We all know hemp has multiple uses. Its fiber has been used in cordage, industrial and apparel textiles, and paper. Its pulp can be used as insulation material and cement (hempcrete). And its seed is an excellent source of nutrients including essential amino acids and has been used for animal and human feed, such as in granola. The oil extracted from the seeds can be used in salads or personal hygiene products such as body lotion, shampoo, and cosmetics. Biofuel can be derived from the whole plant through cellulose saccharification and fermentation, and because the plant tolerates high-planting density [1], this could be an important future use. Other potential commodities that hemp offers are the production of bioplastics and of high-performance carbon nanostructures for electronics and meta-materials. However, hemp, and Cannabis in general, is well-known for the medicinal compounds that can be extracted from its flower.
So, we have an interesting question… can we have one hemp variety that can be used for all these purposes? The short answer is maybe — it depends on the tradeoffs.
For example, it is known that when hemp (and drug-type I or II tetrahydrocannabinol-rich cannabis) is grown to produce cannabinoids, fertilization should be avoided. Cannabinoids are produced in the trichomes (from the Greek for ‘hairs’) which are most abundant on the female flowers, but also present on other tissues such as leaves. As we discussed in another post, Cannabis has males, females, and monoecious (hermaphrodite) individuals that can interbreed. Cannabis grown for cannabinoids should not be fertilized for two reasons. First, once fertilized, the plant starts allocating resources to seeds instead of cannabinoid production. Second, no one wants seeds in their joints, which, according to non-scientific evidence, explode with heat!
So, here we see a clear trade off: either seeds or cannabinoids. Therefore, if we want a variety that produces seeds, we should not aim to also produce cannabinoids. (Unless… we can produce cannabinoids in the trichomes of the leaves instead of flowers which would also avoid some legal loopholes. But this crazy idea is subject for another post.)
But what if we are growing hemp for both seed and fiber? Or for cannabinoids (flower) and fiber? Can that be possible? Again, the answer is maybe. These options do not seem to pose much of a tradeoff threat.
In the first scenario, the flower would produce seeds and the stalk would be used for fiber. Under this scenario, to assure seed production, we would probably want a monoecious variety that can self-fertilize (or fertilize its neighbors), or we want a dioecious variety that produces a reliable number of males that would fertilize the females. This would mean that selection on the crop should be made on those individuals that produce the best fiber, which appears to vary between varieties [2] and sex [3], and on those females or hermaphrodites that produce the best looking, biggest, and most oily seeds.
In the second scenario where we cultivate hemp for fiber and cannabinoids, we would want a variety that produces the best fiber, but only females that produce big trichome-laden buds. However, this second scenario may come with a trade-off since drug-type plants grown for flowers usually have a lot of branches with multiple buds, and are thus grown with sufficient space between them. On the contrary, hemp grown for fiber usually has a long stalk without many branches allowing densely planted fields with multiple plants grown in a small space.
Many of these traits can be independently selected for (or against) [4], are not correlated to one another (can be broken by recombination), and may allow the development of hemp for multiple purposes. Some research suggests that growers and breeders should have clear goals for their crop [5], but so far, at least in the US, there is little investigation on the possibility of multi-purpose hemp varieties. These researchers also suggest that monoecious varieties are the way to go, and they found that growing hemp for seed and for fiber may be a possibility.
I want to leave you with other understudied possibilities that deserve more research. Hemp is an environmentally friendly crop that can help with bioremediation [6], and can be used to suppress weeds (ironically weed suppresses weeds), and for crop rotation. These other uses for hemp may or may not pose trade-offs regarding fiber, seed, or cannabinoid production. Hemp that was used for bioremediation, such as in oil spills and particularly for nuclear waste, should not be used for clothing or for medical consumption. I wouldn’t want to wear some cool Adidas radioactive shoes. However, I wouldn’t mind some seed on my granola from weed-killing hemp. Would you?
Dr. Daniela Vergara is a member of the Cornell Cooperative Extension, the founder and director of the non-profit organization Agricultural Genomics Foundation that aims on bringing Cannabis science to a general public through the podcast ‘Cannabis Science Today’ (@cannabis_science_today), through courses offered at the University of Colorado Boulder, and through blogposts. Your donations help us keep this Cannabis education ongoing and are tax-exempt. Follow Dr. Vergara on twitter @Cannagenomics
References
[1] Schluttenhofer C, Yuan L. Challenges towards revitalizing hemp: A multifaceted crop. Trends Plant Sci. 2017;22(11):917-929. [journal impact factor = 18.313; times cited = 114][2] Musio S, Müssig J, Amaducci S. Optimizing hemp fiber production for high performance composite applications. Front Plant Sci. 2018;9:1702. [journal impact factor = 5.753; times cited = 27]
[3] Salentijn EMJ, Petit J, Trindade LM. The complex interactions between flowering behavior and fiber quality in hemp. Front Plant Sci. 2019;10:614. [journal impact factor = 5.753; times cited = 30]
[4] Vergara D, Feathers C, Huscher EL, Holmes B, Haas JA, Kane NC. Widely assumed phenotypic associations in Cannabis sativa lack a shared genetic basis. PeerJ. 2021;9:e10672. [journal impact factor = 2.984; times cited = 3]
[5] Baldini M, Ferfuia C, Piani B, Sepulcri A, Dorigo G, Zuliani F, Danuso F, Cattivello C. The performance and potentiality of monoecious hemp (Cannabis sativa L.) cultivars as a multipurpose crop. Agronomy. 2018; 8(9):162. [journal impact factor = 2.24; times cited = 25]
[6] Adesina I, Bhowmik A, Sharma H, Shahbazi A. A review on the current state of knowledge of growing conditions, agronomic soil health practices and utilities of hemp in the United States. Agriculture. 2020; 10(4):129. [journal impact factor = 2.925; times cited = 42]
