I came across this interesting snippet on the Update list:

“A study done by L.G.Cartwright and L.E.Mather of the Department of Pharmacy at Sydney University published in The Australian Journal of Pharmaceutical Sciences in 1972 found that in seven samples of cannabis grown in Australia THC content varied from 0.4 to 11%. The lowest concentration was found in a whole plant grown in a suburban garden in Forest Lodge, Sydney. The highest concentration was found in female flowering tops gathered wild in the Hunter Valley. Other samples contained an estimated THC content of 9.2%, 9.4%, 1.6%, 4.3% and 3%. Climate, temperature and soil were all factors cited as influencing THC content.

This study was reported in the Technical Information Bulletin No. 15, November, 1972 published by the Commonwealth Department of Health to inform the Alcohol and drug field of national and international research. It is a good source for past scientific thinking on cannabis.

This study would suggest that not all the cannabis smoked in the 1960s and early 1970s was of low THC content.”

Nothing particularly surprising there but a useful historical perspective.