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How To Set Up Your Grow for Autoflowers

By Colin Gordon & Ben Owens

Knowing how to set up your space will make a noticeable difference in the performance of your plants. You want to make use of your space and make sure your plants are at their healthiest. 

Due to the shortened timeline of autoflowers, it is vital that the first 5-6 weeks of its life are set up for success. A plant that is happy and healthy from seed to harvest will produce the best harvests.


As you may recall from our first piece on autos our process for germinating autoflower seeds is to put them in paper towels at temperatures between 72-85ºF for 3-4 days. They should then be put directly into the intended final pot. Be extra careful to avoid breaking the tap root when planting.


One of the variables in determining when the plant goes into flowering is the diameter of the pot. When your plant’s roots begin circling begin circling the perimeter of the container, that’s a trigger signaling to the plant to focus on flowering, which is why it is important to start your auto in its final pot.

If absolutely necessary, you can germinate into a small container for up to the first three weeks of its life and then transplant it (to the final pot or bed), but this is still a second choice to putting it in the final container as it has to be done precisely to avoid triggering flowering hormones.


Pot size will be a significant determinant in the size of the plant when it comes to autos. Autos can grow to be 2-3x the diameter of their pots. 

There is a diminishing return going beyond 7-10 gallons where yields seem to cap. But I have seen significant increases in average plant size all the way up to at least 7 gallons. I will say that a smaller diameter pot will likely produce a faster-flowering plant in most scenarios. The swing in flowering time is typically between 1-3 weeks total of the plant's life. 

The first few weeks of an auto’s life, it doesn’t do much, but weeks 4-7 as it transitions to flower is when the plant is actually growing. If the roots signal early, you’re losing valuable growth time. Sacrificing 7 days of growth while a plant is at its peak will have a dramatic impact; 7 more days during this rapid growth phase would create a much larger plant.


Substrate is very conditional. It is all a matter of your end game and what you want to dial in. 

The #1 thing with autos and substrate is choosing something with higher porosity so that it can root out quickly in the beginning. An exception would be outdoor and beds; a standard outdoor soil is fine. It is much warmer and those things are going to root out vigorously under the sun. 


To account for the doubling in diameter of my autos, I like to use a checkerboard grid.

I’ll put the 7-gallon pots with even spacing between them (ideally a diameter’s equivalent), and alternate placement with each row. Around week 6, I space them out a bit more.

In a 4x4’ space, you can comfortably get 4-9 autos per grid.


Remember, autos love light. uMole is determinant and factor, especially once the plant begins growing aggressively (Week 5+).

With higher uMole, you are typically going to get faster flowering and larger flower sets. 


Weeks 1-3: 150-400 uMole

Weeks 4-5: 500-800

Weeks 6-10: 800-1200

Finishing: 800

As you can see, your goal is to reach 800 uMole by weeks 4-5 and maintain or exceed that level for the remainder of the plant’s life. How much further you increase will depend upon the variety and the health of the plants. All varieties typically want at least 800 uMole. After that, titrate up and see how the plants react.


When flowering from seed in general, ventilation and circulation is important. I try to keep "daytime" temps around 80-86ºF (ambient room temps) and humidity above 40%. 

These plants transpire a lot and can put a lot of humidity in a small space, especially when going through their rapid growth phase. Higher humidity (60%) is preferred, but anything over 40% should be ok.


You will want to feed around half of the EC of a typical plant. There are a few of the more sativa-leaning varieties that feed heavier, but a typical auto feeding schedule starts at half of what your photo period plants consume and ramps up as needed. Keep it simple. 


I personally don’t top autos. Some of the Sativas you could top and have good results, but I don’t think that in most experiences topping is going to improve the overall yield and quality. There are exceptions.

Let your auto grow to its natural morphology, and defoliate a little bit depending on flowering, but they should do most of the work for you.

It is important to keep your autos vertical. Keep the plant perpendicular to the substrate and try to avoid having the plant leaning or tilting as it can stunt and change growth.


It is a complex web of variables that factor in to how an auto grows and at what rate it will finish flowering. Some are more susceptible to environmental impact than others (aspects like light intensity, diameter of the pot, etc.). 

Some varieties’ flowering times are give or take 5 days, others are a 20-day window. And there are varieties within each variety. 

Currently in the program, our Zweet Autos are the most consistent in multiple environments. They have the least variation; you get a big plant no matter what, even in smaller pots. 


As cannabis, nothing is different, between an auto and a photo period plant aside from the flowering trigger in the plant. Fundamentally, it is as if you were putting a photo period plant in 12/12 right off the bat as far as plant morphology and needs. 

An autoflower isn't dependent on light cycles for its process. Other than that, it is just cannabis. 

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