Why are my cannabis seedlings so tall?

Question: Why are my young marijuana seedlings getting tall and dying? They're growing all stretchy with long stems, and aren't making new sets of leaves.

Small marijuana seedling with magnesium deficiency - tallTall marijuana seedling in bubbleponics setup - magnesium deficiency - too wet?

These cannabis seedlings are growing tall and thin (and falling down) because they need more light.

These cannabis seedlings are tall, thin and falling down because they aren't getting enough light


Answer: When marijuana seedlings are growing tall and thin like that, it means they need more light.

Too Tall Seedlings Are Caused By Lack of Light

"Leggy" seedlings need more light

Too-tall seedlings need more light!

Cannabis seedling needs more light! It's getting tall because it's stretching for light!When young marijuana seedlings are starving for light, they often show signs of lots of other problems, but if they're getting really tall without making any leaves, it's a sure sign it needs a brighter environment.

To increase the amount of light, you either need to get stronger grow lights (what grow lights work for growing cannabis?), or move your current grow light closer to your plants.

Some growers bury the extra stem to make seedlings short again, which works, but as long as you start giving your seedling light it will do a "push up" and rise back up, strengthening its stem in the process! Here's what to do right away…

Get 1-2 CFL bulbs and keep 2-3 inches away from the tops of your seedlings (be careful not to let seedlings grow into the light!)

Get 2 x 40W 'daylight' CFLs (can support 1-4 seedlings)

Buy a 40W "Daylight" CFL to startBuy a 40W "Daylight" CFL to start

1 x Light Sockets and 1 x Splitter

Get light sockets to power your CFL grow lightsGet a light splitter

You can get more light later when the plant is making buds, but getting 2 CFLs should stop the stretching so you have a few more weeks.

Example of keeping CFL grow lights very close to your young cannabis plants

Keep CFL grow lights as close to your marijuana buds as possible in the flowering stage, but don't accidentally burn them!

After adding light, you'll see the new growth is much bushier and closer together, but the original stems will not get new leaves. Some growers will bury plants like these up to the point where there's leaves, but there's nothing wrong with just growing plants out as long as you have the height! 

Example of cannabis plants that need more light

Learn about other common cannabis seedling problems!

What Do Healthy Seedlings Look Like?

Common Seedling Problems

   1.) Overwatering

   2.) Underwatering

   3.) Nutrient Problems

   4.) Too Much Heat

   5.) Wrong Amount of Light

Frequently Asked Questions About Seedlings


Help! My Leaves are Dying!



Jump to…

Plant Problems & Symptoms



Return to Top of Page