How To Grow Autoflower Seeds: A Beginner’s Guide

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Autoflower genetics have been greatly improved over the past decade and, as a result, have exploded in popularity. Today, these cannabis are easy to grow, produce high-quality buds, and reach maturity in half the time of other cultivars. However, if you’re used to growing photoperiod plants, you may find that the process of cultivating autos is quite different. So, in this article, we’ll provide a complete beginner’s guide on how to grow autoflower seeds.

What Are Autoflower Seeds?

Autoflower cannabis seeds offer many advantages over other varieties of cannabis. Unlike traditional photoperiod cultivars, autoflower will begin flowering regardless of the light cycle. In contrast, photoperiod only start budding if they are exposed to 12 hours of darkness. This means that growers don’t have to worry about having separate veg and flowering rooms when growing auto seeds.

What’s more, autoflower grow much faster than their photoperiod counterparts. In most cases, the plants will be ready for harvest in just 8 to 10 weeks from seed. They’re also much smaller and more compact than most, making them ideal for guerilla grows or micro grows.

With all these advantages, it’s easy to see why so many cannabis cultivators are turning to autoflower seeds to streamline their grows.

How To Grow Autoflower Seeds

Indoors Vs. Outdoors

The first step in cultivating autoflower seeds is deciding where to grow them. Fortunately, these are very versatile and can be grown both indoors and outdoors in a variety of climates.

Indoor growers tend to produce the highest-quality cannabis. That’s because they have complete control over the environment and can adjust the temperature, humidity, and lighting to create optimal conditions for cannabis. The downside is that indoor cultivation requires the up-front investment of lights, fans, tents, containers, and other equipment.

Growing outdoors is typically the easiest and most affordable way to cultivate autoflower seeds. With mother nature in charge, you won’t have to worry about buying a ton of specialized gear. But if you decide to go this route, choose a strain that grows well in your environment and plant the seeds at the right time to avoid frost.

Choose the Right Autoflower Strain

Now that you’ve decided where you’d like to grow, the next step is to choose which autoflower strain you’ll be cultivating. With so many options available nowadays, it can be challenging to determine which seeds to pick.

If your grow area is cool and dry, an Indica-dominant strain may be your best bet. These cultivars have adapted to handle temperature swings and periods of drought. On the other hand, those in warm, humid regions are better off choosing a Sativa-dominant variety, as these are resistant to bud rot and other fungal infections.

No matter what strain you decide to grow, source it from a reputable seed bank with high-quality cannabis seeds. At Greenpoint Seeds, we have a diverse collection of premium autoflower seeds bred from the finest cannabis genetics.

Light Schedule

As mentioned earlier, autoflower plants will start the flowering process regardless of the light cycle; however, choosing the right light schedule can help you save money on electricity bills while maximizing the yield of your plants.

Most indoor growers opt for a 24-hour light cycle or provide their plants with 18 hours of sunlight and 6 hours of darkness. By going with the 24-hour schedule, you won’t have to worry about setting up light timers or turning off the lights manually every day. But you’ll spend more money on electricity each month than with an 18/6 schedule.

Another option is to provide 12 hours of light and 12 hours of darkness. A 12/12 schedule will save you the most money and produce a decent harvest. But, if achieving a large yield is your biggest concern, this light schedule may not be the best choice for autoflower plants.

We recommend using an 18/6 schedule, as it will give the plants a little time to rest, maximize bud production, and save some money on electricity.

Once you’ve determined which light schedule is best, you’ll need to buy a high-quality grow light that’s powerful enough to cover your grow area. The general rule of thumb for LED lights is to provide 40 watts of light per square foot of grow space.

Soil and Nutrients

With lighting out of the way, it’s time to talk nutrients. Providing your plants with the right balance of micro- and macronutrients is one of the most important steps in learning how to grow autoflower seeds. Luckily, autoflowering aren’t too picky when it comes to fertilizers.

Autoflower seeds can be grown in hydroponic and soilless media; however, most beginners will have an easier time growing in premade potting soil that is pH-balanced. If you decide to use soil as your medium, choose a soil mix that is light and airy. Autoflower tend to perform best in fluffy soil that isn’t too nutrient dense.

Even if you buy a soil blend that’s packed with nutrients, you’ll likely need to fertilize your plants at some point. Many growers opt for a simple three-part synthetic nutrient line such as the Fox Farm Trio or General Hydroponics Flora Series. These nutrients have been specifically formulated for cannabis and provide easy-to-follow instructions for the entire lifecycle of the plants.

If you’d prefer to go the organic route, you’ll need to buy some dry amendments to top-dress the soil periodically. Worm castings, compost, kelp meal, and other organic fertilizers can be added to the topsoil to keep the plants healthy and happy. As with synthetic nutrients, there are many pre-made blends of dry amendments that are easy to use for beginners.

pH for Autoflower Plants

If you decide to use synthetic nutrients to fertilize your plants, you must keep a close eye on the pH of your water and soil. These nutrients often cause the pH to change significantly, creating nutrient imbalances in your plants. The easiest way to control the pH is to buy a high-quality pH pen and some pH Up and pH Down solutions.

Like most cannabis plants, autoflower plants thrive with pH levels between 6 and 6.5. So, after you’ve added the nutrients to your water, measure the pH and adjust it accordingly.

Those going the organic route won’t have to worry as much about pH changes. That’s because most organic soils have natural buffers that help to regulate acidity and alkalinity. These soils are also filled with beneficial microbes, which also can help to buffer the pH of the medium. However, even organic gardeners should occasionally check the pH of their soil and water, as some fluctuation is likely to occur.

Training Methods

High- and low-stress plant training methods are great for controlling the height and boosting the yield of cannabis plants. But not all training techniques are ideal for autoflower.

Because autoflowering plants have a very short lifecycle, it is easy to stunt their growth. Once they have become stunted, the yield and overall quality of the buds will be significantly reduced. Therefore, it’s best to use low-stress training (LST) techniques to avoid damaging your plants. When done correctly, LST can serve to boost yields, increase light penetration and airflow, and keep the plants from stretching during the flowering period.

If you’d like to give LST a try, check out our in-depth guide here.

Pests and Diseases

Environmental stressors such as pests and diseases also can stunt or kill your autoflower plants. Therefore, creating an integrated pest management (IPM) routine is essential to keep your plants healthy and happy.

The best way to prevent the spread of pests and diseases is to provide your plants with the optimal nutrients and environment. The healthier your plants are, the better their ability to fend off outbreaks and infections. By keeping the growing area clean, regulating the temperature and humidity levels, and providing a nutrient-rich diet to the plants, you’ll rarely run into issues. And if you do have problems, your plants will be strong enough to recover quickly.

If you encounter pests or diseases, it’s vital to act quickly to resolve the issue before it spreads. A small infestation of spider mites can become overwhelming in a matter of days, so have a plan in place and a supply of organic pesticides and fungicides at the ready.

The Autoflower Lifecycle

The needs of autoflower plants change significantly through their lifecycle. A seedling will have drastically different environmental and nutritional requirements than a fully mature plant. So, let’s take a look at each growth stage to better understand how to grow autoflower seeds.

Germination and Seedling Stages

For autoflower seeds, it’s best to plant them directly into their final container rather than a plant-starting pot. Repotting the plants will expose them to strain which may permanently stunt them. Depending on how large you want the plants to grow, 1.5-gallon to 4-gallon pots will be sufficient for autoflowering plants.

Cannabis seeds typically take 3 to 10 days to germinate. During this time, the seed will open, and a root will emerge from it, eventually becoming a seedling with cotyledon leaves. During this period, you’ll need to keep the medium moist and maintain relative humidity (RH) levels of between 70 percent and 90 percent. You should also avoid placing the plants under a powerful light source or using fertilizers, as they are very susceptible to light and nutrient burns during the seedling stage.

Within a couple of weeks, your seeds will have fully germinated and formed their first set of “true” leaves. At this point, the plants have started the process of photosynthesis and can be placed under a small grow light.

Vegetative Stage

By week three, your plants will have entered the vegetative growth cycle. During this phase, the plants will build the foundation to support their flowers, forming lots of branches and leaves.

At this point, your plants will start demanding higher levels of nutrients than during the seedling stage. Vegging plants require higher nitrogen levels and lower phosphorous and potassium levels. You should also reduce the RH level to approximately 50 percent to prevent the growth of mold and mildew.

The vegetative growth period is the best time to train your plants, as they’ll have a little time to recover before flowering. It’s also the best time to use foliar sprays, as you should avoid spraying the plants with anything once they have started blooming.

Flowering Stage

Within five weeks, most autoflowering will enter the flowering period. During this time, the plants will begin forming small bud sites at the nodes on each branch. If you’re growing regular auto seeds rather than feminized auto seeds, now is the time to determine the sex of the plants and separate the males from the females.

During flowering, you’ll need to reduce the humidity level in the grow room to around 45 percent RH to prevent botrytis from infecting the flowers. You’ll also need to fertilize the plants with higher levels of phosphorous and potassium and lower nitrogen levels to promote bud growth.


Depending on the strain, most autoflowering plants will be ready for harvest within 8 to 10 weeks. At this time, the buds will have fully formed, and the leaves will fade from green to yellow, purple, or red.

The easiest way to tell if the plants are ready for harvest is to observe the pistils on the flowers. If most of them have turned from white to orange or red, the plants are likely fully mature; however, this method isn’t always foolproof.

The best way to determine ripeness is to use a magnifying glass or jeweler’s loupe to observe the trichomes on the buds. When most of the trichomes have turned from clear to amber, your plants are at peak and are ready to be harvested.

Once the plants are ready for harvest, you’ll need to cut them down, dry and manicure the buds, and then cure them for several weeks. This is a critical process that, if done incorrectly, can degrade the flavor of the buds.

For more information about drying and curing cannabis, check out this guide.

How To Grow Autoflower Seeds: Final Thoughts

Well, there you have it: our complete guide on how to grow autoflower seeds. Cultivating autoflowering plants is a relatively quick and easy process that will reward you with tasty, buds that are much higher quality than those found at most dispensaries. And by following the steps outlined in this article, you’ll be able to avoid many of the pitfalls that new growers often encounter.

What are your top tips on how to grow autoflower seeds? Please share your thoughts in the comment section below. While you’re here, don’t forget to shop our collection of regular, feminized, and autoflower cannabis seeds.

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