The Science and Art of Harvest Timing
As we continue our deep dive into cannabis cultivation, last week’s discussion on trichome biology and cannabinoid production provided a foundation for understanding how cannabis resin is produced. Now, we shift focus to one of the most crucial decisions in cultivation—when to harvest.
Harvest timing determines not only the potency and effects of cannabis but also its flavour, aroma, and overall quality. Trichome maturity, environmental factors, and strain-specific characteristics all play a role in finding the perfect moment to cut down your plants. By considering recent research, we can refine traditional grower wisdom with scientific precision, ensuring each harvest meets its full potential.
Understanding Trichome Maturity and Cannabinoid Changes
Trichomes, the microscopic resin glands on cannabis flowers, are the ultimate biochemical factories responsible for producing cannabinoids like THC, CBD, and terpenes. Over time, these trichomes undergo visual changes that signal cannabinoid maturation and determine the plant’s effects.
Clear Trichomes: These are immature and contain low levels of THC. Harvesting at this stage results in a weaker psychoactive effect. Some plants can even develop these clear trichomes during the vegetative stage. A sign of high oil concentration. Mostly these types of strains are bred for extractions.
Cloudy/Milky Trichomes: This is the ideal harvest window for peak THC levels, ensuring maximum potency and a euphoric high. When harvesting at this point it is important to note that as the trichomes ‘finish off’ after harvest they will peak at the best time and you will be set to cure them. Trichomes always mature further after harvesting.
Amber Trichomes: As trichomes age, THC degrades into CBN, producing more sedative effects. Some growers harvest at this stage for a more relaxing experience. If you are growing a more hybrid strain and wish to give a more sedative feel to the strain then having some amber trichomes will assist in this. But note that the flavours and aroma will be affected by this. More than 20% amber trichomes would be considered a very late harvest.
According to a study on trichome maturation and cannabinoid biosynthesis, genetic expression changes as flowers mature, influencing cannabinoid conversion pathways. This means that harvesting at the right time isn’t just about visual cues—it directly impacts the plant’s chemical profile and effects.
Strain-Specific Maturity Windows
Different cannabis strains mature at different rates, making it important to observe trichome development rather than relying solely on a generic timeline.
Indica-dominant strains: tend to mature faster, usually within 7-9 weeks of flowering, making early trichome observation crucial. It is easy to miss the optimal harvest time with indica strains as they mature very quickly, day-to-day. I recommend harvesting when there are milky trichomes and perhaps a hint of amber. Don’t do for 10% amber on indica-strains. They end up being flat and not as potent as expected.
Sativa-dominant strains: often take longer, sometimes up to 12-14 weeks, meaning that cloudy trichome formation may occur later in the cycle. Growers tend to get impatient and harvest these too early. Resulting in grass-like smelling flowers as well as very ‘weak’ THC sativas.
Hybrids: vary based on their dominant traits, requiring careful monitoring.
Understanding your plant’s genetic background allows for precise harvest planning, maximizing the desired effects and cannabinoid profiles of your cannabis flowers.
The Jewellers Loop
This tool like many others has been repurposed for us. Now a staple in all committed growers’ arsenal. The jeweller’s loop is essentially a magnifying glass growers use to get up close and personal with the trichomes. Allowing them to inspect specific spots on the flowers for more accurate trichome maturity identification. These days, growers have digital versions that allow up to x1000 zoom, they sync with your smartphone… It has truly become a niche on its own within the harvesting tools kit.
Where do you check to see?
There are so many ways to skin a cat. Let me start by saying this. I have seen people check at various places on the plant for harvest readiness. Personally, I harvest the entire plant all at once so I tend to look towards the middle sections of the plant and I will judge by looking at a bract in this area of the plant. Knowing that above there are more matured trichomes than below the section I inspect so If I see a solid milky concentration here I know my tops are hitting roughly 5% amber. My personal sweet spot.
The Role of Environmental Factors in Harvest Timing
Environmental stressors can accelerate or delay trichome maturation, affecting cannabinoid production. According to research on trichome morphology, light intensity, temperature fluctuations, and humidity levels all contribute to the final quality of cannabis resin.
High-intensity light increases trichome density but may also prematurely degrade THC if exposure is prolonged. We can see this on very hot days towards the end of our harvests. The plants do not like extreme heat, and the trichomes will start turning amber because of this. Growers in high-heat areas tend to grow under shade netting to avoid this degradation of their flowers.
Fluctuating temperatures can stress plants, influencing terpene volatility and aroma retention. Some growers can use this to their advantage, as we mentioned in our previous blogs. Growers can stress plants by introducing extreme cold, causing extra chemical responses out of their plants.
Humidity control is crucial; too much moisture near harvest can lead to mould growth, while overly dry conditions can degrade terpenes. A well-maintained environment ensures optimal resin preservation and peak cannabinoid content at the time of harvest.
Terpenes and Harvest Timing
Terpenes, the aromatic compounds responsible for cannabis’s signature scents and flavours, follow a different developmental timeline than cannabinoids. While cannabinoids like THC and CBD continue to increase in concentration as the plant matures, terpene production often peaks just before full cannabinoid maturation. This is because terpenes are more volatile than cannabinoids, meaning they evaporate more easily when exposed to heat, oxygen, or prolonged plant stress.
During the later stages of flowering, the plant continues to synthesise terpenes, but these compounds can degrade if the plant is left to mature too long. Overripe cannabis flowers may still retain high THC or CBD levels, but excessive time on the plant can lead to terpene oxidation, which dulls the aromatic profile and alters the effects. For example, myrcene, a terpene known for its sedative properties, degrades faster than beta-caryophyllene, which is more stable. Growers aiming for a full-flavoured, aromatic product should time their harvest to capture peak terpene expression before extended trichome darkening and cannabinoid breakdown.
One of the best strategies to preserve terpenes while still achieving cannabinoid maturity is precise environmental control in the final weeks of flowering. Reducing light intensity slightly in the last days before harvest can help minimise terpene loss due to excessive UV exposure. Additionally, harvesting during cooler parts of the day (such as early morning or evening) can reduce immediate terpene evaporation. Studies indicate that cultivars bred for high terpene retention may benefit from earlier harvest windows, where trichomes are mostly cloudy with some clear heads, instead of waiting for full amber conversion. By aligning harvest timing with peak terpene synthesis, growers can enhance the sensory experience of their cannabis while still preserving the cannabinoid potency desired for recreational or medicinal use.
For growers focused on flavour-rich, aromatic cannabis, harvesting slightly before full trichome maturation may preserve more volatile compounds. Consider the fact that when you are smelling the awesome flavours on your plants, these are terpenes that are evaporating or collapsing.
Techniques for Staggered Harvesting
For growers looking to maximize all aspects of their crop, staggered harvesting can be a highly effective strategy.
Upper canopy harvesting: Because top colas mature faster due to greater light exposure, they can be harvested first, allowing lower buds more time to develop. This is an effective strategy for sativa strains, as flower maturity can vary and they can grow much taller.
Progressive harvesting by trichome stage: Some growers prefer harvesting plants at different trichome maturities to produce a diverse range of effects within a single crop. This technique is often used by cultivators that are into extractions. I have mainly seen this done for rosin or bubble hash extractions. Making for unreal, complex flavourful extracts.
Precision and Patience Pay Off
Timing your harvest correctly is an art and a science. By closely monitoring trichomes, environmental factors, and strain-specific traits, growers can ensure their cannabis reaches its maximum potential in potency, flavour, and effect.
With the knowledge gained from this week’s discussion, next week’s blog will focus on flushing techniques. This essential pre-harvest step further refines the quality and smoothness of your final product—or so they say. Is it just more Bro-science? Stay tuned to find out.
Reach us on WhatsApp