The window for optimal harvesting is much shorter for autoflowering cannabis due to its short flowering time.

You'll need to pay close attention and harvest at just the right time if you want maximum yields of dense, trichome-coated buds.

Harvesting too soon results in smaller yields and less developed trichomes, reducing potency potential.

On the flip side, waiting too long can cause buds to deteriorate and lose potency.

So, when is the optimal time to harvest your prized autoflowering plants?

In this article, we’ll show you the best methods for telling when your Autos are ready to harvest. We'll also share some detailed pictures so you know what to look for. 

Key Takeaways

  • On average, autoflowering cannabis is ready to harvest 8-12 weeks after germination.
  • To get the exact time to harvest your autos, check the pistils and trichomes for signs of maturity.
  • The pistils (small white hairs) should be 75%-90% brown before harvesting
  • Trichomes (tiny, sticky resin glands) should be 70% cloudy for a balanced high
  • Leave your trichomes to turn 70% amber if you want a more sedative/body-high

How to tell when your autoflower plant is ready to harvest

1. Look for mostly brown pistils

The small white hairs on cannabis buds are called pistils.

As buds mature, pistils change colour. They usually turn from white to cloudy and eventually to dark brown.

By regularly checking pistil colour as buds develop, you can judge the best harvest time.

What Pistil colours Mean:

  • Mostly white pistils - Too early to harvest
  • About half brown pistils - Wait a bit longer
  • 75-90% brown pistils - Harvest now for best quality
  • Over 90% brown pistils - Harvest immediately!

Checking pistil colour is an easy, free way to help guide harvest time.

However, we also recommend checking your trichomes for an optimal harvest window.

2. Look for cloudy trichomes

Trichomes are tiny, hair-like crystals that grow on cannabis plants. Trichomes help protect cannabis plants, but they also produce the compounds that give cannabis its effects - like THC and terpenes.

Trichomes start growing when cannabis plants begin to flower. Trichomes start off clear, but as they mature, they get more cloudy in colour before turning amber - you need to wait for this amber colour before harvesting.

Here's a simple guide on what to look for in your trichomes

  • Clear colour - Too early to harvest
  • Cloudy white colour - Getting close, cannabinoid levels rising
  • Amber colour - Peak THC. Harvest now for THC/head high
  • Dark amber/brown - Some THC breakdown, CBD rising for body high. 

It helps to use a magnifying glass or microscope to look closely at trichomes. Digital microscopes can connect to a computer. This allows you to save images week-to-week to compare development.

What do you need to do before you start to harvest?

1. Flush before harvesting your autoflower

The most important thing is to 'flush' your autoflowers for at least a week before harvest. This sounds worryingly technical, but all it means is to cease providing your plants with any nutrients and just give them plain water.

Doing this ensures that the plants use up all the sugars and proteins they are storing. If you forget to flush your plants, the resulting weed will have an unpleasantly harsh taste.

How long you flush your plants before harvest varies according to the growing medium - there is plenty of more detailed advice about this subject online - but one thing is for sure - flushing weed is essential for a smooth smoke, especially if you have fed your plants with non-organic fertilizers.

You can tell that the time is right for flushing by looking at the leaves - if they start to turn yellow at the tips, you're good to go.

2. Trim large fan leaves

Experienced growers often choose to trim large fan leaves in the period before harvest to allow closer access to all the side branches and their leaves and buds.

Exceptions when it comes to harvesting autoflowers

1. Harvesting an autoflower early

Sometimes, you may want to harvest early, and there can be excellent reasons for doing this. If your crop is affected by mould, damaged plants, or other pests, it may well be advisable to harvest as soon as your plants start flowering despite the lower THC content.

We don't advise harvesting early unless you are sure that the trichomes have begun to cover the plants with bulbous heads.

Many growers like to test a few early buds, and this is a good idea if you aren't worried about wastage, as it is highly likely that these first flowers will not have had enough time to develop the required THC and cannabinoid for a satisfying smoke.

2. Harvesting an autoflower late

A late harvest often results in an autoflower crop that induces stronger feelings of relaxation and sleepiness, commonly referred to as 'couch lock.'

The crop may well have less THC, but with careful drying, it is certainly possible to achieve a great smoke, and, of course, many people prefer cannabis with higher levels of CBD for medicinal use.