Tips For Growing Autoflowering Cannabis Indoors And Outdoors

The introduction of autoflowering cannabis in the early 2000s revolutionised cannabis cultivation. Autoflowers grow fast, remain at a compact size, and don’t require special lighting schedules. In the past, these benefits were to the detriment of yield and bud quality. Today, however, modern autoflowers can produce a top-quality smoke with great yields—the new generation of autoflowering cannabis is in full swing. Find out everything you need to know about growing these specimens below.

Tips For Growing Autoflowering Cannabis Indoors And Outdoors

What Are Autoflowers?


Simply put, autoflowering cannabis initiates its flowering phase based on age, rather than a change in the light cycle. The “secret weapon” responsible for this trait is called ruderalis—a cannabis subspecies native to regions of Eastern Europe and Central Asia. Used to growing in harsh conditions where sunlight is scarce, this weed-like cannabis evolved to flower before the freezing weather sets in and there is no chance to reproduce.

The thing is, on its own, ruderalis weed is not very appealing. It produces meagre yields of tiny buds low in THC. But, things get interesting when ruderalis strains are crossed with robust, high-performing photoperiod species. With the right knowledge and expertise, breeders can create autoflowering versions of famous and beloved strains, without sacrificing much in the way of potency or yield. Suddenly, growing top-quality weed is a whole lot easier!

Is Autoflowering Cannabis Less Potent?

In the early aughts, when autoflowers first made an appearance on the cannabis community “mainstage”, these strains were pretty unanimously considered subpar weed. Aside from poor yields and unimpressive buds, there was barely enough THC to get you high, and the flavour wasn’t much better. The best option at the time was the now-iconic Lowryder, a ground-breaking strain that started off as the shunned stepchild of breeding, before eventually becoming a cannabis wunderkind.

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Even still, autoflowering strains were often written off as weed for beginners—nothing for serious cultivators. Fast forward to today, and the autoflowers of old are almost unrecognisable. The next-gen autos on the modern market are capable of churning out hefty yields of flavourful flowers rich in THC. In fact, some autos rival photoperiod plants when it comes to potency, boasting THC levels well into the 20% range. How’s that for a comeback?

What Is The Height Of An Autoflower?

Just like photoperiod strains, the height of autoflowers can vary. That said, autoflowers are generally more compact, maxing out at around 1m in height. Rarely will plants exceed 1.5m. This makes autoflowers ideal for those with spatial limitations and those looking to keep their operation clandestine.

Autoflowers — Advantages


Based on the above, it goes without saying that today’s autoflowers boast a lot of advantages. Here is a rundown on everything these plants have to offer.

• You Don’T Need To Change The Light Cycle

After about 3–4 weeks of vegetative growth, autoflowers independently initiate bloom. That means there’s really no way to extend the veg phase; but for many growers, that’s just fine. Because autoflowers aren’t dependent on a specific light cycle, you can just leave them under 18–24 hours of light until harvest. No need to switch your lights for flowering.

• You Can Harvest Autos All Year Long

Because of their short growing cycle and independent flowering, autoflowers can potentially be grown and harvested all year round. Plant a few weeks apart, and you’ll have a perpetual crop to look forward to. Those living in warmer regions may be able to get away with growing autos outside all year.

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• Autoflowers Grow Fast

Unlike photoperiod cannabis, which requires anywhere from 7–14 weeks just to flower, autos move through their entire life cycle in about 55–60 days after germination. As such, autos are ideal for those seeking a fast turnaround, and those trying to harvest outdoors before the bad weather arrives.

Autoflowering Cannabis Grows Fast

• They Are Resilient

Due to their ruderalis heritage, autoflowers are resilient to cold, pests, and diseases. This makes them easier to manage for new growers, and ideal for colder climates. In regions where there is no frost, such as in Southern Europe, you can grow them outdoors even in winter!

• They Maintain A Compact, Stealthy Size

As mentioned, autoflowers rarely reach above one metre, so they tend to fit in any size tent, as well as in cupboards and closets, and on balconies and terraces. This means there is also less risk that your plants will draw unwanted attention. Perfect for stealthy outdoor grows!

How To Grow Autoflowers: General Tips


Autoflowers have a limited lifespan. Unlike photoperiod strains, which you can theoretically keep in veg as long as you want, autoflowers will be ready to harvest at a set time. This also means that they don’t have time to recover from major mistakes or disease. If something goes really wrong, this will adversely affect yields.

Follow these general tips for optimal results when growing autoflowers:

• Choose The Correct Pot Size

If your pots are too small, your autoflowers can’t grow to their full potential, and you will get smaller yields as a result. If the pots are too big, there is a greater risk of overwatering and fungus. 10–15l planting pots are optimal for autoflowers.

• Don't Repot Your Autoflowers

Repotting stresses plants and slows growth. Since autoflowers cannot fully recover in the limited time they have, you should never repot them. Plant your autoflowering seeds in their final pot for best results.

• Use A Suitable Growing Medium

Choose a light and airy growing medium. This way, your plants won’t need to spend too much energy developing and expanding their root system. Faster root growth means they can absorb the nutrients they need sooner and more effectively.

• Don't Overwater And Watch Ph Level

Be careful not to overwater your plants. Due to their smaller size, autoflowers drink less than their bigger photoperiod sisters. It’s recommended to allow the soil in the pot to dry out before watering again. To see whether it’s time to water, lift the pot to check its weight. If the pot feels significantly lighter than after the last heavy watering, you can water. When you do water your plant, make sure to saturate the entire substrate until you get about 10-20% runoff. Watering this way will avoid salt buildup in the soil, which in turn will make your plant grow faster.

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The pH level of your water or nutrient solution is also important. If you’re growing in soil, make sure your water has a pH value of 6.0–7.0. If growing hydroponically, the pH should be 5.5–6.5. If the pH is off, this can lead to nutrient deficiencies and sick plants.

• Don't Go Crazy With Training Techniques

Don’t use training techniques that involve trimming, pruning, pinching, or topping. The only training technique you can confidently perform on autoflowers is LST (low-stress training). This is where you tie down the main stem and branches to encourage lateral growth. This way, you can trick your plants into producing more bud sites, which can benefit your yields. If you do want to perform LST on your autos, you should take care to start early in the vegetative growth phase, as you only have a few weeks to make a difference.

• Be Careful With Nutrients

Due to the generally smaller size of autoflowers, you should also be careful when administering nutrients. If you’re growing in a typical soil substrate, these normally come pre-fertilised with enough nutrients for 3–4 weeks. Said differently, there is a good chance you won’t need to feed your autoflowers during the entire vegetative phase. Although, you may want to consider administering a root stimulator to give them a boost right from the start. This will benefit root development so the plant can take in necessary nutrients.

Even when you do start administering nutrients during the bloom phase, err on the side of caution and give half or three-quarter doses to start, in order to avoid burning your plants. You'll be able to tell that your plants have entered bloom once they start developing wispy, hair-like pistils from their nodes. These white outgrowths will continue to increase in number as buds begin to form, and will eventually turn an amber-brown colour.

How To Grow Autoflowers Outdoors


Growing autoflowers outdoors can be quite easy, as they are generally robust and hardy plants. Stick to the above tips, and you’re already off to a great start.

However, when growing outdoors, there are a few additional factors to consider.

• Pick The Right Spot

Find a nice outdoor space where plants can access ample light. If you’re growing in Central Europe, choose a spot with as much sun exposure as possible. If growing somewhere with plenty of sun and heat, such as the Mediterranean, pick a spot where your plant receives some shade during the hottest part of the day.

You’ll also want to make sure your autoflower is somewhat protected from wind and rain. Moreover, if you’re growing in an exposed area, you may want to consider hiding your plants among companion species so thieves won’t discover them.

• Pick The Right Time

Take care to start your grow at the right moment—not too early and not too late. Check the expected outdoor harvest time for your strain and count backwards so you know when it’s best to get started. Planting too early could mean a risk of frost, and planting too late comes with the risk of your harvest falling victim to mould. If you have a greenhouse, you can use this to shield plants from bad weather while still exposing them to sunlight.

How To Grow Autoflowers Indoors


When growing autoflowers indoors, most of our general tips apply. However, things can get just a bit more technical.

• Provide Plenty Of Light

These days, you won’t have trouble finding a suitable indoor grow light, as even good LED grow lights are now rather affordable. Of course, with autoflowers, you don’t need to worry about switching your light cycle. Many growers keep their lights on an 18/6 (18 hours of light and 6 hours of darkness) or 20/4 light schedule. Some even grow under 24 hours of light, but keep in mind that this will drive up energy costs.

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• Make Sure Your Plants Have Enough Space

Although most autoflowers will remain compact, you should still make sure to consider the dimensions of your grow space so you can ensure proper ventilation and light coverage.

• Get Rid Of The Smell With A Filter

If you’re growing indoors, the scent of your flowering plants could become a problem. You’ll want a filter to get rid of the smell. Fortunately, many grow tents are already equipped so you can easily add a carbon filter to the exhaust system.

When To Harvest An Autoflower

When To Harvest Autoflowering Cannabis

Most autoflowers will be ready to harvest anywhere from 50–70 days after germination. But don’t just mark your calendar, as determining the best time to harvest is a bit more sophisticated.

You’ll know if your buds are ready to harvest by checking the trichomes on your cannabis plant. Trichomes are near-microscopic “knobs” on the buds that produce a resin rich in cannabinoids and terpenes. Under a loupe, trichs look like tiny mushrooms with a small head.

As buds develop and mature on your plants, the trichomes will change colour from clear, to milky, to amber-brown. With a loupe or a small handheld microscope, you can take a good look at them. Here’s how to “read” your trichomes for an optimal harvest.

Trichome Colour Guide For Harvest Time

  • All trichomes clear: Your cannabis is still far from harvest, with some weeks to go.
  • Most trichomes milky white, some clear ones left: Nearing maximum THC production; may still need a week or two.
  • Most trichomes white with ~15–20% amber-brown: Time to harvest. Buds harvested now are thought to best express the traits of a specific strain.

Tip: You don’t have to harvest all your buds in one go. It’s likely that the topmost colas will be done before the bottom branches, so feel free to chop some earlier than others.

Happy growing!