When it comes to growing cannabis, the harvesting stage can be just as critical as the care you put into cultivating your plants. That’s because the date you choose to harvest your flower has a big impact on the THC levels and desired effects of the final product. Let’s take a look at how the harvest date affects THC levels in cannabis.

The Relationship Between Harvest Date, Potency, and Effect

The harvest date you choose has major implications. Cannabinoid and terpene levels can vary significantly within the same cannabis strain depending on when you decide to harvest your plant.

Growers typically harvest cannabis after a 2-month flowering stage. But for different strains, optimal harvest dates can vary from a few days to several weeks. The optimal harvest window will usually coincide with the plant’s THC production peak. Terpene production tends to peak around the same time as THC. The plant will be more potent and flavorful when harvested at this peak.

The best time to harvest will also depend on the effect you’re trying to craft for your customers. Do you want your flower to feel uplifting and stimulating or have a strong sedative effect? Or maybe you’re hoping to provide a calming, less psychoactive experience. If you want the right effect, you need to pay attention to the harvest date.

So how do you decide when your plant is ready?

It’s All in the Trichomes

Trichomes are fine, hair-like appendages that grow on the surfaces of some plant species. In the case of cannabis, the trichomes are where the plant produces all of its cannabinoids and terpenes. Therefore, the optimal harvesting window corresponds to when the trichomes are fully developed.

Harvesting too early results in underdeveloped trichomes. The cannabis flower will be less potent and taste more earthy due to low cannabinoid and terpene levels. Waiting longer to harvest gives the trichomes ample time to develop. But the longer you wait, the more highly intoxicating and sedative your flower will become. This is especially true for indica strains, but even sativa strains can become sedating. Additionally, if you extend the flowering stage too long before harvesting, THC will begin to degrade.

Use an HD digital camera with the macro setting or a hand-held microscope to get a close up look at your plant’s trichomes. Here’s what to look for:

  • Shape: Trichomes with rounded, mushroom heads are developed and contain more THC. Avoid harvesting when the trichomes still have flat heads.
  • Color: Trichome hairs will initially appear clear, then turn milky, and eventually brown or amber. Milky trichomes typically correspond to the THC production peak.


If you want your flower to have the right effects and the highest potency, you’ll need to choose your harvest date carefully. But once you’ve picked the best harvest date for your strain, how do really know the potency? Encore Labs offers a full range of compliance testing for cannabis producers in California, including cannabinoid potency and terpene analysis.