Harvesting Hemp Early?

Hi fellas!

As someone diving into the hemp space, I have come across many manufacturers struggling to address the >0.3%THC issue. Some are attempting to prevent this from becoming an issue by harvesting the cutlivars early.

Is there evidence to suggest that THC is produced in the later stages of the plant? Isn’t early harvesting going to drastically affect the CBD production of the cultivar? Wouldn’t flash chromatography in post-processing be the most financially viable method of achieve compliant material?

Thanks in advance!

you seem to have a handle on the problem.

Yes, harvesting early will keep THC numbers lower.
Yes, it will also keep total biomass, and total cannabinoid numbers down.

Is chromatography an economically viable alternative? no clue. it is somethig big pharma tries to avoid where possible. we are essentially @ big pharma at this point.


@cyclopath, haven’t we also seen higher CBD potency when harvested at week seven versus havesting at weeks nine or ten in a particular strain of CBD? Not saying it is true for all CBD plants, but it may be something to look in to. I definitely don’t know how the timing would play out for outdoor cannabis, but I think that some strains have the potential to increase CBD content with earlier harvest. I am sure that with some strains overall processed yield could increase when harvested at just the right (earlier that expected) time. It would require lots of regular sampling and testing, but if one was so inclined and had the time/resources to experiment, I would eagerly appreciate hearing about the results.


As you go out past 6-7weeks, Biomass yield continues to increases. And CBD to THC ratio starts to lean more towards THC.

we’ve gotten 100:1 vs 20:1 vs 12:1 is my recollection

pulling early really has effected my numbers. I am only growing pheno’s that give a fragrant oil when they have to be pulled. This leads to a better oil for us. Hopefully one day these laws will change.

1 Like

Hi @1Lune. Can you elaborate?

We could read between the lines and guess at how your numbers were effected, but quantifying, or even just explicitly stating the direction of that effect, would be more useful for folks reading along at home :wink:

on average, how long have your plants been in flower before you “have to pull”?
How high do the THC numbers go if you let them be?

these “fragrant oil” phenotypes, care to share their names or providence? Are there strains/cultivars/chemovars that you would advise folks to avoid because they make too much THC early?

1 Like

We pulled some cherry early last year at 7 weeks and it was 7.5% Cbd and less than .1% THC. They lab we used did HPLC and I don’t really trust labs on biomass tests. There are a lot of cherry varietals and I am not sure “which one” it is. But the cherry nose on it was amazing at 7 weeks. It was pulled due to labor constraints.

I am definitely looking forward to more standardized genetics so we can make better conclusions. We have a remedy that gets .2+% and 10-12% CBD. It’s just to risky to grow stuff that gets so close without higher ratios on aggregate. I love the limonene on this one… hoping a reworked version is available next year

I think if there was any take away from my last 3 years working on such low concentrations in the biomass, the crude oil tends to give you a better idea of the cannabinoid ratios. I think their are some statistical principles regarding sample size at play here.

I have been growing a decade. I am certainly a novice when it comes to the scale this industry has gone too. When I have some good data worth sharing I totally will :slight_smile:

Stoked to have found this place.


Is this a problem with ground biomass or whole flower?

If its whole flower, typically leaving it on the branch and untrimmed will greatly reduce the cannabinoid % by weight


if you want it done right, do it yourself. get some In House analytics

if you’re planting from seed, you’ll get all kinds of variation, so testing a dozen samples from around the field is advised. Presumably you’ve noticed the variation in your fields if you’ve done this a couple or three times already.

the lab is extracting your biomass to test it. extracting more biomass will give you a better average. extracting more samples will also help.

in a pinch you could perform a pilot extraction on a dozen plants chosen at random and have the lab analyse that, but doing the analysis yourself allows you to get harvest day right rather than just close enough.


GW Pharma has already done the research on this. Most cannabis plants reach their peak cannabinoid:biomass ratio in weeks 5-6. After week 6, you still have the potential of increasing biomass by 20% or more, but you will never produce 20% more cannabinoids in that period You are in the territory of diminishing returns. Harvest time should be mid to late September, no later. Farmers assume more biomass = more cannabinoids, but any of us that have studied nature know that these relations are hardly ever linear. Molecular farming for extraction means finding the peak ratio of the production of that compound, not the overall mass of the plant. But hey, a field full of ripe hemp flowers looks great on Instagram…


Forever Flowering Hemp Farm

Do you have the link to their research

1 Like

Here’s the most relevant study I came across while researching this last summer. It’s also included in OregonCBD’s very informative whitepaper, http://oregoncbdseeds.com/THC%20Content--The%20White%20Paper.pdf

Evolution of the Cannabinoid and Terpene Content during the Growth of Cannabis sativa Plants from Different Chemotypes


Thank you