Why did my autoflowering plant stay so small?

by Nebula Haze

I recently received this email about a stunted, tiny autoflowering cannabis plant. Why does this happen? Stunted autos are a common problem, especially for auto-flowering strains with a very short vegetative stage. Keep reading to learn what causes autos to stay too small, and how to prevent it!

“This picture was taken last Fall. This my Purple Kush CBD Auto plant, quite pretty…

…until you see the actual size of it!

This came from an auto-flowering feminized cannabis seed that I dutifully planted outside in the Spring. Maturity was supposed to be 63 days but when I saw how little it had grown, I left it in as an experiment to see how tall it would end up. It didn’t grow even another cm taller. I ended up harvesting it at 113 days.

Any idea of what’s happened? Why did this autoflowering plant stay so small and stunted?

~Carmen

Why did this autoflowering plant stay so small and stunted?

Auto-flowering cannabis plants are on a tight schedule. Once they germinate, it’s essentially a “race” to the end of their life. That’s because their ancestors (“Ruderalis” wild cannabis plants) originated in Siberia where summers are just 2-3 months long. As a result, most auto-flowering strains start making buds at around 1 month from germination, and are ready to harvest when they’re just 2-3 months old.

What does this have to do with an auto-flowering plant staying small?

An autoflowering plant stops getting taller when it’s about 6 weeks old for most strains, and even earlier for faster-flowering auto cannabis strains like Purple Kush CBD Auto (which can be ready just 9 weeks from germination). That means that if your auto-flowering plant has a slow start for whatever reason (overwatered, cold, not enough light, other stress, etc.), it might not get very big before it stops growing taller.

Short vegetative stage – Most autoflowering strains automatically start making buds (they start “flowering”) around 4-5 weeks old.
Plants stop growing in the flowering stage – Auto-flowering plants typically stop getting bigger not long after they start flowering.
Small plants that start flowering stay small – If an auto-flowering plant is still small when it starts flowering, it won’t get any bigger.

This Purple Kush CBD Auto must have had a slow start, and started flowering before it had a chance to get very big. As a result, the final size was really small.

Here’s another example from our reader Hypermx, who experienced the same thing with his autoflowering plant.

I’ve had it happen as well. This auto-flowering plant went through stress at the beginning of its life (a person fell on it… okay it was me), and as a result never got big before it started flowering.

Just to give you an idea of how much an effect stunting can have, these are both the same autoflowering strain. You can see how much smaller the plant was that got stressed at a young age compared to the auto-flowering plant that was given good conditions from the beginning.

You want to avoid stunting to get the best yields from auto-flowering strains. Small plants can’t make big buds.

Unlike autoflowering strains, photoperiod plants have the luxury of being able to stay in the vegetative stage for as long as you want. That means you can recover from stress or problems and still get plants big enough to produce good yields. But with auto-flowering strains, you need to think about your grow as if you’re in a race to the finish line, and start strong.

I hope that helps reveal the mystery of why an auto-flowering plant can stay so small. Whenever growing autos (or any cannabis plants, really), I highly recommend germinated an extra seed or two, just in case something happens when they’re young or some plants grow better than others.

Bonus: Recommended Autos to Prevent Stunting

These auto-flowering cannabis strains were chosen because they are extra stress-resistant and easy to grow, yet produce good yields and outstanding bud quality.

GG 4 Autoflower – This version of Gorilla Glue #4 is easy to grow and tends to grow fast. It is a forgiving strain that can handle a bit of stress and is ready to harvest at 70 days from germination.
Cinderella Jack Auto – When I grew this strain, it produced the densest and most potent buds of that entire auto-flowering grow. It responded well to plant training, and produced good yields even though it was in a crowded tent with 7 other autoflowering plants. Harvest at 80 days from germination.
Planet of the Grapes Auto – Delicious grapes smell, high potency, medium height, and super easy to grow. This strain is something special! Harvest at 80 days from germination.

The GG 4 Autoflower I grew in the very front (right behind the green bar) thrived in a tiny grow tent (copy this setup).

The Cinderella Jack Auto I grew produced ultra-dense buds.

Planet of the Grapes Auto produced outstanding bud quality.

About the Author: Nebula Haze

I started growing weed in 2008. To be honest, in the beginning, I struggled. There just wasn’t great information available for cannabis cultivation. I had to find my own way through trial and error. After I had figured out how easy it could be, I decided to create GrowWeedEasy.com in 2010 with my partner Sirius to make cannabis-growing information easily available to everyone who wants to grow at home.

Weed companies charge way too much for subpar weed, and we want home growers to learn how easy it is to grow higher-quality buds than most weed you can buy. The secret doesn’t take a ton of money or require you to learn special tricks. You just need good genetics and the right information so you get the best results for the least amount of effort.

That’s why we’ve made all the tutorials on the website easy and straightforward to follow. If you follow our instructions like a recipe, your cupboards will soon be overflowing with weed. I hope you enjoyed this article about how to prevent stunted autoflowering plants. Don’t hesitate to contact us to share your experience or let us know your favorite auto-flowering strains. Also, we’d love to see your plant pictures so we can feature them in our weekly newsletter!