Question: When to harvest autoflowers?

Growing

Are your autoflowers in bloom and filling the grow tent with their delicious aroma? It must be time to finally get harvesting! But, hard though it is, try and slow down and have a little bit of patience; there are a few things you need to do to maximise the potency and quality of your harvest. And the first thing to do is to read our guide to find out all you need to know about when to harvest autoflowers.

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

  1. Flush before harvesting
  2. Trim large leaves

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 it plain water. Doing this ensures that the plants use up all their 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 fertilisers.

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.

Signs that indicate your autoflowers are ready to be harvested

  1. Observe pistils
  2. Yellow leaves
  3. Usage of water
  4. Curving and drying of smaller leaves

1. Observe pistils

Observe the colour and appearance of the pistils. The pistils are the reproductive organs of the female cannabis flowers. Over time, as the buds mature, the pistils change colour. The exact change varies according to the variety of the autoflower, but they typically start as a creamy white and then progressively darken, often ending in a dark brown shade. So, carefully observing the appearance of the pistils of your cannabis flowers as they grow is an inexpensive and reliable way of judging the best time to harvest.

Look at the approximate percentage of pistils that have changed colour. If most of the pistils are white, it is way too soon to harvest, for example. If just over half of the pistils are brown, it is best to wait for a bit longer. If about 75% – 90% are brown, harvest now, the plant is heavy and ripe, and it is the optimal time for a good quality crop. If over 90% of the pistils are brown, harvest immediately as you may have left it too late!

However, other factors can affect the colour of pistils (changes in temperature and humidity), so it is unwise to solely rely on the pistil method to judge the timing of your autoflower harvest, especially if you are a novice grower. If you are the type of grower who likes to handle and touch the growing flowers, this can also affect the colour of the pistils!

The Trichome Method

Trichomes are microscopic hair-like crystals that cover the leaves and buds of your cannabis plant, and also serve as glands for the production of resin. Trichomes act as a defence for the cannabis plant. Their bitter smell and taste ward off animals or insects that may be tempted to eat the leaves. Both producer and protector, trichomes are one of the most essential parts of the cannabis plant and play a significant role in producing the psychoactive effect for which cannabis is famous.

The word ‘trichome’ derives from the Greek word for hair. Trichomes house the compounds that have become synonymous with cannabis – THC, other cannabinoid and terpenes are all manufactured inside terpenes and start to form as the cannabis plant enters the flowering phase. So you can see that close observation of the development of trichomes is a good way of observing the maturity or ripeness of the weed. Trichomes change colour as they start to develop. They can be clear, white, amber or brown and the colour of trichomes is sometimes used by cannabis growers to determine the best time to harvest.

There are three types of trichomes, and each one is bigger than the last:

  1. Bulbous trichomes – these are the smallest and are challenging to see with the naked eye.
  2. Capitate-sessile trichomes – these are slightly larger and cover the cannabis plant profusely.
  3. Capitate-stalked trichomes – the largest and most potent type of trichome. These are the types of trichomes that emerge during flowering and produce the most cannabis compounds. They can be easily identified as they have a long stalk and are clearly visible to the naked eye.

They initially have a transparent, cut glass appearance, which indicates it is far too early to harvest. Over time, this translucent appearance becomes gradually cloudier or more opaque. This is one of the situations where experience pays off, as it can be quite tricky to tell the difference the first time you observe trichomes, which is why we recommend using a combination of methods. And it is also true that the trichomes of autoflowers do not change as dramatically as those of photo-period plants.

If the trichomes have changed to an amber colour, you haven’t necessarily left it too late, but the effect may tend towards more an Indica buzz rather than an active strain.

However, it is a good idea to invest in a magnifying glass so you can carefully observe your plant’s trichomes. A hand-held one if fine, but you may prefer to get a digital microscope -many models are surprisingly affordable. Use a USB charger to connect it to your laptop or tablet and enjoy a fascinating view of the surface of your plant’s leaves and buds. A significant advantage is the fact that you can save digital images taken from one week or day to the next, allowing you to compare the development of the trichomes easily.

Using these two methods will give you a good chance of harvesting at the crucial window when your cannabis plants have their highest levels of THC before it starts to degrade.

2. Yellow leaves

Formerly green leaves turning progressively yellow from the tips downwards suggests the plant is concentrating all its energies on flowering rather than growing and is one of the signs that the time has come to harvest. When you notice the larger fan leaves start to yellow, you can begin the flushing period. However, be wary if you have used nitrogen fertilisers as they can have a delaying effect, and the leaves may not turn yellow until after the optimal period for harvest.

3. Usage of water

When your ladies take up less water, it is a sign that they are no longer growing and are ready for harvest. This is not an exact science, but if you water your plants and notice that the soil remains moist after a couple of days, it could be time to get the shears out.

4. Curving and drying of smaller leaves

Another change that frequently happens at the same time as reduced water intake is the curling up and drying of the smaller leaves that surround the bud, sometimes known as sugar leaves.

If you notice all of these signs happening at roughly the same time, you can be confident that your autoflowers are ready for harvest or could benefit from waiting for a few weeks more.

Exceptions when it comes to harvesting autoflowers

  1. Harvesting an autoflower early
  2. Harvesting an autoflower late

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.

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