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A Guide to Growing Autoflowering Cannabis Seeds

April 10, 2017
When you decide to start growing cannabis, you might find yourself looking at online seed catalogs. Here you’ll see companies offering strains that are dubbed “autoflowering,” but what does this mean and why might a grower choose autoflowering varieties of cannabis?

What Is Autoflowering Cannabis?

The concept of autoflowering strains is simple: in time, they will automatically flower as opposed to waiting for a specifically timed light cycle. In other words, the plants begin to flower all on their own after a relatively short vegetative period of 2-4 weeks.

This unique process is created when breeders fold in genetics from Cannabis ruderalis, a subspecies of the cannabis plant that is known for its autoflowering attributes and short stature.


What Is Cannabis Ruderalis?

Crossing the autoflowering ruderalis with indica and sativa varieties results in a plant that doesn’t rely on photoperiods to flower, but rather grows and flowers on its own time.

The Pros and Cons of Growing Autoflowering Cannabis Seeds

There are a number of reasons to consider autoflowering varieties for both indoor and outdoor cannabis:

  • When grown outdoors, autoflowering plants will start producing buds no matter how many hours of sunlight you are receiving; this means you don’t have to worry about running a light deprivation system or supplementing light if you are trying to achieve multiple harvests in the season.
  • When growing indoors, autoflowering strains allow you to rapidly grow strains from start to finish as they generally complete maturation after three months.
  • Autoflowering plants can receive more than 12 hours of sunlight a day and create bigger buds in less time than many regular cannabis plants.
  • Autoflowering plants are small and stealthy; they are perfect for closet grows or growing outdoors where you don’t want your neighbors to see what you’re up to.

Growing Cannabis Indoors vs. Outdoors: 3 Key Differences

There are, however, reasons why autoflowering plants are not as popular as regular cannabis indica and sativa plants. Autoflowering strains are small in stature and do not produce large yields. Other issues with autoflowering strains include higher electricity bills and an inability to really train your plants to make the most of your grow space.

Since the introduction of original autoflowering strains in decades past, significant improvements have been made to these genetics. First, potency in autoflowering varieties has increased significantly since their initial introduction. Also, there are now hundreds of types of autoflowering seeds being sold, giving you a large selection to choose from. Because of these improvements, autoflowering seeds are worth a shot for any curious gardener looking to try something new.

How to Grow Autoflowering Cannabis Strains 

Autoflowering strains require some preparation, as they will grow quickly and start to flower whether or not you’re ready for them. However, follow these steps and you should find success in your autoflowering garden.

1. Training Your Plants

Generally speaking, you’ll want to train your plants while they are in vegetative growth. For autoflowering plants, this period could be as short as two weeks which means time is limited.


How to Train Your Cannabis Plants for Better Yields and Potency

To start, consider topping your plant after it has developed three nodes to promote a more even canopy. Another LST (low-stress training) method involves training your plant by pulling it down sideways to create new upward growth. Once your plants do begin to flower, you should not top them. Prune your plants conservatively for no more than one week into flowering.

2. Climate Considerations

When you are growing autoflowering plants, you’re allowing plants to flower when they should be in a vegetative growth. Because you don’t need to follow photoperiod light cycles, many people start autoflowering plants early in the season (e.g. March) or late in the season (e.g. September). For this time of year, it’s important to remember that the plants still need warmth to grow, and there also might be considerable rain putting the buds at risk of rot. To combat these issues, consider growing in a greenhouse to provide protection from the elements.


How Autoflowering Cannabis Strains Became So Popular in Central Europe

3. Go Easy on Feeding

Autoflowering strains do not need to be heavily fed due to their small size and the short amount of time they spend in the vegetative cycle. Feed very lightly and understand that they don’t need as many vegetative growth nutrients such as nitrogen. Also note that these vegetative nutrients are best put to use if they are readily available for the plant to utilize quickly.


What are the best nutrients for growing cannabis?

4. Harvest Gradually 

Autoflowering plants often do not have time to develop a canopy, which means you will be keeping buds that are lower down on the plant. Because of this, it’s a great idea to harvest your plants sequentially. First take the colas, then allow more time for the lower buds to dense up before they are harvested next.


When is the right time to harvest cannabis plants?

5. Prepare Your Next Crop

To get the most out of autoflowering seeds, it’s a good idea to prepare your next batch of plants as you are harvesting. This means popping seeds before you harvest your current plants so that your room is continually producing. Because the plants autoflower, you can have plants that are just starting out in the same room as those that are finishing without worrying about the lighting.


Cannabis Seeds 101: All You Need to Know and More

How to Find Autoflowering Cannabis Seeds

Autoflowering cannabis seeds are most easily found through seed banks and seed banks online (note: just be sure to read and understand the legal fine print about purchasing seeds online). Seeds may also be purchased at some local dispensaries, though depending on where you are, they can be difficult to track down at retail outlets.

Have you tried growing autoflowering strains before? Share your experience in the comments below and let us know how they turned out!

Trevor Hennings's Bio Image

Trevor Hennings

Trevor is a freelance writer and photographer. He has spent years in California working in the cannabis industry.

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  • fullduplex

    It’s nice to finally see the auto coming out into the light of the cannabis main stream. Years ago when first working with autoflower genetics, the plants were small, and the yields were about the same. Fast forward about 10 years now and the game has changed. They are no longer the small plants that we were used to. Major brands have really stepped up the game, and the private breeders have really done some amazing things.

    I’m also glad to see someone like Leafly taking the time to post an article that is not smashing Cannabis Ruderalis. We’d love to talk more to you guys about the evolution of the auto over on

    • Mike Clay


  • Jhony Blaze

    Auto flowers are a great choice , i’ve had great experience with some of them…. Mephisto is a great example Of awesome genetics

  • Two Bears

    Its about time Autos got some love.

    Autos are perfect for medical patients that want to grow their own medicine

    Small plants. Equal less space needed for. A grow.

    Autos need only about 1/4 the nutes.

    Both veg abd flowering plants can bd grown in same space. No need for separate tent.

    Use smaller pots 3 gallons (11 liters) is all you need for an auto.

    Need less soil or coco.

    Put more plants in less space.

    The newer autos can pridyce 100-150 grams of buds per meter.

    Its long overdue for autos to get respect

  • Pelu Maad

    Has anyone had any success with autoflowers and an Aerogarden? I’m going to try Green-o-matic in a 9 plant Bounty with a little extra CFL lighting…..

  • Fishanfly

    Well…have been growing for many years…am licensed in Canada….last crop planted (some seed/some clones) but ….how could one of my plants turn into an auto flowering plant???? I am bewildered…and I know what I am doing…but how can this happen????.


    I tried several high CBD auto strains from seeds I got from Canada. They were much smaller than what I was used to growing from the clones I get here in the SF Bay area. I started them indoor early in the season and then when the sun warmed up and nights were not to cold, I put them in my outdoor hydroponic setup. This article explains a lot of what I experienced. I noticed that they didn’t like the typical PPM concentrations I would run for other plants. The leafs were getting burned, so I cut my nutrients down to about 75% of normal. I was surprised they didn’t stretch more when they started budding so early. I did notice that the tops were ready to harvest, but lower down there were still smaller buds, not yet developed. I harvested all at once and just scraped off the bud-lets to go in my trim bag. The strains were all 20-30:1 CBD:THC and I got enough to makes some meds. Dried weight was about 250g/plant, less than half of a normal plant.

    The great thing about auto seeds is that a beginner doesn’t have to worry about the timing for their lighting. And they are much smaller, easier to manage, for people growing stealth in their closet!

    • Benjamin Bartel

      Do you remember where you bought your seeds from, this looks exactly like what we are looking for. TIA

  • Ronaldus_Maximus

    Started growing last June. Started with white widow autos and haven’t looked back. Smallest yield from one plant was 3 oz dried and cured . Best yield was 8 oz dried and cured.
    If you grow autos, don’t use chemical ferts. Use real soil. Much more forgiving and generally a better product.
    My first grow I used chem ferts and it was ugly. Switched to organic soil and it’s almost too easy now.

    • tonyc

      I have a question. Was this an indoor grow ? I have some WW auto seeds coming for my new indoor tent. How many hours of light do you give them ? Thx

      • William E. Boyd

        I suggest twenty hours of light and organic nutrients work best

    • Teery

      What was your area size and light wattage uses?

    • Lindz

      Hey. I just posted about a problem I’m having w my plants. They turned out to be autoflower, but after producing pistils they stopped and just keep getting bigger. Can u please see what I wrote and let me know what u think? If u have time. Thank u!

      • James Miller

        go to 12 – 12 lighting

  • Russell Walker

    Hi I just 🌟 to grow auto seeds pretty new to growing I have a master kush which looks pretty good and super skunk looking good but my white widow is looking yellow and not growing as quickly as other 2 any help or advice would be great

    • Tony C

      If you’re growing in a tent in soil,….Check the soil ph level. You might need a 10-10-10 liquid fertilizer. And don’t soak the soil. Over watering is problematic too. Just keep it lightly moist and stay away from the stem when watering.
      Also the temperature has a factor, 70 – 75 degrees is perfect with 50 – 60% humidity.

  • Fishanfly

    I want to believe Monsanto did it but no proof…cloned the mystery auto flower … grew another but it is bunk cannabis …straight up for me only..

  • Lindz

    Hey. Question. I have 2 big girls that turned out to b autoflower plants. They started to produce pistils at the same time, so I reduced light cycles to 18 on 6 off. THEY STOPPED PRODUCING PISTILS, so I went back to 24 hr lights. This is now almost 3weeks later and not much more has happened. Can anyone help me on what I need to do? They r so big now that there outgrowing there tent. I bought the seeds from a reputable online store. One was supposed to be Durban Poison, but looks like a indica dominate for sure. And was NOT to be autoflower. Same w the other, was supposed to be Currant Kush. She looks like a indica dominate plant for sure. Both were feminized seeds and shouldn’t have produced pistils untill I changed light to 12/12. Well I never got to. Please help!!

    • I bought 2 different auto strains from a reputable online store myself. One started blooming like autos do, but the other wouldn’t bloom until I switched the light to 12/12. I harvested the real auto almost a month ago, and the other still has 2 to 3 weeks to go it looks like. I contacted the place I ordered the seeds and told them I got photo sensitive seed when I ordered autos was told I’m wrong, they ams could not have made a mistake! Well, they did.

  • Shane Lawson

    I live in southern cali and i’m trying to figure out if I’m better off starting my seeds inside,grow them till may and then plant them outside.Or I’ve heard that down hear if you plant outside now I’ll get a crop in June and then regrow and harvest again in oct.

  • Fiona Johna


    In the Scottish Highlands newbie to grow, I have 3 auto flowering seeds can I grow these in doors in a well lit (by daylight) room. I have no other lights and I guess it is too cold, even in summer to put outside?

    • Plantlife

      You should be Ok. Doubt it would be too cold in the warmest 3 months of summer, if not 4 or 5 – Ruderalis are supposed to have originated from Russia/Eastern Europe, and cold-tolerance is why they have been used as genetic material. If you are worried, bring them in at night. Start them inside (if you haven’t already) in a 1 litre pot, and transplant into approx 11 litre pot after about 20-25 days: check the bottom of the 1 litre pot to make sure roots aren’t showing: if they are, move to final pot. The main thing for you is maximising sunlight, i.e. moving your plants into the sun throughout the day if necessary; and maybe sheltering them from particularly strong, cold winds, or harsh nighttime temperatures.
      To answer your question more specifially, they would be ok to grow inside if you get enough sunlight.

  • Brad Jensen

    I am currently growing White Widow autoflowers from ILGM that are over seven feet tall! The yield on these is going to be giant also. My previous batch of ILGM autos were only three feet tall but still had high yield. Heavyweight Fast and Vast auto also turned out a high yield with five to six foot plants. Fruit Punch auto is also good.

    If you shop around, you can find high yield autos. I also grow photperiod plants. I am a small commercial grower in the USA.