When to Harvest Autoflowers – The Ultimate Guide


For marijuana growers interested in growing autoflowers, there are a few things to keep in mind to ensure that you are maximizing their potential. Just like with light sensitive cannabis plants, knowing when to harvest autoflower cannabis is an art that can increase or decrease the yield of your plants.

Learn how to harvest autoflowers

The good news is that since autoflowers are not dependent on light or local climate for their internal clock, they leave less room for error when harvesting. When reading a strain review for an autoflower online, you will usually see an estimated harvest time. It is even more likely that this timing is correct than with photosensitive strains. Let’s take a look at how you know when to harvest autoflower cannabis plants.

Growing autoflowers

If you’re reading this, you may not initially know what autoflowers are. Autoflowers come from a clever combination of cannabis ruderalis and other strains. The main difference between these hybrid strains and other “normal” marijuana plants is that autoflowers are not photoperiod plants. In other words, the hours of light and dark usually determine when a marijuana plant will enter its flowering phase. However, autoflowers will enter their flowering phase regardless of the lighting conditions.

Download my free Grow Bible to learn how to grow autoflowers!

For growers in certain climates, this doesn’t seem like such a big deal. But many growers will tell you this is a big deal, also because autoflowers have a shorter overall lifespan. This means they are harvested much earlier than your average photoperiod plant, which can be useful for outdoor growers in colder climates or growers in warmer climates who want two harvests out of one summer.

While this is not their primary function, autoflowers offer additional benefits. For example, they are smaller than other cannabis strains. This makes it easier to grow in any setting. For example, people who grow indoors don’t need as much indoor space for their plants to thrive. People who grow outdoors can keep their plants in a more discreet location.

Autoflowers are also more resistant to pests and other possible problems that can arise during the growing season. This makes it easier for beginners to grow, but is also a handy feature for the most seasoned veterans.

To get the most out of your growth, you need to start with the best seeds! Buy high quality autoflowering seeds from my shop.

Buy autoflowering seeds

Sign Your autoflowering plant is ready for harvest

When is an autoflower strain ready for harvest? It is important to pay attention to the different signs your plants are showing you. As with any photoperiod plant, there are many signs that your autoflower plants are ready to harvest. The most important observations to make are the leaves, trichomes, and water consumption of your plants.


Autoflowers approaching harvest time have yellowish leaves. If you notice your mature plants getting leaves that are turning yellow, plan to flush them for about two weeks (see below for more information on flushing).

By the time you notice something more dramatic – namely, the larger leaves falling off the plant – you have already reached the point where your plants should be harvested right away.


The trichomes are another great way to tell if your autoflower marijuana plants are ready for harvest. The three aspects of trichomes to watch out for are their amount, their color, and other details about their appearance.

Trichomes contain most of the CBD and THC that most growers try to maximize when harvesting their marijuana plants. The more trichomes there are, the better. Most trichomes should be milky white in color, which indicates that they have the highest THC content possible. If you want a heavier smoke, you can wait a little later for a third or half of the trichomes to turn amber.

Water use

As your plants near the ideal time to harvest, they will be absorbing less water than before. Test the top layer of soil under your plants. If it’s damp, when it would normally be dry, harvest time has likely come. As the life cycle comes to an end, the plant no longer needs the water and nutrients it would receive.

Timed coordination

One of the easiest ways to check that your plants are ready for harvest is to read the growth guide or reviews of the autoflower seeds you have grown. When selecting and ordering seeds, there should be enough growth information for that particular strain. Within this information should be a schedule for the number of weeks it will take from germination to harvest. Check this, do the math and see if you have exceeded this timeline. If so, this is a good indication that you should probably be harvesting the plants now.

Rinse before harvesting your autoflower

What is rinse?

Flushing is a strategy that can improve your crop quality. Of course, in order to plan ahead, you need to know when to harvest autoflower weed plants. So do your homework well before your plants reach their flowering stage.

Flushing just feeds your plants with water instead of absorbing nutrients into the water as they normally do. Flushing your autoflowers before harvest clears the plants of chemical residues that you definitely won’t need for your harvest. Ideally the water has a pH of 6.0 to 6.8 if you are growing in soil or 5.5 to 6.5 if you are growing hydroponically.

When to rinse

Start flushing two weeks before your planned harvest of your autoflower marijuana plants. If you don’t do it early enough, or aren’t sure when to harvest autoflower cannabis until it’s too late, you may be missing the window of responsibly flushing your plants. Watch the trichomes; Once some of them have started to turn milky, it’s time to start rinsing.

For hydroponics, start flushing no more than a week before harvest. For other media such as Coco Coir or Rockwool, a week is also sufficient. However, two weeks are ideal for the soil to grow.

When not to rinse

If you are growing in organic modified soils, you don’t need to flush as the nutrients were naturally in the soil to begin with and there are no chemicals to flush out. The plants only take in as many nutrients as they need so they don’t take in too much just before harvest.

What happens if you harvest your autoflower too early?

If you don’t plan your harvest perfectly, you will get different results. If you harvest them too early, you may have degraded the plants before they hit their THC peak. However, if you harvest them just early enough, you will get them right at the sweet spot: at their peak, before the THC starts to deteriorate.

Find out more about the perfect time to harvest with my free mini-guide for harvesting!

It’s important to note that harvesting your buds too early isn’t ideal, but neither is it the end of the world. Sometimes it makes sense to harvest earlier even if it wasn’t your plan. If you check the weather and harsh conditions are looming on the horizon, it may be better to harvest now than wait for heavy rains, winds, or frosts. Even if you don’t have the most of the THC, it can still be used.

Effects of picking your autoflower too late

If you harvest your marijuana plants too early, it may mean that the THC has not yet peaked. Harvesting too late is also not ideal. However, this also depends on your preferences. Some prefer a later harvest as it increases CBD levels while lowering THC levels. Other cannabinoids can also spike at this later stage, resulting in a more body-focused, calming effect. This might be the ideal time for people dealing with pain or insomnia.

High CBD marijuana seeds are ideal for beginners as most are grown from hemp plants. They also grow strong, resilient, and harvest quickly. Buy seeds with high CBD content in my shop now.

Buy High CBD Seeds

Even if you want more CBD and a more calming high, don’t wait too long to harvest your marijuana plants. At some point, the CBD and other cannabinoids will also start to deteriorate, which would make the buds far less than ideal.

Autoflower cannabis is beneficial for many reasons, and it’s definitely worth checking out if you want a shorter life cycle for your marijuana plants. Make sure you harvest the buds at the right time to maximize your autoflowers.

It takes practice and learning to grow marijuana like a pro. Our blog will help you answer all your growing questions.

Have fun waxing!


FAQs on when to harvest autoflower marijuana

How do I know when to harvest my autoflowers?

You know your cars are ready for harvest by checking their leaves, trichomes, and water intake. For more information on growing autoflowers, see this guide.

When should I start flushing my autoflowers?

If you are growing in soil, start flushing your plants 2 weeks before the planned harvest date. If you are growing in any other medium, including coconut or rock wool, start rinsing a week in advance. For hydroponic growers, a week or less is enough.

What if I harvest too early / too late?

If you harvest your marijuana a little earlier, they will have higher levels of THC. If you harvest them a little later, they will have lower THC levels but higher CBD levels, resulting in a comforting high. For more information on harvesting, see this guide.

I Love Growing Marijuana Founder Robert Bergman is a marijuana growing expert who loves to share his knowledge with the world. He combines years of experience, from small extensions to massive operations, with a passion for growing. His articles include tutorials on growth … [read more]



Robert Dunfee