Cannabis Seedling Growing Too Tall: Tips To Fix And Prevent It

Are your cannabis seedlings growing too tall and fragile? This common issue can lead to weak plants and poor yields if it is not addressed early. Let’s dive into why this happens and how you can keep your seedlings strong and compact from the start. Here’s your guide to fixing stretchy seedlings. 

About Cannabis Seedling Phase

Think of cannabis seedlings like tiny genetic capsules, designed with one mission: to grow into a plant. They’re pre-programmed for survival, carrying everything a future plant needs to simply get started. When you expose these seeds to moisture and darkness, they are triggered to germinate, which sets off a process that can’t be reversed. 

During the first few days of its life, a seedling doesn’t require any external nutrients. It comes equipped with all the essential nutrients it needs to begin its journey as a plant. This little energy reserve helps it establish itself in its growing environment. 

Under the right conditions, the seed’s shell or husk cracks open, allowing a taproot to emerge and dig down in search of water. Shortly after, you’ll see a sprout break through the soil, and it will grow its first baby leaves, which are called cotyledons. 

As the seedling grows, you’ll notice the development of its first true leaves. While the taproot grows in search of water, the new leaves start capturing light for photosynthesis. It will grow for a few weeks until the seedling is big enough to grow more leaves and start growing further. This is the seedling stage. 

Seedlings Need Perfect Lighting Conditions 

As you can understand, seedlings are super important for a healthy cannabis plant. And for them, light is important. To ensure your seedlings grow healthy and strong, it’s crucial to provide them with the right time and amount of light as soon as they sprout. 

Generally, cannabis seedlings thrive under about 16 hours of light per day, with an intensity of 375 lumens and 4000 lux. 

To achieve this, you can use a single 12W CFL bulb for every 1-2 seedlings. Here, position your bulb around 2 to 3 inches above the seedling and closely monitor their growth, making sure the plants don’t come into contact with the bulb. 

But that’s not it. An improper light setup can cause a lot of problems for your seedling. It’s also important to consider the type of light you’re using. Lights with a high red light percentage can cause seedlings to stretch. Let’s look into it in the following section. 

Causes of Abnormal Seedling Stretching 

Abnormal stretching during the seedling phase of your cannabis is a sign of stress, especially with light deprivation being the most common cause. As mentioned above, just as taproots dig for water and nutrients, the upper part of the plant will stretch if it isn’t receiving enough light. 

This is a survival instinct where the plant uses its stored energy to grow taller in search of light, mimicking how it would try to outcompete other plants in nature. While there’s no competition indoors, the seedling still behaves as if there is. 

For example, placing the pot in the shade under a windowsill can trigger this stretching behavior. This issue can be even more pronounced under artificial lighting. If you’re new to growing cannabis, you may find it confusing. You’re already providing enough lighting! However, the distance and intensity of the light source have a lot to do with this. 

For instance, a 200W MH bulb placed far from the plant may be less effective than a 20W CFL bulb a few inches from the seedling. This happens even when you consider that a CFL bulb is nowhere as strong as an MH bulb. 

Additionally, your seedling has a limited surface area to absorb light due to its small leaves. While a 200-watt bulb radiates over a large area, the seedling only uses a small portion of it. Conversely, a CFL bulb a few inches away can deliver most of its 20W efficiency. 

Other Potential Causes 

Besides light deprivation, various other factors could cause your cannabis seedlings to stretch. One common cause is inadequate nutrient content in the soil. 

Cannabis seedlings thrive on nitrate-derived nitrogen. Unlike ammoniacal nitrogen, nitrate-nitrogen is easier for your plant to absorb, promoting shorter and bushier growth. So, if your seedling stretches despite ideal lighting conditions, consider checking the ammoniacal nitrogen levels in your soil and fertilizer. 

Another cause of leggy seedlings is excessive heat. While seedlings prefer warm and humid conditions, too much of it can cause the leaves to grow slower than the stem. This leads to a tall and stretchy seedling. 

To encourage the healthy development of your seedling, try to maintain temperatures of 66-68°F (19-20°C) during the day and around 55°F (13°C) during the night. 

Lastly, stretching can occur if seedlings get too much or too little light per day. While some growers keep their seedlings under 24 hours of light, it’s still better to stick to 16 hours. 

Remember, your seedlings are delicate, and too much light can easily stress them out, leading to stretching. Those dark hours are vital for your plants to grow healthy roots and respire. 

Fixing Leggy Cannabis Seedlings 

Now that you know what causes seedling stretching in cannabis, let’s learn how to fix the problem. Remember, you must address this promptly to get the most out of your cannabis seeds. While it may seem like the damage is done, use the following tips to save your seedling: There’s still time. 

• Bury the Seedling Deeper

If your cannabis seedling’s stem has grown too tall, one effective way to prevent further stretching is to plant it deeper in the soil. So, carefully dig up the seedling and replant it, ensuring the stem is buried deeper. 

This method is straightforward and provides long-lasting benefits by improving the plant's health and stability.

How does this help? 

Well, when cannabis seedlings grow too tall, their stems tend to be thin and fragile, making it hard for them to bear the weight of leaves and future buds. Eventually, the seedlings can topple and die. Deep planting prevents this problem by offering support for the stem and promoting a better root system. 

Although the process is simple, you should be careful. If you want to transplant it from a small container to a larger one or directly into the ground, make sure you bury a part of the stretched stem beneath the soil surface.

To do this, prepare your other container first by filling it with soil. The soil should be loose and easy to drain. Next, gently remove the seedling from its container being cautious not to harm its roots. If it's in a jiffy pot or any pot made of compostable material, you can plant it directly without disturbing the roots.

Now, make sure that the elongated stem is buried but keep the top leaves exposed with only a small section of the stem above ground level. Typically, it works if you bury just 1-2 inches of the stem. Adjust as needed based on how tall your seedling is.  

Gently press the soil around the stem to create contact with the buried part and stabilize the seedling. This will also encourage roots to grow along the buried stem, thereby creating a massive root system. 

Once you've transplanted, give the seedling a good watering to help settle the soil around its roots and stem. Take care not to overwater as the seedling may still be sensitive to water.

However, if the seedling is so weak that you can't transplant it at all, you can simply add more soil to the base. The problem is that the soil gets dislodged when you water it, so add more soil and press it firmly so the seedling stays in place. 

After planting the seedlings, it's crucial to keep an eye on them. Make sure they get light, but avoid direct sunlight exposure in the beginning as they adjust to their new surroundings. Keep the soil moist. After a few days, you can provide a low-strength nutrient solution to help them recover. 

In essence, when you see weak seedlings remember that you have to act fast to prevent them from worsening further. If it's weak enough to topple, it means that it doesn't have a strong structure. By burying it in soil, you're helping the young plant withstand stress and create a better root system. Although you're probably worried about your plant at this stage, the good news is that it will promote a bushier growth pattern with plenty of leaves. In other words, the plant will grow more horizontally rather than vertically. 

• Use Stakes to Support It

You can also use stakes to support your seedlings. Similar to how they are used to straighten bending trees, they can help guide and support the growth of your seedling, too. Just know that stakes may not fix the stretching, which is often caused by light or environmental factors; they can stabilize the seedlings and help them grow stronger. 

Stakes also help the seedlings straighten themselves. Thus, by securing the seedlings to stakes, you can ensure they stand tall, preventing their stems from bending, snapping, or veering off course. This extra stability is particularly important if you notice that the seedlings are unable to stand upright. 

For stakes, you can choose any material. Hell, a straw would work, as long as you secure it correctly. But, a wooden piece will work better as it will hold the seedlings in place, unlike straws that can bend. Just make sure your small stakes are as tall as the seedlings to support them easily. You should be able to anchor them into the soil. While thinner stakes will work perfectly for seedlings, thicker stakes are better for bigger plants. 

To help a bent seedling, first insert your stake carefully into the soil, a few inches away from the base. Be careful not to disturb the roots. The stake must sit firmly in the soil or it will hurt the seedling when it topples. 

Next, attach the seedling to the stake using ties like plant ties or garden twine. The tie should be soft and shouldn't cut into the stem. Tie it barely enough to allow room for growth but not too tight.

Now, all you can do is watch your seedling and pray that it recovers. Usually, they recover, but in some cases, like damping off, they don't. Adjust the tie as the seedling grows, making sure it's not too tight for the plant. If everything goes well, the stem should become thicker and stronger reducing the need for staking. Once the plant is stable, you can carefully remove the stake. 

Again, remember that stakes can just support the plant. However, if the seedling is suffering from root issues, fungal issues, or nutrient imbalances, it won't be able to do much. 

• Fix the Lighting 

If you observe your seedlings growing tall and spindly with elongated spaces between their leaves, it's an indication that they lack adequate light. Other signs include pale or yellowing leaves and a general lack of vitality, but you must spot these signs and act immediately to prevent further stretching. 

As mentioned earlier, you need to place your light at the right distance and with the right intensity. So, depending on the lights you use, make sure they are placed at the right distance and produce enough light. As always, a 20-watt CFL bulb, placed 2-3 inches from the seedling, usually does the trick. 

Light is the most important factor for the plant to conduct photosynthesis. For seedlings, light not only fuels this energy production but also guides the plant on how to grow.

When light levels are uneven, young plants naturally lean towards the light to absorb more energy. This behavior, called etiolation, results in fragile stems that may break easily and struggle to support leaves. Adding light can address this problem and promote stronger healthier growth.

Apart from adding more light, you can also prevent them from stretching by enhancing the intensity of the light they receive. Stronger light levels supply the energy needed for seedlings to develop stems and lush foliage.

Another way to ensure your seedlings get light is to reduce the distance between your grow light and the plant. This totally depends on the type of light, though, so we can't tell you about the exact distance. For instance, fluorescent lights and LED grow lights are usually cooler and you can place them a bit closer than other powerful lights like MH or HPS lights. HID lights are so powerful that they can burn the plants pretty quickly, so be careful. 

If they do burn, they will die before you can do anything as they are seedlings. However, the manufacturer usually provides a lot of information about the appropriate distance and you can use that as a starting point. Also, reduce the distance gradually instead of doing it all at once as it can shock the plant. 

Another method to enhance intensity is by maximizing the exposure your seedlings receive through the use of reflective surfaces. Covering the walls of your growing area with materials like Mylar or matt white paint helps bounce light onto the plants ensuring they receive maximum exposure.

And, needless to say, pay attention to the spectrum of the light as it can significantly influence seedling growth. Cannabis plants have varying spectrum needs during their lifecycle with blue light (400 500 nm range) being particularly beneficial during the seedling and vegetative phases.

If you use a good-quality light with enough blue light, it will foster bushy growth in seedlings. Moreover, it will prevent stretching by reducing the space between the internodes. The stems grow thicker too. 

So, make sure your lights have blue light in them. But, rather than going for individual lights, it's best to get full-spectrum lights that are great for the entire lifecycle. 

Coming to the duration, seedlings will do well with about 18-24 hours of light per day, as mentioned earlier. You can also consider providing 24 hours of light for at least a week if they are stretching too much during the dark period. 

However, remember that while it's essential to provide light, you must strike a balance and avoid exposing your seedlings to excess light which could lead to stress and damage.

Also, keep an eye on the temperature around your plants as this is especially crucial during the seedling stage. Excessive heat can scorch the seedlings and dry out their leaves. So, ensure there's proper air circulation to reduce the heat. 

Preventing Leggy Cannabis Seedlings

Stretchy cannabis seedlings aren’t the end of the world, but they can still be a challenge to maintain and transplant. Plus, their delicate stems can be prone to fracture, and when they transition into the growth stage, their foliage may appear uneven due to the unusual growth they had as seedlings. 

So, it’s best to prevent this issue entirely. And you can do so by offering them an optimal environment for your seedlings from the start. 

You can consider growing your seedlings outdoors in direct sunlight. There’s no better alternative than natural sunlight. Once your plants have produced 2-3 mature leaves, you can then move them indoors, ensuring that the lights are placed at the correct height to prevent further stretching. 

If that’s not possible, you can follow the steps previously mentioned to provide your seedlings with the right amount of direct light at the right intensity. You should soon see your seedlings developing healthy growth with short internodes and compact, green foliage. 

Prevent Overcrowding

When numerous seedlings are packed tightly into a confined space, various problems can arise that make the plants stretch, including: 

Competition for Light: Imagine a situation where there are too many people but too few resources. What do you do? Naturally, you compete. 

Plants are no different. When you cram too many seeds in one container or any confined space, they will compete for whatever resources are available. Seedlings that aren't getting light when they are shaded by other plants will stretch themselves toward the light. They do this by elongating their stems in an effort to avoid being overshadowed by neighboring plants. While this stretching is a survival tactic, it often compromises the plants' strength.

Diminished Airflow: Adequate airflow is crucial for the development of seedlings. In conditions where airflow is frequently restricted, it often creates more humidity, which is bad for the plants. 

In addition, insufficient airflow can worsen heat stress, forcing the plants to elongate in a bid to find ventilated spots. 

Competition for Nutrients: Just like they compete for light, the seedlings will end up competing for nutrients as well. This competition can limit the availability of nutrients, causing seedlings to stretch as they struggle to absorb nourishment for healthy growth, especially if some plants are overpowering others to get more resources.

Heightened Stress: The overall stress from overcrowding can result in growth issues, including stretching. Stressed plants are more prone to stretching as they try to adjust to their challenging surroundings.

Many growers plant more than one seed in the container because some seeds may not germinate. And, when you have lots of seeds, you may plant a lot more with an intent to separate them later. However, if you observe your seedlings growing taller and thinner than usual with lots of spaces between leaves and weak stems, overcrowding might be a contributing factor.

To avoid overcrowding, here are a few things you can do:

Proper Spacing: Make sure each seedling has room to grow without being crowded by its neighbors. Aim for at least 2-3 inches between seedlings. As the plants develop, increase the spacing or transplant them to accommodate their increasing size.

Thinning Out Seedlings: Sometimes, it's not easy to transplant the plants even if you want to, especially when the roots get tangled with each other. This is because the plants grow pretty quickly. If you somehow try to transplant, you may end up losing even healthy plants, so your only option is to cull some of the weak seedlings to reduce competition and give the remaining seedlings a chance to thrive.

This not only helps maintain an even canopy in your grow room but also optimizes the use of available light and nutrients. It can also help you prevent pests and diseases that can occur due to overcrowded conditions.

Reduce the Temperatures 

Excessive heat in the grow room can prevent the seedlings from growing properly. While light and nutrients are usually the focus when addressing stretching seedlings, you should remember that temperature also plays a vital role in helping the plants grow well. If temperatures are too high, cannabis seedlings may respond by stretching their stems. Eventually, the stems become weak, and the seedling collapses. 

Cannabis plants are sensitive to temperature changes, but they are extremely vulnerable as seedlings. As mentioned before, they can tolerate and anticipate slightly cooler temps at night. This day-night temperature fluctuation can prevent stretching effectively. 

However, when temperatures exceed the appropriate range, various physiological changes occur in the plant that result in stretching. 

High temperatures can also speed up the plant's metabolism and promote quick growth. However, this rapid growth often sacrifices strength as the plant elongates to meet the increased metabolic demands without developing enough stem thickness and support. 

Moreover, fluctuations in temperature can disturb the equilibrium of growth hormones in cannabis plants, as known as gibberellins, which promote cell elongation. Excessive levels of gibberellins can lead to the plant stretching much more than required, which doesn't bode well.

If you notice that there's a lot of space between the internodes and the stems are more delicate than usual, the culprit could be excessive heat. To prevent this, you can use more fans that prevent hotspots in the grow room. Of course, you can use air conditioners too, but check the temperature frequently to identify heat stress and take necessary measures. 

Summary: Cannabis Seedling Growing Too Tall: Tips To Fix And Prevent It

Stretchy seedlings may seem like a setback, but with the right care, you can guide them back to healthy growth. By adjusting your light setup, managing nutrients, and creating optimal conditions, you’ll ensure your cannabis plants thrive from seedling to harvest. 

So, next time your cannabis seedlings start stretching, be quick. Fix the lighting conditions, support the seedling, and bury the stem deeper in the soil. After that, take the right measures to ensure the same problem doesn’t happen again. In any case, you can always rely on natural sunlight if tinkering with grow lights during this sensitive stage isn’t your jam.