said, the longer you let the plant to mature, the higher it will get. As a result, make the changeover at the appropriate moment. If it does become too large, prune it back, allow it to heal, and then turn it to blooming mode. While you’re still in the vegetative state, you have a lot of freedom to do anything you want. Due to the fact that plants can double in size during early blooming, check the maximum height indicated for the strain and begin flowering when the plant is half the listed maximum height.

Consider Growing in a Taller Grow Space

This is a luxury that many people cannot afford. If, on the other hand, your crop grew to be too large for your grow area the previous time, try using a larger place the following time. Having additional room will not only allow for more stretching, but it will also aid in ventilation, increasing the likelihood of a healthy harvest.

Important Considerations for Tall Cannabis Plants Indoors

When plants grow to be too tall inside, there are two primary things to keep an eye out for.


Cannabis produces a significant amount of water through its leaves. Marijuana thrives in environments with relative humidity (RH) ranging from 50 to 65 percent. When they grow to be too large, humidity can become a concern due to the continual release of water vapor into the air by the plants. Water then collects on the leaves and other surfaces in the grow room, where it can lead to the growth of mould and other problems. If excessive humidity is becoming an issue, a dehumidifier or raising the power of the exhaust fan may be necessary.

Only the lower and mid-level fan leaves should be removed.


When plants develop to an excessive size, the temperature in the grow-op might rise, just as it does with humidity. Reduced airflow and excessive height can cause temperatures to rise, and plants can be placed too near to grow lights as a result. When the temperature averages 25°C, cannabis grows at its best. When temperatures rise over this threshold, plants are more likely to stretch. High temperatures can also have an impact on the production of leaves and flowers, as well as the flavor and potency of the finished buds.

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