What is cannabis?

It goes by many names: pot, grass, dope, draw, hash, weed, Mary Jane,  blow, buds and even broccoli. These nicknames refer to the drug cannabis, which comes from the marijuana plant. But as well as being used as a recreational drug by humans for hundreds if not thousands of years, it's also been put to medical use. It's the cannabinoid chemicals made by the plant, concentrated chiefly in the flowers and seeds, that are responsible for its infamous high, as well as its medicinal properties.

Graihagh Jackson took a trip down to Kew Gardens to meet Deputy director of Science, Monique Simmonds, and learn more about the drug and the plant it is from.

Graihagh - I'm sat, fanning myself underneath a banana tree. I'm shrouded in a fine humid mist and around me is an assortment of beautiful tropical trees and brightly coloured shrubbery. All I need is a piña colada and I might as well be in paradise. Except I'm in London and it's a bleak winter's day outside. Kew Garden has the most incredible array of plants from across the world. Currently, I'm in the iconic Victorian Palm House where all the tropical triffids live. But this is only one of many greenhouses which contain many, many more plants. Ironically though, I'm here to talk about a plant that Kew doesn't have. It's actually illegal for them to grow it and that plant is cannabis.

Monique - I'm Monique Simmonds and I'm the Deputy Director of Science at the Royal Botanic Gardens of Kew. Cannabis is a plant that is found in parts of Asia. There are different species. There's about 3 different species of cannabis but they're actually whats termed chemotypes and they're the ones that vary in the chemical composition. They vary because of environmental conditions but also, people have selected lines that are high in the group of compounds that are often associated with hallucinogen, their activity, and that's the cannabinoid compounds, often called THCs.

Graihagh - While there are only 3 species of the cannabis plant, there are many variations which produce different amounts of different chemicals and these are called chemotypes. This variation can occur naturally but more recently, humans have been selectively breeding them to contain more of a certain chemical called THC.

Monique - It's the chemotypes that are the key here, where they're grown and what they're grown for because of course, traditionally in the west, cannabis was grown as a form of hemp.

Graihagh - So, what's the difference between the cannabis you smoke then and hemp?

Monique - Well, hemp is low in the THC compounds. So, you could grow a field of them and you'd extract very low levels of the active ingredients whereas if you're in parts of Asia, those are traditionally used, it would often be the seeds etc, which were traditionally used in medicines. They all have the higher levels of the active compounds of THCs.

Graihagh - So, what is it in cannabis that gives us this mind altering highs if you like?

Monique - THC which is one of the compounds is often referred to as being associated with its highs. But there's a range of different compounds. There are about 19 compounds that are thought to contribute to the beneficial effects. I will emphasise that the plant has got a long use for benefits for treating different forms of pain also, for affecting depression. Well, we have big challenges at the moment because it's very, very difficult to study the plant because you need to have a license. Because it's being used as a recreational drug for people to get a high, and it can cause really bad effects on a lot of people who do take it, there are negative impacts. It's banned and therefore, there are restrictions on how it can be researched. So here at Kew, what we'd really like to have is more research being done on the chemistry, a better understanding of the use of these plants, the effect that they can have on the body. But it's clear from the work that has been done that they affect different parts of the brain, they had effects on mood, plus also relaxant and on pain relief.

Graihagh - Is it only cannabis that has these compounds that could be beneficial?

Monique - The range of THCs, yes, they are very often restricted and nature often does that. It comes up with a group of plants where they are restricted. And that's often associated with the genes in those groups of plants affecting the biosynthetic pathways that will result in the expression of these compounds. Most likely, the next question is, what role do they play in the plants?

Graihagh - Precisely. I was going to say, it's like a defence tactic?

Monique - We actually don't know exactly the role that they do have. They're known to have a negative effect on insects and one of the activities is antifeedants for a group of insects. But they most likely have other roles in the plant. It's just very difficult to study that. Nature would have evolved them I'm sure for some purposes. It's expensive for a plant to produce these compounds. They must have a role in the plant.

Kat - That's Monique Simmonds, Deputy Director of Science at Kew Gardens speaking with Graihagh Jackson.