Why Are My Weed Seedlings So Leggy

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When you germinate your cannabis seeds, it really is the start of an amazing journey. You’re probably all excited about seeing your weed plants grow big and tall, flower, and provide you with some killer bud that will knock your socks off when you smoke it.

If it’s your first time growing weed from scratch, you might be a little nervous, and yes, you have a right to be nervous, as there is a lot that goes into growing some righteous ganja.

Now, the problems can start very early, in the seedling stage even, and one of these problems is when your seedlings are leggy, or in other words, tall and floppy. Today we want to address a common growing question that comes up: “Why are my seedlings so leggy?”.

Short answer: seedlings can get really leggy, which means that they are way too tall, with really thin stems, and it’s usually due to issues with light. Generally speaking, if your seedlings are not getting enough light, they will get leggy.

Let’s take a closer look at this common issue and most importantly how to fix it.

Why Are My Seedlings Leggy?

When it comes down to it, leggy seedlings are caused by a lack of light. Now, this in itself could result from a number of issues.

Maybe the window you are growing your seedlings in does not get enough light. Maybe the lights you are using are too weak, or the lights may also just be too far away from your new cannabis seedlings. Whatever the case may be, when there is a lack of light, seedlings will grow really tall and skinny.

The reason for this is due to the natural biology of plants. All plants, which includes cannabis, need to get a certain amount of light.

  • Yes, plants are naturally trained to grow towards the light, as it is after all one of the main sources of life for them. If you pay attention to your plants, you will notice that they always grow towards the light.
  • Now, if your cannabis plants are too far away from the light, or the source of light is too weak, they will grow towards that light source at an accelerated rate in order to try and survive.
  • Simply put, they want to get closer to the light source so they can absorb more of those UV rays. Yeah, it is natural for your cannabis plants to grow towards the light, but when they do so at an accelerated or excessive pace, causing them to get leggy, or really tall and skinny, it can cause some serious issues.

Let’s move on and take a closer look at the various problems which you may run into if your seedlings are leggy.

5 Issues Caused By Leggy Seedlings

Yes, there are indeed a few different problems that you may run into if your seedlings are growing all tall and floppy. What are the problems caused by leggy seedlings?

1. A Sacrifice In Stem Width

For one, there is only so much accelerated growth a cannabis plant can manage. However much it has to make up for in height growth to get closer to the light, it will sacrifice in terms of stem width.

This means that your cannabis plant will have a really weak and floppy stem, which then leads to other issues.

2. Your Cannabis Plant Cannot Stand Upright

A Floppy cannabis stem then leads to the issue that the plant simply cannot stand upright on its own. The faster in grows in height, especially in comparison to how fast it grows in width, the weaker that stem will get.

Eventually, or pretty quickly actually, your cannabis seedlings will not be able to stand upright on their own. They will get all crooked, floppy, and unstable because the thin stem cannot support the tall seedling.

3. Serious Issues Once Vegetation Starts

This issue of a weak stem not being able to support the tall cannabis plant only gets worse as the seedlings begins vegetating.

Once the cannabis plant starts growing taller during the vegetative state, especially when it starts growing a lot of fan leaves, it will become far too heavy for the stem to support, often causing pot plants to fall and rest on their side.

4. Problems When Transplanting To An Outdoor Location

The next problem you get here, in relation to those tall and weak stems, is that if you happen to plant your seedlings outside, after they have grown for a while, is that they will not be able to stand up to nature very well.

A strong cannabis seedling with a thick stem won’t be bothered too much by rain or wind.

However, a cannabis plant with a really weak stem is susceptible to bending, breaking, and outright snapping when it gets windy or if the plant is rained on.

5. Increased Susceptibility To Pests & Disease

The final problem that comes along with having really leggy seedlings is that they become much more susceptible to mold, mildew, other types of fungus, and pests too.

Simply put, they are close to the ground where all of those pests and diseases like to hangout.

The more of your seedling is near the ground, the more susceptible it is to all of these things.

How To Prevent & Solve The Leggy Seedling Issue

Cannabis seed sprouting

There are a few steps you can take in order to prevent this issue of tall and floppy seedlings, as well as a couple steps that can be taken to correct seedlings that have already become leggy, so let’s take a look at these right now.

A South Facing Window

If you really want to grow your seedlings in a window, be sure that it is a south facing window, so they get the most and strongest light every single day.

If you do not have a good south facing window that gets a lot of sun, you may just want to use some light bulbs, a soft white fluorescent bulb just a few inches away from the plants.

Lights Need To Be Close

The best way to grow seedlings is with a soft white fluorescent light, but if the lights are too far away from the seedlings, you will cause them to get leggy.

So, the lights you are using should never be more than a couple of inches above the seedlings. If they are any further from the seedlings than a couple of inches, the seedlings will stretch and get leggy to try and get closer to the lights.

On that same note, increasing the strength of the lightbulbs, or in other words, getting a stronger lightbulb may work as well, but you do need to be careful because seedlings are sensitive to light burn.

Make It Windy

One cool trick you can use to ensure that your seedlings grow thick stems, or so that leggy seedlings quickly bulk up in terms of stem width, is to make it a little windy.

Brush your hands over the plants a few times per day, or better yet, use an oscillating fan to blow on the plants for a few hours per day.

This actually tricks the cannabis plant into thinking that it is growing in a permanently windy environment. This is turn causes the cannabis plant to release chemicals into its stem which are intended to thicken and strengthen it.

Bury Them Deeper

Now, if your seedlings are already very leggy and you are concerned about the strength of the stems, something you can do is to bury them deeper in the soil or planting medium.

Simply put, if you bury an extra few inches of the stem in the soil, right up to the bottom leaves, then the stem will be supported by the soil, and you can then move the lights closer to the seedling, to prevent further height growth, at least growth that is too fast.

Combine this with a couple of hours of wind per day, and your problem should be solved.

Other Causes & Solutions To Leggy Seedlings

Yes, there are a few other things which may cause your seedlings to get leggy, but these are much rarer than the light issue, but still worth mentioning nonetheless.

It’s Too Hot

If it is too hot, seedlings may also get leggy in order to try and get more air higher up above. Of course, this does not really work in an artificial growing environment, such as in a grow room.

Seedlings will stretch up to get more air up above, but in a grow room, it just gets warmer the higher up the plants go. Therefore, the solution here is to cool the air down a bit.

The best temperature for seedlings during the day is between 65 and 70 degrees Fahrenheit during the day and 55 to 60 degrees Fahrenheit during the night.

Inconsistent Watering

Another cause of leggy seedlings can be a lack of consistent watering. If you are noticing that the tray or dirt completely dries out between watering, you are not providing your seedlings with enough consistent water.

You need to make sure that your seedlings are always fully hydrated, and this is best done by watering them from the bottom up.

Place your tray with seedlings into some water for a few minutes so they can suck up water from the bottom up, thus ensuring that they are fully hydrated.

Seedlings Are Too Close Together

The other reason why your seedlings may become tall and floppy is because you have planted them way too close together. Each seedling requires around 5 inches of space between it and the next one.

If they are too close together, they will begin to compete with each other for light. They will begin growing at an accelerated pace in order to beat the other plants, so they can get the most light.

Therefore, the easy solution to this issue is to ensure that you have planted them far enough apart so they do not throw shade on each other, and are therefore not forced to compete for light.


Generally speaking, leggy seedlings are usually always caused by a lack of light, but it may also have to do with temperature, watering, and how close you planted seedlings to one another.

So, you need to figure out what the problem is and take immediate corrective action, or else you will end up with super weak and tall weed plants that cannot support their own weight, which often leads to poor growth, or even death.


My passion for the sticky icky started nearly a decade ago, and it all began when I first laid my eyes on the beauty that is the marijuana plant.

I cover all aspects of growing from equipment recommendations to plant health/care tips to help both new and experienced growers.