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Writer's pictureJim Jones

How to grow autoflowers

Updated: Oct 23

Auto-flowering refers to a cannabis trait that allows these special plants to produce buds without needing a specific amount of darkness each day. Autoflowers are not photoperiod (light hours) dependent plants. An internal clock controls the plant’s natural transition from vegetative to flowering cycles. In this autoflower grow guide we will point out all you’ll need to know to get started.


What are autoflowers?

Many of the tools and nutrients you use are the same between autoflowers and other types of cannabis varieties. However, there are important things to know if you’ve never grown an auto-flowering plant. Our guide covering the differences between Autoflower vs Photoperiod plants will give you everything you need to know and the confidence to succeed.

What is Cannabis ruderalis?

Ruderalis is a variety of cannabis that is the foundation behind all modern autoflowering cannabis plants. Ruderalis genes give autoflowers a trait that’s independent of the photoperiod. Since their rise to popularity, the process of breeding autoflowers has become more efficient, offering a wider range of terpene, flavor, and cannabinoid profiles.


Although Cannabis Sativa was classified in 1753, and Cannabis Indica was classified in 1785, the Ruderalis species wasn’t classified until 1924. Naturally, by now, you want to know more. We’ve prepared an excellent primer to get you up to speed with your cannabis ruderalis knowledge.

If you want to know more about Cannabis ruderalis or how it sparked the autoflower movement into gear, read our article on how autoflowers were created.


Why grow autoflowers?

Gardeners will find many reasons why growing autoflowering cannabis seeds can be adventitious. Highlights include not needing to change lighting schedules, shorter seed-to-harvest durations, and easier harvesting. Due to the short vegetative stage, autoflowering plants remain compact, making them ideal for people wondering how to grow cannabis in a small space.

Autoflower grow compared to a Photoperiod grow

The information above clearly shows the differences between autoflower and photoperiod plants

Outdoor growers have the potential for an extra harvest each year by placing autoflowers in the field between the vegetating photoperiod plants. It is possible to have a summer harvest of autoflower cannabis plants and a fall harvest of photoperiods. Depending upon the climate zone, autoflower marijuana plants can be grown all year round, further increasing outdoor yields.


Ruderalis plants have less THC than most of today’s strains. A common question is, are autoflower strains less potent? No, in fact, you can find autoflower strains with over 20% THC on our ILGM website. Autoflower breeders have been crossing ruderalis with traditional strains and refining them over generations. Now we have 100% autoflowering strains. These new autoflower genetics feature the same high cannabinoid profiles as the photoperiod relative.


Each cannabis variety has advantages and disadvantages depending on a grower’s garden space, skill level, and available time. To decide if growing autoflower marijuana plants may be the right variety of cannabis for you, we invite you to check out our article What are autoflower seeds.


Comparison of the leaves between the three main variants of cannabis plants.

Comparison of the leaves between the three main variants of cannabis plants.

How much does an autoflower yield?

Several important factors will impact the final yield of any cannabis plant; autoflowers are no exception. In general, autoflowers will yield less than a photoperiod plant due to their smaller size. A way autoflower growers compensate for lower yields per m2, is in the ability to harvest more frequently than photoperiod growers.


Considering all of these factors, including which genetics you are running (find some of the best autoflower strains in our ILGM store), the average yield will be between 50-250 grams per plant. For more details and to learn how to estimate your harvest accurately, visit our article; how much yield can I expect from a single autoflower plant.

For growers who enjoy knowing all of the details and expert tricks to increase autoflower yields, be sure to read our article on how to maximize autoflower yield.


How to grow autoflowers

With the advantages autoflower seeds can offer growers, many people ask; how easy are autoflowers to grow? They are no more difficult than the average house plant. Autoflowers can be grown by gardeners of all skill levels, but use our Autoflower grow bible and ILGM genetics to get the best results possible.


In the Autoflower grow guides, our team of expert growers has created a surefire manual on how to grow autoflowering seeds to the best of their potential. We’ve collected years of experience and combined it into easy-to-read, comprehendible guides. We cover the differences between growing autoflowers and growing photoperiods. Having this knowledge can support your decision to give autoflowers an opportunity in the garden.

If you are a person who also prefers visual aids in the learning process, you will love our week-by-week autoflower life cycle – with pictures.


Buy Autoflower Seeds

  1. For new and experienced growers

  2. Easy-growing, low maintenance

  3. All popular cultivars


Growing autoflowers indoors

Indoor growers with limited space will enjoy the compact nature of these plants. Growing autoflowers indoors gives the gardener control of environmental conditions and lower pest pressure than an outdoor grower may face. By controlling these two yield-limiting factors, autoflower seeds grown indoors have the potential for larger yields.


How to grow autoflowers in a grow tent is an easy question to answer for anyone who has grown cannabis. A unique advantage autoflower plants offer tent growers is that autoflower plants can flower alongside vegetative photoperiod plants.

Autoflower plants can enter their flowering stage under a number of light schedules, unlike photoperiod plants with their specific light hour needs. This autoflowering trait can help indoor gardeners maximize their footprint.


Growing autoflowers outdoors

Outdoor growers in the right climate zone can plant autoflower plants year-round. This advantage increases overall yields and is a great way to harvest as many strain varieties as possible.

For gardeners who grow a photoperiod crop each season, plant autoflowers between them when your photoperiod plants are moved into the field. The autoflowers will be finished before your photoperiod plants begin to flower. This one trick can double your harvest each year.

You can find that tip and a whole lot more in our guide, How to grow autoflowers outside.


Choosing autoflower seeds

Autoflower seeds are similar to photoperiod seeds. Physically, they look the same in shape and coloring. Both have hard outer shells and use the same germination methods. Autoflower seeds and photoperiod seeds can both be regular, which means they have the potential to produce male and female offspring. Photoperiod and autoflowering seeds can also be feminized, producing only female plants. All ILGM autoflower seeds are feminized.


Super autoflower seeds offer growers the ability to grow full-sized plants but with the advantage of the autoflowering trait. This is a genetic breakthrough for growers who want larger harvests and aren’t concerned with a longer than normal vegetative time for an autoflowering plant. The taste, cannabinoid levels, yields, and growth duration are on par with photoperiod plants, but super autoflower seeds will flower independently of the light schedule.


Taking autoflower clones is counterproductive. Clones are used to extend the life of a plant by taking a cutting, rooting it, and starting the growth clock all over again. Automatic varieties have an internal clock, which is independent of light or any other factors. You can take autoflower clones, but they will flower at the same time as the parent; therefore, making it impractical. Autoflowers are always grown from seed.


Many of your favorite photoperiod strains have been bred with ruderalis genes over generations to reliably express the autoflowering trait. Now, popular strains like Gorilla Glue, Gelato, Runtz, and others can be enjoyed by autoflower growers. To help you choose from the many autoflower seed options available on ILGM, read our list of the best autoflower strains.


What’s the best soil for autoflowers

There are three common mediums for planting autoflower seeds.

  1. Coco Coco gives the grower a wider margin of error with watering, but it has no nutrients, and growers must follow a feeding schedule.

  2. Soil For soil, the three main constituents are sand, silt, and clay. Most bagged soil consists of peat, forest products (shredded wood chips), coco coir, perlite, vermiculite, and other ingredients. There is no sand, silt, or clay in these mixes, so they are called a “soilless potting mix”. Soilless potting mixes are a popular option for growing autoflower seeds. It retains moisture well and often has enough nutrients to sustain vegetative growth.

  3. Living soil The final option would be super soil or living soil systems, which make the most sense if growing in a large bed. When the plant is ready to harvest, chop the plant, leave the rootball, and plant the new plant next to the old one. This type of soil system gets better over time; it is not thrown out after each planting. Help decide which soil system is best for you by reading our article on the best soil for autoflowers.


Most autoflower growers will choose one of the three soil options mentioned above. Unlike photoperiod plants, most autoflower growers do not transplant during the course of the grow. To help you select the right container for your next autoflower grow, read our article on choosing a pot size for autoflowers.


Hydroponics are great for autoflower yields if you know what you’re doing

Hydroponic systems are known for producing explosive growth. Autoflowers do well in hydroponic systems, but there is a larger margin of error with hydroponics and autoflowers. Nutrient imbalance and pH issues can cause stunted growth, which plants need time to recover from. If you stunt the growth of an autoflower plant, you will likely reduce your yield significantly.

Hydro grow box

Example of hydrophonic setup

Germinating autoflower seeds

There are many ways to successfully germinate autoflower seeds. Common methods include germinating in a paper towel, a glass of water, and direct sow. The same techniques used to germinate photoperiod seeds can be used for autoflower seeds. Regarding the germination process, there are no differences between the two cannabis varieties.


The direct sow method happens when a grower plants autoflower seeds directly in soil. This is an acceptable practice, mainly for indoor growers who can control soil temperature. You can learn more about this process and the others mentioned above, in our step-by-step guide on how to germinate autoflowers.


How long do autoflowers flower for?

Autoflower seeds come in many different strains. Each strain and, more accurately, each autoflower seed will have a different amount of time it will grow before transitioning to flower. The autoflower veg time will be relatively similar for each of the strains. Autoflower varieties commonly have a vegetative growth period of 25-40 days.

The same rules apply to the question of “how long autoflowers flower for”? The exact answer will be strain-dependent, but most autoflower plants are ready to harvest 55-65 days after flowering begins. Super autoflower seeds will produce a plant with slightly longer vegetative and flowering times.


How do you know your autoflowers are ready for harvest? You can anticipate what to expect from an autoflower harvest and be prepared by looking at our guide on when to harvest autoflowers. This guide will save you time and hassle by learning a few easy steps to ensure an efficient harvesting process.


Autoflower light schedule

All cannabis plants need light to live, but autoflowers are unique. Automatic plants can flower under a number of light schedules. Common light schedules for autoflowers include 24/0, 20/4, 18/6, and 12/12. However, the right schedule for you will depend on a number of factors. One of those important factors will be a light’s Photosynthetic Photon Flux Density (PPFD) output.


Proper lighting lets plants harness the energy and convert it to food that fuels plant growth. Intense light can deliver more PPFD in a shorter time than a lower-wattage lamp. To simplify selecting a lighting schedule for your autoflowers, we created a guide on finding the best autoflower light schedule.

From seedling to harvest growing time

A scheme which shows the average stages in the growth of cannabis plants

Nutrients for autoflowers

Autoflowers need the same macronutrients and micronutrients as photoperiod plants to sustain vigorous growth. One noteworthy difference is that autoflowers prefer a lower EC when fed. Too many nutrients can shock the roots and stunt their growth.

Organic growers have had success growing autoflowers in living soil beds. This is accomplished by using larger soil masses that are reused each grow. Partially due to the microbial activity and organic materials in the medium, the soil quality improves over time until you no longer need to feed it. If you want to learn how to grow autoflowers organically, please let us know in the comments.


There are many options for which nutrients to use with your autoflowers, but we’ve compiled a list of the best nutrients for autoflowering cannabis. Once you choose which nutrients to use, you must know how much and when to apply it. We’ve got you covered with all of your autoflower questions. Before starting your next autoflower grow, be sure to visit our article highlighting the best feeding schedule for autoflowers


Pruning autoflowers

Should you prune autoflowering marijuana plants? Autoflowers are on a predetermined schedule; if the growth is stalled, this can reduce the final yield. Aggressive pruning can cause stress to the plant, which can divert growth energy into energy that is spent recovering. For this reason, most growers don’t do much pruning on autoflower plants.

Occasionally a grower may top an autoflower plant, but due to the short vegetative time, autoflower plants generally have a compact structure.


Commonly with autoflower strains, the auxiliary branches reach upwards to nearly an even height with the apical meristem. This negates the benefit of topping, which is to create an even canopy.

Not all pruning or training is stressful enough to an autoflower plant that it stalls growth. Removing leaves gradually instead of all at once can reduce the stress induced by their removal. To address this concern and present “best practices”, read our brief article that answers the question “should you defoliate autoflowers“?


Conclusion

Autoflowers have come a long way since the original Lowryder autoflower plant. The ILGM roster of available automatic and super automatic seeds will demonstrate a wide range of choices. Today we have the choice of different terpene and flavor profiles, as well as cannabinoid levels.

Professional autoflower breeders have had decades to refine and stabilize autoflower genetics. Through these advancements, we are now entering the prime era for autoflower cannabis growing.


The information surrounding the growing practices and feeding schedules is widely available to growers of all skill levels. We recommend downloading Robert Bergman’s free download, The Marijuana Grow Bible.

It’s also a great autoflower grow bible. All the information in our free grow guide can be used to grow photoperiod and autoflower seeds.


Autoflowers offer unique advantages to indoor and outdoor growers. Hopefully, this article piqued your curiosity and answered your questions. Take advantage of the autoflower grow guides on this page for further details into a whole range of autoflower-related topics.

Learn all you can; visit our store for autoflower seeds, make your choice, and start your next growing adventure.

Happy gardening!

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