Although intense trichome production is not necessarily a sign of a plant’s high psychoactivity, growers use this key indicator to determine when to harvest cannabis. We have all been there, our first grow, week 8, wondering if the plant is ready to chop. Fortunately, most seed breeders include the harvest time for their strains and it is a pretty reliable guide to follow. There are times when this guide isn’t available or on some rare occasions you may run into a slow flowering phenotype of a strain you already grew. Whatever the case you should learn to check the plants yourself so you can harvest when the plant is perfect for your particular needs.
A small magnifier or jewellers loop will work perfectly, one with a built-in light is even better. They can be purchased for under $20 online with a minimum of 25x magnification. By utilizing this inexpensive tool you can fully assess the development of your glandular hairs or trichomes. Capitate glandular hairs with legs should be considered; their colour changes depending on the variety and age of the plant. In most varieties, the heads of glandular hairs are initially transparent or yellowish. Gradually they become cloudy and opaque when the amount of THC in them is maximum, and THC is just beginning to degrade (break down). Regardless of the initial colour of trichomes, it is quite possible to notice the colour change as the plant matures.
Some people wait for about half of all secretory cavities (capitate glandular hairs with pedicles) to become opaque, which indicates the maximum level of THC in the product. Of course, nothing tells you better than how you feel – so try samples of different ages to determine the optimal harvest time for your strain. Simply cut a bud or two at different stages near the predicted harvest time.
By waiting for half of all glands to darken, you maximize the THC content of the weed, but the higher amounts of THC will degrade products such as cannabinol and CBD. Therefore, many people who are growing for medicinal purposes prefer to harvest while most of the secretory cavities are transparent. You will have about 2 to 3 weeks to work with when deciding the ideal time to harvest.
| Green Arrows | Clear (transparent) Trichomes |
| Yellow Arrows | Cloudy (opaque) Trichomes |
| Red Arrows | Amber Trichomes |
How Trichome Colour Influences When to Harvest Cannabis
Some growers prefer to harvest when the trichomes are mostly still clear to give a more cerebral high. Others prefer to harvest their weed well after their trichomes have gone cloudy and most of them have turned amber. This later harvest will give the user a more relaxing high. This is at the sacrifice of some of the plant’s THC content. Ideally, if you are growing your cannabis to harvest THC then try to hit the sweet spot where most of the trichomes are cloudy, some are still clear and very few may have turned amber already. Happy Growing and bountiful harvests.