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What is the Best Time to Harvest Cannabis?

Created by
JoshuaHolt JoshuaHolt
Added 21 August 2020

This guide is about choosing the best time to harvest your cannabis plants. We've got some great tips to help you decide when it's time to cut those fresh buds.

When is the Best Time to Harvest Cannabis

THC Bomb by Stick from Grow Diaries, on harvest day.

Introduction: Why wait?

The best time to harvest cannabis depends on how you plan ahead. Whether you are growing indoors or outdoors, there are many different circumstances that can affect a plant's life cycle. Harvesting your plants at the right time will determine their effect and flavour, and mainly relies on you.

Many growers, and especially beginners, often get impatient with their grow. Buds can look so inviting as they reach the end of their cycle, and you may be thinking about chopping them early. As tempted as you might be, there are some things you should know first that may help you resist cutting your hard work too early.

Cannabis Plant Ready For Harvest

It is worth it to wait those extra few days before harvesting.

It would be a shame to ruin your previous efforts so sometimes it is better to wait just those extra few days. You will be rewarded for your patience and end up with a much more satisfying product.

We want to show you how to tell if your cannabis plants are ready to harvest. This article was written to give you some ideas on what to look out for. Let's dive in.

Different Strains: The Cycles

There are lots of strains of cannabis. Different genetics means cannabis plants will grow and develop at different speeds. Flowering cycles range from as low as 6 weeks (indica dominant) to up 15 or 16 weeks (sativa dominant). Choose your strains and check how many weeks of flower they need to mature.

Here we have put together a small list of 8 different strains with their flowering times to give you an idea.

 Indica (%)Sativa (%)Flowering (weeks)
Girl Scout Cookies (FastBuds)60406
Gelato Auto (FastBuds)45556-7
Green Poison (Sweet Seeds)70307-8
White Widow (Royal Queen Seeds)01009
Jack Herrer (Seedsman) 0 100 9-10
 Laughing Buddha (Barney's Farm) 40 60 10
 Shogun (Royal Queen Seeds) 3070 11
 Super Silver Haze (MSNL) 0 100 12-14

Industry grows are producing at a fast rate so growers regularly choose strains with short flowering times. Most growers prefer strains that flower in 7 or 8 weeks because they require less maintenance. A flowering time of 8 weeks also means a grower can get 4 or 5 harvests per year depending on their set up.

Some strains, like Durban Poison are ideal for growing outdoors so their harvest time will depend on the seasonal changes. Sativas are often grown outdoors because they can grow so big. Have a look at this massive outdoor plant that is ready for harvest.

Outdoor Plant Ready For Harvest by Dalemac from Grow Diaries

Outdoor plant ready for harvest by Dalemac from Grow Diaries.

Check the schedule for the strains you are growing. You can also connect with other growers to find out how growing your strain went for them.

This will give you an idea of how long it takes to flower but consider that your growing environment can affect the cycle of a plant.

Tip: Whether you are growing indoors or outdoors, it is a good idea to group your plants into their different strains. Labelling the pots with the name and date helps a lot, and you won't forget which plants are which.

Flushing

Flushing is a very important part of any plant's life. Flushing removes any excess nutrients that might be stored in the plant or in the growing medium. Not doing so will result in a harsh burn and flavour. You won't end up with much more bud if you keep pumping it full of nutrients until you harvest, so do not skip this step.

You will have a good indication of when the right time to flush is because leaves will start to turn yellow. The plant is giving you signs that it is preparing to end it's annual cycle.

Be careful you don't mistake early signs of yellowing as a sign that a plant is ready to flush. Yellowing early on during the flowering cycle could mean your plant is deficient. The following grow is an example of this.

Yellowing Leaves Could Mean Deficiency

Deficiencies during the flowering cycle can force your plant to mature early.

During the growing process, you may have used nutrients or fertilizers. Although they are generally necessary for a plant while it is growing, these need to be flushed out so the final product is as clean as possible.

To flush your plant simply finish it's feeding schedule and then give it only water until you harvest. Flushing a plant for 2 weeks before harvesting will leave you with a much tastier, more pure herb.

Flushing Helps to Remove Excess Nutrients

Flushing is an important part of any grow cycle.

A cannabis plant will stop drinking water at some point, meaning it is no longer trying to live. Once this happens, it has stopped trying to grow and is not absorbing any more. If you notice during flushing that your plant is drinking less than usual it a very good sign it is nearly ready for harvest.

Remember these 3 things when flushing your plants

  • Finish your plant's feeding schedule - leave enough time to flush
  • Give plants only water for the last 2-3 weeks of flowering
  • Don't over water - they only need as much as they can drink in one day

Trichomes

The trichomes on the plant are what we normally look at to see if a plant is ready for harvest. The trichomes are very small and can be found covering bud sites and leaves as a plant flowers. They can look like very tiny mushrooms, with a stem and a ball shaped cap.

Trichomes give the plant their stickiness and contain most of the goodness we love about cannabis. The plant's terpenes can be found in the trichomes, and are what gives cannabis it's lovely smell. You will notice how much stronger this gets as the plant develops it's bud.

Check the Trichomes to See How Your Cannabis Plant Develops

During flowering, trichomes start to grow in large numbers.

It is strongly recommended that you get yourself a handheld microscope so you can take a close look at the trichomes. This is actually really fun and interesting to do because you can clearly see all the details on the surface of the bud. Being able to see the development of these trichomes will help you judge when is the right time to harvest.

You might already be seeing lots of trichomes and be wondering if your plant is ready. If the trichomes on your plant are still clear or look like glass, then your plant needs more time to develop. Give it another few days and check them again.

  • If the trichomes are turning a golden/amber colour or going cloudy, your buds are ripe and probably ready to cut.
  • Don't wait too long otherwise the THC (Tetrahydrocannabinol) will start to break down.
  • When you can see a lot of these trichomes it is a sign the plant is maturing and reaching it's peak.
  • Use a microscope of at least 30x zoom or a magnifying glass.

Cloudy Trichomes Means it's Time to Harvest

Zooming in with a microscope allows you to clearly see the trichomes.

Tip: You can also use a camera to zoom into the trichomes. It won't be as good as a microscope but if you have a decent camera, even on your phone, you may be surprised at what you are able to see.

Pistils

Another way to tell if your plants are ready is to check the pistils. They give the same signs as the trichomes and will usually turn amber. This can vary from strain to strain, so you may want to check with another grower who has grown the same strains you are growing.

If the pistils are still white and pointing up then you need to wait longer until you see them ripen. Once they start darkening and curling in, you are getting close to harvest day.

White Pistils on Cannabis Plant

Lots of white pistil hairs is a good sign and means a cannabis plant is still developing its flowers.

It's normal that your plant's pistils will change colour first on your top buds as these usually mature before buds lower down due to being closer to the light source. You want to wait until at least 50% of the pistils have changed colour.

If you notice your plants have stopped producing pistils and 60-70% look ripe, think about harvesting soon. This will be more or less the optimum range if you are looking to maximise THC content.

Brown, Curling Pistils Signal Harvest Day is Near

A cannabis plant is nearly ready for harvest once its pistils are brown and curling inwards.

This method of checking is useful if you don't have a microscope to zoom in on the trichomes. However, check the trichomes if you can, because some strains have different coloured pistils or might not change colour when they are ready to harvest. 

This grower is in week 6 of flowering and should wait a couple more weeks until harvest. Notice how only about half the pistils have changed colour.

Best time to Harvest Outdoor Cannabis

Growing outdoors means your plants are subject to exterior conditions that can affect the length of the flowering cycle. Much of it depends on the region you live in and the climate you experience there.

You will learn more about the conditions of your area with every grow you do, so don't give up! Weather can be unpredictable but can also do wonders for your garden.

Large Outdoor Garden in the Northern Hemisphere

Outdoor plants can be very rewarding but also require your attention so you choose the best day to harvest.

The hours a plant receives under the sun can change how long it will need to spend in flower before it's ready to harvest. Outdoors, you have less control over the plant's growth and nature will affect how flowers mature. 

Timing is very important so you should be checking your plants daily towards the end of the flowering cycle. 

You need to make sure you harvest your crop before the first frost hits. Plant matter will start to mould or rot as temperatures decrease below 15°c (59°F). If you plant too late into the spring, your plants may not grow big and strong enough before flowering begins, in the end leaving you with smaller harvests.  

5 tips to get the best harvest time outdoors:

  • Choose strains that suit your growing environment.
  • Germinate seeds inside at the end of winter/early spring.
  • Check the sun cycles in your region before planting.
  • Sow outside when temperatures don't drop below 15°c.
  • Harvest before first winter frost.

When leaves start to turn yellow a plant is showing signs of maturity. This is the beginning of the harvesting phase as the plant begins to die and use up it's remaining store of nutrients. This is not to be confused for early yellow/browning of leaves, which could be related to a deficiency.

If you do notice your leaves changing colour during the vegetative phase or early in the flowering stage, it is likely they have a nutrient problem.

Normally growers will harvest their outdoor plants from mid September to mid November. In the northern hemisphere, this is as the autumn equinox arrives and the days start to become shorter again. After you notice leaf yellowing, you can tell if they are ready by checking the pistils and trichomes, as we mentioned earlier. 

Best time to Harvest Indoor Cannabis

Growing indoors gives you much more of a clear idea as to when you will be harvesting. Having full control over the amount of light means you know more or less when your plants will be ready.

Plants that receive the correct amount of light will flower in approximately the same amount of time stated by the breeder, depending on conditions. Remember that there are many variables that can affect your plant's growth, so it's best to harvest when they look ready.

Strawberry Lemonade at 8 weeks by Wachsemilian on Grow Diaries

Strawberry Lemonade at 8 weeks by Wachsemilian on Grow Diaries.

Most indoor strains are feminized, meaning they will flower in a set amount of time after the light hours are dropped to 12. Because you are in control of the light hours you have the possibility to experiment more freely with different harvest cycles.

Indica dominant strains flower much faster than sativas. They flower in about 7-8 weeks after the light schedule is flipped to 12/12. So long as you made a note of when you put them into flower you will know when to start flushing in preparation for harvest day.

It is common for the top parts of a plant to ripen before lower parts because they are closer to the light. One thing some growers like to do is to cut off the top buds and leave lower buds on for a few more days. The plant will push whatever energy it has left into those remaining buds and they will also have more light on them. 

GreenMachine from Grow Diaries shows off his trichome covered plants 2 weeks before harvest.

Harvesting your plants in the morning is the best. Chemical activity in the plant is at it's highest in the first couple of hours of the day. You also won't disturb other plants in your grow room by working during the dark hours.

Tip: Writing up a calendar to know exactly how many weeks your plants have been in flower is a great way to remember when you will need to harvest your plants. It is also helpful to keep a diary so you can keep track of each plant or strain you have.

Effect vs Flavour

There is a common discrepancy between growers about when is the perfect time to harvest. Some believe that harvesting earlier gives you a slightly sweeter taste with just enough potency. Others might prefer trying to harvest when they can get maximum psychoactive effect. Then there's those that want to get 'stoned'.

In the end it all comes down to personal preference. We recommend you stick with one strain through multiple grows so you can discover what works best for you.

The content of THC is changing quickly as a plant ends it's cycle. As the THC starts to break down, it converts into CBN (cannabinol). This is beneficial for some, and can come with it's own medical benefits such as treating pain, arthritis or insomnia. CBN rich weed will produce a harsher smoke, but some growers prefer more of a body high and so will cut their plants towards the end of the harvesting window. 

Super Snowy Bud Showing Lots of Trichomes

Trichomes are what contain most of cannabis' unique flavour.

The effect of THC is more psychoactive. Of course, the effect will also depend on the strain, and whether it is more indica dominant or sativa dominant. To achieve the most psychoactive effect you will want to concentrate on harvesting when your plant is at peak THC level.

Brown Amber Pistils

Maturity

Effect/High

Flavour

<50%

Too early

Low potency

Slightly Sweeter

50%

Beginning of harvest period

Mellow high

Normal

60%

Reaching optimum level

Slightly Psychoactive

Ripened

70%

Peaking THC content

Potent/Psychoactive high

Full

80%

Peak THC content

Potent high

Flavour starts breaking down

>90%

THC starts to break down into CBN

Stoned/Sedative effect

Harsh

This chart is only a general look at how different percentages of brown pistils can indicate potency and flavour. We advise you to try out different harvesting times and see what you like the most!

Harvesting Early

If your crop is failing for whatever reason, you may need to harvest early. This is a decision you will have to make based on the problems you are facing. It is never a nice thing to have to scrap all your plants but sometimes it is the best solution.

Harvesting Early is Sometimes the Best Solution

Choosing the right harvest day will determine the quality of your weed.

Bug infestations or fungus in your garden can spread quickly, so to avoid things getting worse it is a smart idea to accept the loss and start again. You do not want these pests to multiply because it could become a constant problem in your growing environment.

Pesticides and fungicides are not recommended during the flowering cycle as they massively affect the taste of the final product. Most products on the market are chemical and synthetic so you would not want to be smoking these.

Conclusion

After you have spent so much time caring for your plants, it would be a shame to get impatient and harvest them early. However, feel free to experiment with this as you may find new flavours or highs in your favourite strains. You can even cut off small buds at different stages during harvest to test out what you like best.

Don't leave your plants for too long after the harvest window has begun, otherwise your weed won't be as potent and will start to lose it's aromatic flavour. We'd love to hear what you think about harvesting times, so drop us a comment below!

External references

Cannabis, Cannabinoids, and Sleep: a Review of the Literature. Current Psychiatry Reports. - Babson, Kimberly & Sottile, James & Morabito, Danielle. (2017) 

Cannabis Species. - B. Singh, Ram Avtar Sharma. (2020)

Cannabinoid synthesis and accumulation in glandular trichomes of Cannabis sativa. Journal of Acupuncture and Meridian Studies. - Kim, Eun. (2020) 

Hot Summers in the Northern Hemisphere. Geophysical Research Letters. - Zheng, Jiayu & Wang, Chunzai. (2019) 

This article was updated August 2020.






Comments

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*When you check your trichromes don't look at the trichromes at your leaves because they develop much faster. Look at the trichromes on the flower! Don't look at the "pistils" because your plant can be ready to harvest but shoot new "pistils" or the "pistils" are all amber but the trichromes not ready. Growdiaries common....