Flushing hemp plants before harvest may be unnecessary

The results of a new research study published this month show that flushing the plants before harvesting does not improve the quality of hemp flowers. The results seem to contradict the widely held belief that flushing the plants improves the flavour and combustibility of the dried cannabis flowers.

In common, though not universal, cultivation practices, hemp growers stop fertilising their plants one to two weeks before harvest to improve the quality of the final product.

“Flushing is important because it removes excess nutrients that are left in the plant,” explains Danny Danko, senior cultivation editor at High Times. “So it helps with the flammability of the flower by washing out excess salts and nutrients.”

However, in the experiment conducted by RX Green Technologies, a manufacturer of cannabis nutrients and other cultivation products, researchers found that participants in a blind test tended to prefer hemp flowers that had not been flushed before harvest.

To conduct the experiment, growers at RX Green Technologies’ research and development facility in Colorado grew hemp plants of the Cherry Diesel variety in a coco-based medium. During growth, the plants were fertilised with the company’s brand of nutrients. Four groups of 12 plants each were subjected to different flush times as harvest approached. Each group of plants was flushed for either zero, seven, 10 or 14 days.

Flower samples taken the day before harvest were analysed for essential plant nutrients. Overall, there was no significant change in the mineral content of the cannabis flowers as a result of the different flushing treatments.

After harvesting, the plants were cured and analysed for final cut flower weight, terpene and THC concentration. Laboratory analysis revealed no significant differences between the different flush treatments in terms of flower yield, THC potency or terpene content.

Samples of cannabis flowers that had been subjected to the different flushing times were also distributed to experts from the hemp industry so that they could evaluate them in terms of smoking properties and flavour. Dr Stephanie Wedryk, head of research and development at RX Green Technologies, says she wasn’t sure how the experiment would turn out.

“I didn’t know what to expect,” Wedryk says. “I had talked to some farmers I knew, and all of them had experience with testing flush times and not flushing, and all of them had only negative experiences when they didn’t flush.”

Flushing hemp plants shows no benefits

However, when analysing the data from the blind tests, the researchers discovered that participants preferred the flavour of the flowers that had not been flushed at all, even though the duration of flushing had no overall effect on the flavour, smoothness of the smoke or colour of the ash. In the study’s findings, RX Green Technologies writes that the study indicates that there is no benefit to flushing marijuana flowers to improve taste or consumer experience.

Wedryk says that while she doesn’t think growers should overhaul their practices based on a single study, she believes growers should be open to trying new things.

“I would definitely recommend that growers try things out and find what works best for them. I spoke to a farmer at the event who doesn’t flush and he is very happy with his product,” Wedryk explains. “Everyone has their own unique system and there are so many different components that go into growing. What works for one grower because of their particular circumstances may not work for another.”

Danko agrees, pointing out that growers who are careful not to use too much fertiliser may need little or no flushing time for their crops.

Flushing is an extension of the fact that most people over-fertilise their crops, says Danko, advising farmers to fertilise their crops only lightly, in many cases at lower rates than recommended by nutrient manufacturers.

“It’s always easier to increase nutrient levels if you find a deficiency than to remove nutrients if you’ve overfed,”

Danko still recommends flushing crops before harvest, but supports efforts to test widely held beliefs in a controlled scientific environment. Wedryk agrees, explaining : The more research that comes out in hemp, the more we have to question some of the things we thought we knew and find out if they’re still true or if it’s a new time.

Wedryk says RX Green Technologies is planning further research into common cultivation practices, although she declined to give any details.

How to flushing cannabis plants before harvesting ? What is flushing and what are its benefits can be found in this article.