I know things might get confusing with a species and genus having the same name, so if you see something Capitalized, know that is the genus name. Cannabaceae, also widely known as the hemp family, is a relatively small family of flowering plants, including about 170 species (in 11 genera). While cannabis and hemp are what the family is named for, the largest genus in the family is Celtis, which contains around 100 species. Hops (Humulus) is another notable genus in the Cannabaceae family, which is well known to anyone who likes IPA beers.

Humanity has a very long history of using cannabis, over 2,500 years, and has used the common hop (Humulus lupulus) as a bittering agent and preservative in beer for hundreds of years. Genera in the Cannabaceae family are physically diverse, including actual trees (Celtis), metaphorical trees (Cannabis), and vines (Humulus). Despite plants looking quite different, one somewhat common trait among members of the hemp family is that plants are often dioecious, having both male and female plants. Cannabaceae plants also tend to have petalless flowers which are pollinated by wind, not bees or other insects.

  It should come as no surprise to anyone who is a fan of Lagunitas brewery, that they have one of the better articles online discussing the genetic links between cannabis and hops. To sum it up, cannabis and hops are very closely related. How close? Not quite brother and sister close, but like cousins. Lagunitas lays out the history, clearly establishing that cannabis came first, long before hops, which tracks with the known history of human use (we have been using cannabis for nearly 2,000 years longer than hops).

While hops doesn’t have cannabinoids, it does share numerous terpenes with cannabis, most notably myrcene and humulene. Beyond just terpenes, another connection between cannabis and hops are esters. Research has shown that “Fruity smelling esters play an important role for the aroma of hops and beer and they have been characterized as key aroma compounds in different hop varieties.” While a genetic connection between cannabis and hops was long suspected, it was confirmed about a decade ago.

Out of all the plants in Cannabaceae, hops and cannabis are the most alike. Beyond the basics, like a shared method of pollination, both have “resinous glands which contain their active compounds. Hops plants are known for their lupulin glands, and cannabis plants are known for their trichomes.” Given these similarities, it should come as no surprise that there are recipes for cannabis beers online. Medicinal Genomics (MG), a world leader in medicinal plant genomics, notes that Hop Latent Viroid (HLVd, also commonly seen as HpLV and HpLVd) occurs worldwide in hops plants but recently it made the jump to infect cannabis plants as well.

According to MG, “HLVd is a single-stranded, circular, infectious RNA. Similar to viruses, viroids are completely dependent on their host plant’s metabolism for replication. However, unlike viruses, viroids do not have a protective layer, such as a protein coat.” Kevin McKernan, is the CSO and Founder of MG, and recently completed his own study on HLVd, where they tried to intentionally infect various cultivars with it. In their study, McKernan found that the cultivar Jamaican Lion appeared to have some tolerance and was able to keep the viroid confined to its roots and was otherwise asymptomatic.

Currently, it is not known if it was just the particular Jamaican Lion plants in their study with this tolerance, or if it is common to all Jamaican Lion plants. This study gives hope that there could be more cultivars with some tolerance or resistance to HLVd, or at the least, that resistance can be crossbred into other cultivars. An interesting variable they found to be connected to this resistance to HLVd was increased anthocyanin production, offering a potential clue as to where that tolerance came from.

  Dark Heart Industries (DHI), is a major cannabis nursery and genetics company in California. DHI conducted HLVd testing for more than 100 growers across California between August 2018 and July 2021. Their findings shocked the industry, reporting “more than 33% of the tests from almost 90% of the cultivation sites were positive for HLVd [which supports projections] that Hop Latent Viroid affects more than 30% of all cannabis plants.” DHI pegged the annual economic losses from HLVd at around $4 billion for 2021.

Dr. Bryce Falk, Professor Emeritus at UC Davis’s plant pathology department, has called HLVd “perhaps the greatest threat to the legal cannabis industry.” The big risk with HpLVd isn’t to consumers, this isn’t a viroid that can be passed on to people who consume the bud, it is a viroid that attacks the plants themselves and stunts their growth, a process known as “dudding.” MG’s research on Jamaican Lion holds the promise that, in time, we could have a solution to the economic blight of dudding.

  Despite many growers claiming to grow trees, and some cannabis plants being well over ten feet tall, with reports of some topping twenty, the only actual trees in the hemp family are in the genus Celtis (hackberry trees), some can grow up to 90 ft tall. As Celtis is by far the most prevalent genus in Cannabaceae, some sources refer to it as the hackberry, rather than the hemp family, but they are incorrect as Celtis is a recent addition to the already established Cannabaceae family (previously it was a member of the Elm family).

  While every species in Celtis is unique, the leaves of the common hackberry (Celtis occidentalis) are some of the first to yellow in the fall, usually in late September. Many species of hackberries produce small black drupes, the berry in the name “hackberry.” Those berries were used as food by native american tribes and are still used as food by dozens of species of birds and mammals. One thing that makes the common hackberry truly unique among members of Cannabaceae is that, while there are no Cannabis plants native to North America, hackberry trees are, which is a bit of a paradox since hackberry trees evolved from cannabis and hops.

Presently, there is no sign of HLVd infecting any species in Celtis. The diverse Cannabaceae family is clear proof that just because two plants are related, they may not look or act anything alike. Read less