When to Harvest Cannabis for CBD, According to Science

Researchers have figured out a way to grow and harvest cannabis to get the maximize the yield of CBD, according to a study published in the journal Royal Society Open Science.

CBD, or cannabidiol, is an active chemical compound found naturally in cannabis plants. CBD is a hugely popular alternative medicine treatment for a variety of ailments, ranging from joint pain and eczema to depression and epilepsy.

Regardless of scientific confirmation of the effectiveness of CBD at treating these conditions, the demand for cannabinoids is growing, with the global market expected to reach $9.69 billion by 2025, according to the authors.

"CBD distillate sells for $3,000 per kg, while CBD isolate sells for $1,000 per kg," co-author Andrew Hunt, from Thailand's Khon Kaen University, told Newsweek.

cannabis farm
Stock image: A farm of cannabis plants being grown. iStock / Getty Images Plus

The latest research is a collaborative project between Khon Kaen University in Thailand and the University of York in the U.K. Scientists were looking to find out how to grow cannabis for maximum CBD yield.

While CBD is legal in many countries, THC (tetrahydrocannabinol), the compound that gets you high, is usually banned. Therefore, cannabis growers who are producing CBD products need to be careful to keep the levels of THC in their plants to below legal levels.

The authors have investigated how chemical composition changes in hemp at different harvesting times, which is crucial in harvesting as much CBD as possible from cannabis plants and therefore maximizing the crop's value industrially, without increasing the yield of illegal THC compounds.

"In the USA, the legal THC concentration limit cannot exceed 0.3 percent on a dry weight basis in any parts of the plant, seeds or extracts," said Hunt.

According to the paper, a growing cannabis plant undergoes important compositional changes in three different compound classes: essential oils, cannabinoids and lipids.

The authors have found that essential oils and cannabinoids increased in the tops of plants (inflorescencess) until full flowering in the third harvest, before decreasing at seed maturity in the final harvest.

"Initially, as hemp grows, the levels of cannabinoids are low until the plant reaches flowering," Hunt said. "Cannabinoid content then decreases until seed maturity is reached.

"The greatest proportion of cannabidiol was extracted from the tops at full flowering, however a significant increase (63 percent) in the banned psychoactive tetrahydrocannabinol (THC) was observed at this harvest stage as compared to the budding stage of development, where the plant initial begins flowering.

"Harvesting the tops after budding would be preferable due to the high cannabidiol content and low amounts of THC."

This study also demonstrates the presence of phytosterols and wax esters in the leaves, which have been used as blood cholesterol reducing agents, and both cosmetic and personal care products, respectively.

The results of this research may help cannabis farms increase their yields by harvesting the different compounds at different times.

cbd oil
Stock image: a doctor holding a bottle of CBD oil. iStock / Getty Images Plus