Humans have cultivated cannabis for a very long time. Still, due to cannabis prohibition policies, many longtime cannabis growers have had to operate in the shadows out of fear of prosecution. That has, in turn, limited cannabis cultivation research and the sharing of useful cultivation techniques and strategies.

Thankfully, things are changing now that the legal cannabis industry is spreading and demand for cultivation-focused research is increasing. Cultivation ‘tips and tricks’ that have been handed down by generations of cultivators within the unregulated legacy industry are now being investigated by scientists to determine if they actually have merit.

One such technique is using pre-harvest mechanical stress, or ‘mechanical wounding,’ on cannabis plants. For years, cultivators have used mechanical stress on plants to improve the overall quality of the harvest. Pre-harvest mechanical stress and its impact on cannabinoid and terpene production were the focus of a recent study conducted by researchers at the Institute of Soil Water and Environmental Sciences at the Volcani Institute. The study’s findings were published in the journal BMC Plant Biology.

“Mechanical-wounding stress is traditionally used by legacy cannabis growers under the belief that it enhances production of cannabinoids, the cannabis-specific therapeutic metabolites. However, this common notion was not tested scientifically and lacks empirical validation. Therefore, the present study evaluated the hypothesis that wounding-stress stimulates secondary-metabolite production in cannabis, and has a potential to regulate the therapeutic chemical composition.” the study’s authors wrote.

The study specifically focused on two mechanical stress techniques. The first is ‘stem-splitting,’ in which cultivators slice the plant’s main stalk right before harvest. The second is ‘leaf-wounding,’ in which growers damage the plant’s fan leaves.

“To evaluate this hypothesis, we investigated the impact of two wounding-stress practices common in traditional cannabis cultivation, stem-splitting and leaf-wounding, on secondary-metabolite production and plant physiological function. The stress was imposed pre-harvest, at the stage of intense secondary-metabolite biosynthesis. Plants were exposed to two stem-splitting treatments (applied 7 and 11-days pre-harvest), and three leaf-wounding treatments (applied 7 and 11-days pre-harvest, with two wounding intensities on day-7).” the researchers stated.

“The results revealed mechanical-stress stimulation of cannabinoid and terpene production, thus supporting the hypothesis. Two major cannabinoids THC and CBC, increased in response to leaf-wounding 11-days pre-harvest, but not by the other wounding treatments, supporting an interaction between wounded organ and timing of wounding. Stem-splitting 11-days pre-harvest increased concentrations of many sesquiterpenes, whereas leaf-wounding affected only a limited number of compounds, demonstrating an organ-dependent response.” the researchers determined.

“Taken together, the results reveal that cannabinoid and terpene biosynthesis are affected by wounding-stress in an organ, timing, and stress-intensity dependent manner. The differential effects on cannabinoids, terpenes, and individual compounds in each chemical group suggest that mechanical damage affects cannabinoid and terpene biosynthesis at distinct points of regulation downstream of the shared GPP (geranyl diphosphate) precursor.” the researchers concluded.