Due to countless iterations of cross-breeding, there are now more marijuana flavors than there are colors in the rainbow. Some are piney, some are lemony, and others still can smell like a whole fruit basket. But some strains don’t exactly smell like roses — in fact, the opposite is true in this case. The clearest example is skunk weed, which, as the name implies, smells like an angry skunk.

How can a plant smell like a mammal? It all has to do with terpenes, a class of aromatic chemicals found not just in cannabis, but in many other plants and even some insects.

Secreted in the same glands that produce cannabinoids like THC and CBD, terpenes are aromatic oils that are responsible for the taste and smell of cannabis — but that’s not all that they do.

Research suggests that cannabis terpenes play a considerable role in not only tempering the intoxicating effects of THC, but also creating synergy with phytocannabinoids and even increasing their therapeutic value. For instance, Professor Dedi Meiri and the Israel Institute of Technology are investigating marijuana terpenes as an anti-inflammatory agent to prevent the most severe, life-threatening cases of COVID-19.

There are at least 200 different terpenes in cannabis, although only a handful gives off a dominant aroma. Pinene is responsible for some strains’ pine-like fragrance, while caryophyllene is peppery. The skunky funk of some strains is due to myrcene, an earthy or musky terpene.

While a skunk’s defensive spray doesn’t contain terpenes, it has similar compounds called thiols. When these organic sulfurs mix together, they produce the potent, musky scent that people stay away from — unless it’s marijuana. That’s because skunky strains are also highly potent. In fact, in many parts of the world, the term “skunk weed” has taken on a more generic meaning, describing highly potent pot rather than the aroma of particular strains.

Because myrcene is the most abundant terpene in the cannabis plant, all strains will smell a bit like a skunk, although some strains are certainly more pungent than others. Some of the famous skunky strains include Golden Ticket and Death Star. If you really don’t like the smell of skunk, less smelly strains include Lemon Haze, Alpha Blue, Kali Mist, Orange Bud, and Northern Lights, according to WikiLeaf.

In the future, high-tech growers could infuse marijuana with a variety of different terpenes of their choosing. In 2017, researchers at the University of British Columbia, Canada, sequenced the genomes of various cannabis plants to see what particular genes give certain strains their characteristic flavors. They found 30 terpene synthase genes that contribute to the diverse flavors of cannabis, which could be manipulated to generate more consistent desirable smells. This is already underway in the wine industry for grape genes that encode enzymes for various flavors.