The Flushing Cannabis Myth – Busted
The value of flushing tends to be hotly debated by many growers with some stating that the same thing can be achieved through curing the harvest correctly. Others might tell you that flushing means starving the crop of vital nutrients and, as a result, quality and yields suffer. I tend not to take a dogmatic position on this one other than to say, what published scientific research that has been done on flushing Med, where comprehensive tissue testing was conducted between two flushed crops and a control (not flushed), concluded:
“6.2 FLUSHING NUTRIENTS FROM GROWTH MEDIA
The practice of flushing is a current common industry practice but there is no evidence in published literature of its effectiveness in reducing nutrient concentrations within the bud or even whether or not this is a desirable result. After testing the nutrient concentrations from each treatment from three separate experiments, there were no significant differences in nutrient levels between any treatments within each experiment. This result showed that the intended purpose of flushing to reduce nutrient concentrations within the bud has no effect. “
To summarize this study:
Flushing occurred over the last two weeks of production when the nutrient solution was replaced with water (no nutrients) during routine irrigation events. Another flushing method was to apply an additional 10L of water without any fertilizer to the plant over two irrigation events at the start of the two-week period of water only irrigation.
3 separate crops were given different treatments. The first irrigation treatment was the ‘control’ which was the standard irrigation procedure used in the facility. This treatment has irrigation events every 2 to 3 days. The second irrigation treatment termed ‘mild-stress’ was an irrigation event applied every 2 days, and the third irrigation treatment termed ‘moderate-stress’ was an irrigation event applied every 3 days.
While flushing had no effect on reducing tissue nutrient accumulation between flushed crops and control (a crop that wasn’t flushed), flushing didn’t reduce yields or quality (THC percentage). However, nor did it improve quality with regards to THC percentage.
Flushing, as a result of these findings, may help growers to reduce input costs (i.e. running water is cheaper than running water and nutrients).
Thus, as flushing is such a controversial, debated subject I’m going to exit stage left and let time and the emerging science of medical research do the talking (it’s a brave new era).
Download research paper here …..
 Jonathan Stemeroff. Irrigation Management Strategies for Medical Cannabis in Controlled Environments. Master of Science Thesis. The University of Guelph. November 2017. Retrieved 9/7/18 https://atrium.lib.uoguelph.ca/xmlui/bitstream/handle/10214/12125/Stemeroff_Jonathan_201712_Msc.pdf?sequence=3&isAllowed=y