When to harvest autoflowers

For marijuana growers interested in growing autoflowers, there are a few things you should be aware of to ensure that you maximize their potential.

Just like with photosensitive cannabis plants, knowing when to harvest autoflower cannabis is an art that can make or break your plants’ yield. 

The good news is that autoflowers since they are not dependent on light cycle or local climate for their internal clock, leave less room for error with timing the harvest.

When you read a strain review online for an autoflower, you’ll usually see an estimated harvest time so you can tell when my autoflower is ready to harvest.

This timing is even more likely to be correct than with photosensitive strains. Let’s take a look at how to know when to harvest autoflowering cannabis plants.

growing autoflower cannabis plants
growing autoflower cannabis plants

Growing autoflowers

If you’re reading this, you might not know what autoflowers are, to begin with. 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 darkness usually determine when a marijuana plant will enter its flowering phase.

Autoflowers, however, will enter their flowering phase no matter what the light cycle conditions are like. 

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

For growers in certain climates, this might not seem like such a big deal.

But many growers will tell you that it is a big deal, partly because autoflower strains have a shorter lifespan overall.

This means they will be harvested much sooner than your average photoperiod plant, which can be useful for outdoor growers in colder climates or growers in warmer climates who want to get two harvests out of one summer.

Although not their main feature, autoflowering cannabis come with additional benefits as well. For example, they are shorter in stature than other cannabis strains.

This makes them easier to grow in any setting. For example, people growing indoors will not need so much indoor space to allow their plants to thrive.

People growing outdoors will be able to keep their plants in a more discreet location. 

Autoflower strains are also more resilient to pests and other possible issues that may arise during the grow season.

This makes them easier for beginners to grow, but it also is a handy feature for even the most seasoned of veterans.

To get the most out of your grow, you need to start with the best cannabis seeds! Shop my store for high-quality autoflowering seeds.

bergman holding autoflower plant

Buy Autoflower Seeds

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Signs your autoflowering cannabis plant is ready for harvest 

So, when is an autoflower strain ready to harvest? It’s important to pay attention to the different signs your plants will show you.

Like any photoperiod plant, many signs can point to your autoflower plants being ready for harvest.

The main observations you should make are of the fan leaves, the trichomes, and the water usage of your plants.


Autoflowers that are nearing harvest time will start to have yellowing leaves.

If you begin to notice your mature plants getting leaves that are turning yellow, start planning to flush them for two weeks or so (see below for more on flushing).

Yellowing leaves of autoflowering cannabis plant
Yellowing leaves of autoflowering cannabis plants almost ready for harvest

If you’re starting to notice something more dramatic than that —

namely, that the bigger leaves have begun falling off the plant, then you have already reached the point where your plants should be harvested immediately.


The trichomes are another great way to determine whether your autoflower marijuana plants are ready to be harvested.

The three aspects of the trichomes you should pay attention to are their quantity, their color, and other details about their appearance. 

Milky trichomes
Milky trichomes have the highest levels of THC

Trichomes hold the most CBD and THC, which most growers are trying to maximize when harvesting their marijuana plants. The more trichomes there are, the better.

The color of most of the trichomes should be milky white, which will indicate that they have the highest level of THC possible.

If you want a heavier smoke, you can wait a little later until a third or a half of the trichomes have turned amber in color.

Water usage

As your plants approach the ideal time to harvest, they will begin absorbing less water than before. Test the top layer of soil under your plants.

If it is damp when it would normally be dry, the harvest time has likely arrived.

Because the lifecycle is coming to an end, the plant no longer needs the water and nutrients that would sustain it.

Water usage
Cannabis plants will absorb less water as they approach harvest time


One of the easiest ways to check in with your plants’ harvest readiness is to read the grow guide or reviews of the autoflower seeds you are growing.

When you select and order seeds, there should be plenty of grow information for that particular strain.

Within that information should be a timeline or time to harvest for how many weeks it takes from germination to harvest and seed to harvest.

Check that, do the math, and see if you have surpassed this timeline. If you have, it’s a good indication that you should likely harvest the plants now.

Flushing before harvesting your autoflower 

What is flushing

Flushing” is a strategy that can improve your harvest quality.

Of course, to plan ahead, you’ll need to know when to harvest weed plants from seed to harvest, so do your homework well before your plants reach their flowering phase.

Flushing entails feeding your plants only water rather than including nutrients in the water like you normally would.

Flushing your autoflowers before their harvest time will help rid the plants of any residual chemicals that you definitely don’t want in your harvest.

Ideally, the water will have a pH level of 6.0 to 6.8 if you’re growing in soil or 5.5 to 6.5 if you are growing hydroponically.

Flushing Autoflowers
Flushing Autoflowers

When to flush

Begin flushing two weeks before you plan to harvest your autoflower marijuana plants.

If you don’t do it early enough or aren’t sure of when to harvest autoflower cannabis until it’s too late, you might miss the window in which you can responsibly flush your plants.

Watch the trichomes; once a few of them have begun turning milky, it’s time to start flushing.

For hydroponics, start flushing a maximum of one week before harvest.

and for other mediums, such as coco coir or rockwool, one week will also do the trick. For soil grows, however, two weeks is ideal. 

When not to flush 

If you are growing in organic, amended soil, 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 will only absorb as many nutrients as they need, so they won’t take in too much right before the harvest.

What happens if you harvest your autoflower too early? 

If you don’t time your harvest perfectly, you will have some differing results. If you harvest them too early, you might have taken down the plants before reaching their peak THC levels.

However, if you harvest them just early enough, you will get them right in the sweet spot: at the peak level before the THC has begun to deteriorate.

Learn more about timing your harvest perfectly with my free harvesting mini guide!

It’s important to note that if you harvest your buds too early, it’s not ideal, but it’s also not 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 some rough conditions are on the horizon,

it might be better to harvest now than to wait for heavy rains, winds, or frosts. Even if you don’t have the most THC, it will still be usable.

Why your marijuana leaves are turning yellow
Why your marijuana leaves are turning yellow

Effects of harvesting your autoflowers too late

While harvesting your marijuana plants too early could mean that the THC hasn’t yet peaked, harvesting it too late is also not ideal.

However, this also depends on your preferences. Some prefer a later harvest because it increases CBD levels while lowering THC levels.

Other cannabinoids can also rise in levels during this later stage,

all of which will lead to a more body-focused, sedating effect.

For people dealing with issues of pain or insomnia, this could be the ideal time. Marijuana seeds high in CBD are ideal for beginners because most are bred with hemp plants.

They also grow strong, resilient, and quick to harvest.

High CBD Seeds

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Don’t wait too long to harvest your marijuana plants, even if you want more CBD and a more sedative high.

At some point, the CBD and other cannabinoids will also begin to deteriorate,

which would make the buds far less than ideal.

Autoflowering cannabis is beneficial for many reasons,

and it’s certainly something worth looking into if you want a shorter life cycle for your marijuana plants.

To maximize your autoflowering cannabis, make sure to harvest the buds at the right time.

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

Happy growing!


FAQs on when to harvest autoflower marijuana 

How do I know when to harvest my autoflowers?

You’ll know your autos are ready for harvest by checking their fan leaves, trichomes, and water intake. Learn more about growing autoflowers in this guide

When should I start flushing my autoflowers?

If you’re growing in soil, start flushing your plants 2 weeks before the intended harvest date. If you’re growing in another medium, including coco or rockwool, begin flushing one week in advance. For hydroponics growers, one week or less will do.

What if I harvest too early/late?

If you harvest your marijuana a little early, they will have higher THC levels. If you harvest them a little later, they will have lower THC but higher CBD, making for a more sedative high. Read more about harvesting in this guide

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Robert Bergman


Robert Bergman is an Amsterdam-based marijuana grow expert who has years of experience from small grows to massive operations ... See profile

16 comments on “When to harvest autoflowers”

  1. Oh I forgot my soil is Foxfarms Happy Frog mixed with ocean forest but my Nutes are advanced nutrients Sensigrow and now Sensibloom and I have used Earth Juice Hibrix twice

    • Hi Zev,

      Thanks for the additional information as well! We appreciate you sharing this 🙂

      Happy growing,

  2. I am growing Afhgan Autoflower from ILGM. One plant has the most buds and the hairs are turning brown- so I assume I should start flushing soon as the buds are the fattest I have seen them. I do not have a microscope so will just wait till more pistils turn brown as only 25% of them are, but the other plant is strange in that many leaves are now yellow (But that container is also 50% smaller than the other plant) but the pistils are only just starting to turn brown. I will likely start to flush in another few days to a week for 2 weeks.

    • Hi Zev,

      Thanks for your comment! Sounds great 🙂

      Definitely keep us posted on how the crop turns out!

      Happy growing,

  3. Last year I grew some RED HOT CHERRY and some how a couple buds produced seeds about half dozen or so not including the half dozen I didn’t catch that ended up in joints. Well this year I was going for 2nd gen and somehow the seed I planted ended up turning into an autoflower how , what happened ?

    • Hi Jim,

      Thanks for your message. That’s really rather odd as the autoflowering gene tends to be recessive. There may have been some auto genes in its lineage that somehow came through. Definitely weird though.

      Kind regards,

  4. Okay, my question is: If I am using organic soil and fertilizer/plant food, I don’t need to flush the plants before harvesting, correct?

    • Hi Vicki,

      Thanks for your message. Its less necessary, but still recommended nonetheless. Any type of fertilizer may affect the taste of your buds.

      I hope this clears it up!
      Kind regards,

  5. Purchased seeds from you Different strains. some seed Never took some did. our last up bringing 2 of the Do’se Do popped 1foot heigh there Flowering. we are out doors small amount. The rest are doing good

  6. My method for germination has been to put my seed in the middle of a paper towel, fold it over, and dampen it with water, put that into a zip lock bag of some sort, seal it, and put it in my clothes drawer (a cool dark place). Open it Once a day to let in fresh air and Re-dampen if needed. Within 1 1/2 to 3 days, you should see it sprout. So far, (going on 10 seeds) this hasn’t failed me once.

  7. Hi Robert.
    I have 2 Gorilla Glue autos and 1 is way closer to harvest than the other.
    Would love to send you pics as a first time grower, so I dont ruin what I spent so much time cultivating.
    If that’s cool……let me know via email.
    Thank yo,

  8. Got a question. I’ve got grasshoppers hatched in my area from my dirt. Tried poison to kill. But theyve built resistance. I???

  9. I have purchased seeds from you and they have been in water for five days and have not sprouted out. Please advise.

    • It’s a genetic thing with autoflowers. You could try, but i think they will just ignore it. If it is feminized, yes, you could send her back to veg state.