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 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. 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 autoflower cannabis plants.
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 conditions are like.
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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 autoflowers 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, autoflowers 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.
Autoflowers 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.
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Signs Your Autoflowering 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 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).
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.
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.
As your plants approach the ideal time for harvesting, 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.
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 for how many weeks it takes from germination 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 autoflower weed plants, 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.
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. 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.
Effects of Harvesting your Autoflower 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.
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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.
Autoflower 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 autoflowers, 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.
FAQs On When to Harvest Autoflower Marijuana
You’ll know your autos are ready for harvest by checking their leaves, trichomes, and water intake. Learn more about growing autoflowers in this guide.
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.
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.