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How to Prevent and Fix Stretching in Cannabis Seedlings

Long, stretchy stems are one of the most common problems growers face during the seedling stage. Luckily, there are a few simple ways to prevent and fix stretching in cannabis seedlings.

Fix stretching in cannabis seedlings, and prevent it from happening again.

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Just like baby humans, cannabis seedlings are super fragile and need plenty of tender loving care to flourish. Unfortunately, many growers run into the same issue during the early stages of their cannabis plants’ lives; their seedlings grow long, stretchy, and weak stems. This, in turn, can lead to a host of issues that put your crop at risk of delivering subpar results.

Below, you’ll learn how to prevent and fix stretching in cannabis seedlings.

Understanding the Seedling Phase

Seeds are like little genetic time-capsule bombs. What this means is that they only have one job, and only get one chance to pull it off. They are pre-programmed to survive. A seed self-contains absolutely everything a future plant needs to get started. Once activated with moisture and darkness, it will trigger germination, and once that gets going, there is no turning back.

A seedling does not need any food for the first good few days of its life. From its genetics, it is already backpacking all the essential nutrients needed to embrace the miracle of life. Seedlings have a little reserve to help establish themselves in their growing environment.

In optimal conditions, the seed shell, or husk, will crack open and a taproot will pop out, immediately digging further down in search of a water lifeline. Soon, you will see a sprout rise from the under the soil, spread out its first baby leaves (cotyledons), and then you will start noticing the first set of true leaves. Leaves have an equally important job as the taproot, but they are in search of another food source – light. Quite literally, a plant uses light to digest what it brings up from the soil.

Easy Start

The Perfect Light Conditions for Cannabis Seedlings

To grow healthy seedlings, it’s important to give them the right amount and type of light as soon as they break out of their shells. Cannabis seedlings like to receive around 16 hours of light per day at an intensity of 375 lumens and 4000 lux.

To meet these requirements, we recommend using one 12W CFL bulb per 1–2 seedlings. Keep the bulb 5–7.5cm (2–3in) from the top of the seedlings and monitor their growth carefully, making sure the plants don’t make contact with the bulbs.

Growing your seedlings under lights with a high percentage of red light may cause them to stretch. Blue light, on the other hand, helps to keep internodal spacing to a minimum and encourages plants to grow nice and stocky from the get-go.

What Causes Abnormal Stretching?

Abnormal stretching in the seedling phase is a sign of stress. By far, the most common situation that causes seedlings to stretch and topple over is light deprivation.

In the same way taproots dig for water and nutrients, the top part of the plant will stretch vigorously if it’s not receiving enough light. It’s a survival mechanism in which a plant uses up all its stored energy to rise above competing flora. In the case of indoor growing, there is no competition, but the seedling will perceive it this way. For instance, leaving the pot under a windowsill in the shade will likely trigger this behaviour. Things can get even more dramatic under artificial light.

This may seem a bit confusing for new indoor growers, as they may think they are providing more than enough light to their plants. But consider the following: Positioning a 200W metal halide (MH) bulb relatively far from the pot will be less effective than a 20W CFL bulb placed a few inches from the leaf surface. Even though CFLs are much weaker than MH, light intensity drops significantly the further away plants are from the source.

Moreover, seedlings have very small, and few, leaves. The total surface area available to absorb light is very small. So, in essence, that 200W bulb will be radiating over a very large area, but the seedling can only use a minute fraction of it. The CFL positioned right over the plant, on the other hand, will be able to give most of its 20W directly.

Other Potential Causes of Stretchy Cannabis Seedlings

Besides light deprivation, there are a handful of other factors that could be causing your cannabis seedlings to stretch. One common cause of leggy seedlings is poor nutrient content in the soil.

More precisely, cannabis seedlings benefit from nitrate-derived nitrogen. Unlike ammoniacal nitrogen, nitrate-nitrogen is a lot easier for plants to absorb and fuels shorter, bushier vegetative growth. If your seedlings are stretching despite ideal light conditions, we highly recommend checking the ammoniacal nitrogen content in your soil and fertiliser.

Another cause of leggy seedlings is heat.

While cannabis seedlings like warm, humid conditions, too much heat can cause a plant’s leaves to grow slower than its stem, resulting in tall and stretchy growth. To promote healthy seedling growth, we recommend keeping the temperatures in your grow room or dome at 19–20°C during the day and roughly 13°C at night.

Finally, cannabis seedlings can also stretch if they’re receiving too much or not enough light per day.

While some growers opt to keep their seedlings under 24 hours of light per day, we recommend sticking to 16 hours. Seedlings are fragile, and giving them too much light can cause stress and stretching. Remember, those dark hours are just as important for your young plants to develop healthy roots and respire.

How to Keep Cannabis Seedlings From Stretching and Falling Over

Stretchy cannabis seedlings can be a pain to handle and transplant. Their stems can be very fragile, and once they start vegging, their foliage can be off-centre due to the weird stretch they underwent as seedlings.

For best results, we recommend replanting your stretching seedlings deeper into their soil, correcting your lighting, and checking the nitrogen levels in your soil and/or fertilisers (as mentioned above). Once you’re confident you’ve created the right environment for your seedlings, pop them back under their lights and monitor their growth. Over time, the buried overgrown stem should sprout roots.

If possible, you may want to consider growing your seedlings outdoors under direct sunlight. There is simply no substitute for Mother Nature, and seedlings in direct sunlight will grow healthy, strong stems with short internodes. Once your plants have developed 2–3 mature leaves, feel free to move them indoors, making sure to keep their lights at the right height to prevent any further stretching.

If you have to grow your seedlings indoors, use the setup described above to ensure they get enough direct light at the right intensity.

Soon, you should notice your seedlings developing healthier growth. Short internodes and compact, green foliage are all signs that your seedlings are growing perfectly.

Note: Some growers try tying their stretchy seedlings to a stake. We do not recommend this method, as it doesn’t do anything to combat the weak, overgrown stem or the difficulty it’ll present further along in the grow.

Thinning Your Cannabis Seedling Crop to Prevent Stretching

Thinning is a common agricultural technique that’s often forgotten among cannabis growers. As the name suggests, thinning is all about reducing competition among your plants by “thinning” out the population.

Cannabis plants grow very quickly and will naturally compete with one another for space, light, and nutrients. So, while you may have been taught to think that more plants will naturally translate into bigger, better harvests—that might not be the case. In fact, many experienced growers opt to cull their weakest seedlings and only grow those plants that show the healthiest growth. This way, they focus their efforts on the plants most likely to produce the best flowers.

Thinning also helps growers maintain an even canopy across their grow room, which makes better use of a limited amount of light and space. Finally, thinning can help you avoid pests and other plagues, as you’ll be less likely to end up with a crowded grow space.

To thin your plants, simply keep a close eye on your seedlings throughout the first 1–2 weeks of their life, and only keep those specimens that show the healthiest, fastest growth.

Are your cannabis seedlings growing long, stretchy stems? Here's how to prevent and fix stretching during the cannabis seedling stage.

Why Is My Weed Plant Growing Tall And Skinny

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Growing weed is a whole lot of fun and it is very rewarding in the end too, at least if you do it the right way. However, growing pot is not the easiest thing in the world, as there are many factors to consider, and many parameters to keep at certain levels. One thing which can happen to novice weed growers is that their weed plants get too tall and skinny. Why is my weed plant growing tall and skinny? (it’s well worth picking up this FREE grow bible, it has some great information).

Well, there are a number of reasons why your marijuana plant may be growing very tall and skinny, and yes, this can quickly become an issue. It could be the strain of weed itself, you left it in the vegetative state for too long, and it can be an issue with the lights as well, both in terms of grow light distance from the plant and the amount of light your plant is getting.

At any rate, let’s go over the various causes, problems, and solutions to this issue of marijuana plants growing too tall and skinny.

Why Is My Weed Plant Growing So Tall?

There is not simple answer to this question, at least not from our end. It’s always hard to judge why a problem like this occurs when we cannot see it firsthand.

However, there are various causes and reasons as to why your weed plant is growing so tall and skinny. Let’s talk about the most common causes right now.

1. It Could Just Be The Specific Marijuana Strain

Yes, sometimes the problem can be as simple as the strain of marijuana you are trying to grow. Sure, some weed plants can grow really tall due to other issues, such as with lighting or the amount of time you let it veg for. However, there are also just some marijuana strains that naturally grow tall and skinny.

If you have a small grow space that is not very tall, you will want to avoid certain marijuana plant strains which are known for growing really tall. Not all of them have skinny stems when they get very tall, but many do. (we have covered 5 good tips to make your plant more bushy over at this article).

Here are some of the weed strains which grow really tall, which you might want to avoid, depending on your situation.

  • Agent Orange
  • Amnesia Haze
  • Bergman’s Gold Leaf
  • Blueberry
  • Bruce Banner
  • California Dream
  • Cheese
  • Crystal
  • Durban Poison
  • Gorilla Glue
  • Green Crack
  • Jack Herer
  • L.A Confidential
  • Maui Wowie
  • NYC Diesel
  • Pineapple Haze
  • Sour Diesel
  • Strawberry Cough
  • Super Lemon Haze
  • Super Skunk
  • Trainwreck

2. You Let It Veg For Too Long

Another reason why your weed plant may be growing too tall and skinny is because you left it in the vegetative state for too long. If you did not already know, the vegetative state is all about getting height.

Yes, weed plants do grow in width a little bit during this stage, but it is also when they get quite tall. Ideally, your weed plant should get about half of its height during the vegetative state. Do some research on the specific strain you are growing and for how long you keep it in the vegetative stage for.

Now, this problem relates more to a weed plant that grows too tall, but it may not necessarily lead to a thin stalk, but it definitely can. If you want to ensure that your weed plant does not grow way too tall, and potentially have a stem that is too weak and skinny to support the plant, be sure to leave it in the vegetative state only for as long as is necessary.

Sure, if you have a very tall grow space, you can let it get a bit taller than you usually would, but you do run the risk of the main stalk being too skinny to support ideal growth.

3. You Have The Lights Too Far Away From The Weed Plants

Another reason why your weed plant might be growing too tall and skinny is because you have the lights too far away from the plants. This tends to be a problem with LED lights (if you need some points on what kind of light you should use, then checkout this article).

HID grow lights with cooling systems, and fluorescent lights do not get all that hot, so this tends to not be a huge issue with those kinds of grow lights. However, LED lights have a tendency to burn your leaves and buds, and this means that they need to be kept far away from your weed plants.

Some LED lights may need to be kept up to 30 inches away from your plants, or at least 18 inches depending on the strength of the bulb. Having grow lights that are too far away from your marijuana plant, especially if the LED light is not very strong, will cause them to stretch out in order to get closer to the light and to get more light.

This will result in a stretched stalk that is tall, skinny, and usually quite weak.

4. Your Cannabis Plant Is Not Getting Enough Light

The other and one of the most common reasons why your weed plant is growing so tall and skinny is because it is just not getting enough light. If you are using a light bulb or grow light that does not put out enough watts and lumens to support plant growth, your weed plant will get strained. It will do everything it can to get closer to the light, so it can absorb more of those light rays.

This will also result in a weed plant that is tall and skinny. This tends to be a problem with fluorescent lights more than anything else. Fluorescent lights are not very strong in terms of their output, and are known for producing the lowest yields out of all types of grow lights.

If you are using a weak fluorescent light, your marijuana plant is going to stretch and get skinny so it can absorb as much light as possible.

Here is a good guide on the right light schedules to use.

5. Too Much Light From The Top & Not Enough From The Sides

Another issue which could be causing your weed plant to get too tall and skinny, instead of growing outwards too, is that you have all the light directed at your plants from the top. This is not always an issue, but it certainly can be.

This is why grow rooms need to be outfitted with reflective materials, and it is why grow tents come outfitted with reflective materials already (if you need some tent suggestions, see our buyers guide).

Reflective materials allow the light coming from the top to be reflected, intensified, and directed at your weed plants from the sides. Weed plants, and all plants in general, will grow to wherever the light is coming from.

So, if you do not have any light being reflected from the sides, or any light bulbs on the sides of your grow room or grow tent, the plant will have no choice but to grow upwards towards the light.

The problem could be that you have no lights on the sides of the room, or that you do not have enough reflective materials put up.

Problems With Weed Plants Being Too Tall & Skinny

Yes, there are a number of issues that can and often will arise if your marijuana plants get too tall and too skinny. What are the problems that occur when weed plants get too tall and skinny?

1. The Stem Gets Too Weak

One of the biggest issues that tends to arise from an exceedingly tall and skinny marijuana plant is that the main stalk becomes too weak to support the whole plant. During the seedling stage, you might notice that the whole plant more or less falls over and hits the ground, and yes, this is a problem.

Also, during the vegetative and flowering stages, especially when larger buds start to form, your plant will become top heavy, and all of the branches will become heavy with flowering buds.

Simply put, the main stalk of the weed plant will not be able to support the tall plant and all of the buds which are growing. It may bend, hit the walls, fall over, or end up on the ground, none of which are ideal or desirable in the least. It’s a pretty big problem if any of these things happen.

2. Issues With Nutrients

Another issue that may arise due to your weed plant being too tall and skinny is that it will not be able to properly absorb, process, and direct nutrients towards the buds. Yes, weed plants need certain amounts of various nutrients (we have covered Nutrients in more detail here).

The taller and skinnier your weed plant gets, the more effort and nutrients the weed plant is going to use simply to stay upright.

The more energy it has to use, and the more nutrients are wasted, just to stay upright, the less energy and nutrients are available for proper growth, especially when it comes to developing buds and THC crystals.

However, you cannot just feed it twice the nutrients, as you will cause nutrient burn. The end result is a subpar end product that is not nearly as potent as it could have otherwise been.

3. You Will Run Out Of Space

Another problem that you may be faced with due to a marijuana plant that is too tall is simply that you will run out of space. You might not have a huge grow room, so this can definitely be an issue.

If you run out of space, your weed plants start getting super close to the lights, or even touching them, there are some other issues that can occur.

Mainly, other than literally running out of space and having to do a big pruning job, your plants can start hitting the lights, which then results in burned leaves and buds, which in the end, may just ruin the crop or even severely cripple the pot plants altogether.

4. You Can End Up Burning Your Plants With The Lights

We just touched on this above, but if you start running out of space, especially if you have LED or HID lights, your plants will get too close to the lights, or even touch them.

You may be tempted to let this continue, but it is very bad. Your weed plants, especially at the top, will get way too hot and they can burn.

It’s an issue because you cannot just remove lights, as of course, your pot plants need lights, but on the other hand, if you leave the lights in, especially at the distance from the plants which they are at, and the intensity which they are putting out, you will burn and cripple your plant.

It is essential to deal with this problem of skinny and tall weed plants well before any of these issues come to full fruition.

5. Humidity & Temperature Issues

There are also issues that will arise with temperature and humidity. For one, if your plants are exceedingly tall, they will absorb, hold, and give off heat. At the same time, they also block proper airflow and ventilation.

The result is often that the temperature in the grow room is driven up. Yes, weed plants need a specific temperature for ideal growth, so this is an issue.

Related to this, as temperature rises due to tall weed plants, most likely, so will the humidity. The taller your plant is, and the more plant matter in the grow room, the more moisture and humidity the plants will create in the grow room.

Having a humidity level that is too high is a problem, a big problem. It can cause a wide variety of issues, something you can find out more about in our article about the proper temperature and humidity to grow weed in.

Here is a helpful guide on the right temp and humidity for cannabis.

How To Deal With Tall Plants & Stop Them From Getting Too Tall

Ok, so now we have figured out why your weed plants are growing too tall and skinny. We have also figured out which problems can occur when this happens, and yes, they are some pretty severe issues. However, luckily, there are quite a few solutions here.

How to deal with super tall weed plants, and how to stop them from getting so tall in the first place, is what we are going to talk about right now.

1. Choose A Short Marijuana Plant Strain

One good way to ensure that you do not end up with a super tall weed plant is to avoid the strains which we discussed above in the first section, the weed plant strains which tend to grow quite tall.

Generally speaking, cannabis Sativa is the type of weed which grows very tall. Indica strains and many hybrids tend to be stalky and a bit shorter than Sativa strains. Moreover, autoflowering weed plants usually never get very tall either (more on autoflowering vs photoperiod plants here).

2. Bending & Low Stress Training

LST or low stress training is a good way to stop your weed plants from growing too tall and skinny. Now, you do have to be careful here, because this involves tying the branches together in such a way, and tying the main stalk down, so that the plant does not get too tall.

It can be dangerous because if you bend the branches or the main stalk too far, you can end up damaging things, or even snapping the stalk clean in half.

Doing low stress training with your weed plant will not only keep it from growing too tall, by tying the branches and stalks down, but it also helps create more width, a wider canopy, and it allows for more light exposure.

It can be dangerous due to stems snapping, but that is why it is called low stress training, because you only bend them a little bit at a time, let them adjust, and then tighten the ties a bit more. It’s all about a slow long game here.

3. Don’t Keep It In The Vegetative State For Too Long

Another good way to stop your weed plants from growing too tall and skinny is to not let them vegetate for way too long. You need to look up how long a weed plant needs to vegetate for. Some people leave their weed plants in the vegetative state for up to 10 weeks or more.

Sure, this does result in a large plant with lots of branches and leaves, and if done properly, it can still have a thick stalk that will support the whole plant.

However, simply put, the longer you let your weed plant vegetate for, the larger it is going to get. Depending on the weed strain, you may only have to let it vegetate for 3 weeks.

Whatever the case may be, if you are worried about your weed plant getting too tall, it is best to be a bit conservative in terms of how long you let the pot plant vegetate for.

4. Keeping The Grow Lights At The Correct Distance From The Plants

Yet another good preventative measure to stop your weed plants from growing too tall and skinny is to keep the lights at the proper distance from the plants.

As we mentioned up above, if your weed plants are not getting enough light, or if the light source is too far away from the pot plant, it will stretch out, get tall and skinny, all in the effort to get more light. Therefore, to stop your weed plant from stretching, you need to keep the grow lights at the proper distance from the plants.

This can be a problem with LED lights, as sometimes they need to be kept up to 30 inches away from the plants, but if they get too close, they might burn the plants.

If using LED lights, they need to be strong enough so that they supply your plant with enough light from afar, without having to move them closer and risk burning, while also not being so weak that the pot plant is forced to stretch towards them.

Knowing how far from your plants the different types of grow lights need to be can make all of the difference here.

5. Using The Right Grow Lights For Your Space

Closely related to our last point, using the right type of grow lights can help to mitigate this issue of super tall and skinny weed plants. Generally speaking, your best bet is to use a high intensity HID grow low.

Keep in mind that HID lights put out the most lumens and light force when compared to LED and fluorescent lights. In all reality, while HID lights are very expensive and require a fairly extensive setup, they are by far the best options to go with to avoid tall and skinny plants.

For one, they are more than strong enough, especially if you get a big and powerful one, so your plants will get enough light and will not stretch to get more of it. Using the right grow lights for your space can make all of the difference.

You do not necessarily have to use an HID grow light, but if you are not, you want to ensure that your fluorescent bulbs or LED lights have enough light output to keep the pot plants satisfied without causing them to stretch towards the lights.

The solution could be as simple as getting stronger bulbs, or just more of them.

6. Use A Big Grow Space

Ok, so it might not take a genius to figure out that a larger grow room will help mitigate this problem.

What you need to keep in mind here is that a larger grow room, specifically a taller one, will stop you from running out of space and clearance, and if using LED lights, will allow the plants to grow tall without getting too close to the lights.

However, this may not solve the problem of a weak center stalk. Yet, having a large grow space is better than a small and cramped space either way.

7. Pruning & Trimming Your Weed Plant

If your weed plants have already gotten too tall, one of the only viable solutions may be to do a pre-flowering stage trimming and pruning job.

If the cannabis plants have already taken up most of the space in your grow room before you have begun flowering, there is no point in starting the flowering stage as is, because the plants will not have enough room for the flowering stage.

Remember guys, a marijuana plant can as much as double in height during the flowering stage.

Therefore, the only solution may be a somewhat extreme one, in the form of a prune job. Keep in mind that pruning needs to be done near the end of the vegetative state. If you prune cannabis plant after it has started flowering, you will end up cutting off parts of the plant where buds will grow, and that is a big waste.

You need to prune your weed plant, by as much as 30% to 50% before you start the flowering stage. Don’t fret about time and energy wasted growing the plant so big, because there is just no point in starting the flowering stage without pruning, if it has gotten too large during the vegetative growth stage.

Weed plants are pretty resilient too, so a pruning job usually will not kill them, but it will need to be done.

8. Top Up On Reflective Materials In The Grow Room

A good way to prevent a weed plant from growing too tall in the first place, and to stop it from stretching too much, and even to mitigate some stretching that has already occurred, is to use a lot of reflective materials. Whatever you do, never start growing in a room that does not have reflective materials on the walls.

This will help reflect light from the sides, and direct light at your weed plants from the sides. Since weed plants grow towards light, it will cause them to grow outwards in width, as opposed to just growing upwards in height.

Another solution here can be to put a small string of lights along the walls, instead of just having the lights at the top. However, beware that this can then result in bushy plants, so you better have a wide and deep grow room for this.

9. Use A Net To Curb Growth

The other solution, or at least partial solution to this problem, is to use a grow net to curb upward growth. This is a net, kind of like a fishing net, which you can span horizontally across your grow room.

The weed plant will grow into, around, and through the grow net. This will cause the plant to grow more in width and to have a wider canopy, instead of growing too tall.

The added benefit here is that you create a wider canopy which allows more light to get to the plant.

Conclusion

There we are folks, all of the causes, problems, and solutions to this issue of your cannabis plants growing too tall and skinny. You might think that a very tall weed plant is ideal, but really it just causes a lot of problems, so try to avoid it at all costs, and if it is already too late, you need to figure out a way to continue growing the plant without having it get much taller.

wondering why your weed plant is growing tall and skinny? here are the 5 main reasons and 9 simple methods to stop them getting too tall. ]]>