What Causes Differentiation in Cannabis Flower Samples

In general we know a plant can have " extreme variation in potency, not just between plants, but even between samples taken from the same plant. This reflects the fact that, unlike other manufactured drugs, cannabis is a natural product whose potency is dependent on multiple factors, such as species, method of cultivation, time of harvest and grower expertise." (  NZ Drug Foundation Staff ( 2 May 2010 )Mythbusters: Cannabis potency. Retrieved from https://www.drugfoundation.org.nz/matters-of-substance/november-2010/cannabis-potency/). 

It's because of this variation we can see up to an 10-15% variance from top to bottom on a single plant. In fact a single 1 gram sample can have a 1% potency difference from the the top of the 1 gram flower to the bottom. This is why we homogenize our samples when they come into the lab to get the best representation of what is submitted. 

All of this variation is why we would expect to see a slight to significant difference from R&D to Regulatory testing based on the representation of the whole batch for the R&D test. the more closely that resembles the overall batch the tighter the numbers should be between the two tests. This won't always result in the tests exactly mirroring each other, but it should be close to 1.5-2.5% ± difference, and this is based on what we had seen in 2018 when we also had field duplicate testing and how the results reflected one another. 

Another way to look at it also is to consider the possible variation of a plant its self of 8-10% then if we took even just 1 gram per a pound in say a 10 pound batch we would take a total of 10 grams that are expected to match that of 4,450 which still is not a significant enough subset to completely encompass all of the possible batch variability within a guaranteed 1.5-2.5% percent. 


Some of the factors that cause increased variation.

For example for an indoor facility factors to consider would be evenness of canopy, penetration of light in the canopy. Growing style plays a factor smaller plants tend to be more consistent due to the above factors. For an outdoor grow the same things must be considered, strategies such as spacing, trimming and training the plants to grow so that light can reach all branches equally more or less will be an important factor. This among other factors such as disease or stress pressure (hot spots) in a grow. Watering differences between plants based on drip system line pressure fluctuations,length of the run for the pump to push, or hand watering inconsistency. To include other environmental and biological factors.


One study conducted to obtain a value for the amount of sample needed to produce a representative sample of a batch or field of Hemp concluded with "A main objective of the study was to estimate the sample size necessary for routine control tasks. But the particular THC distribution found in this study made a parametrical approach to estimate necessary sample sizes impossible. Any apparently homogeneous hemp field may contain a serious number of plants behaving irregularly, with respect to their THC values. Therefore, a representative sample will be rather big. A sample size of 50 plants is fixed by EU regulations (VO (EG) 1177/2000) for routine analysis, and bigger samples are collected where results are not clear. When the sample size is smaller than desired, conclusions based on the data generated are limited.(Mechtler, K.Bailer, J. and De Hueber, K. 2004Variations of Δ 9-THC content in single plants of hemp varieties. Ind. Crops Prod. 191924.)

Another great read coauthored by a majority of our own research department staff
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Ryan C. Lynch, Daniela Vergara, Silas Tittes, Kristin White, C. J. Schwartz, Matthew J. Gibbs, Travis C. Ruthenburg, Kymron deCesare, Donald P. Land & Nolan C. Kane (2016) Genomic and Chemical Diversity in Cannabis, Critical Reviews in Plant Sciences, 35:5-6, 349-363, DOI: 10.1080/07352689.2016.1265363 https://www.tandfonline.com/doi/full/10.1080/07352689.2016.1265363?scroll=top&needAccess=true

Steep Hill is one of the only cannabis testing labs world wide that also has an extensive Research and Development Department. 

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