The information in this post was compiled in an attempt to understand 2 issues:
- Does the cultivation of hemp differ depending on the hemp product supplied (fiber, seed, or flower)?
- Is the CBD produced from hemp (cannabis with ≤ 0.3% THC) identical to the CBD produced from marijuana (cannabis with > 0.3% THC)?
Hemp for Fiber vs. Seed vs. CBD
The hemp plant has the potential to contribute resources into the production of a profusion of different end products. These end products are generally sourced from one of three parts of the plant: stalk, seeds, or flower (see Figure 1).
Currently, some hemp suppliers cultivate single-use (stalk or seed or CBD) hemp, while others grow dual-use (stalk and seed or seed and CBD) hemp. At the same time, marijuana cultivators also supply the market with CBD (see Figure 2).
To clarify, hemp seed is used to produce hempseed oil, where hempseed oil does not contain any CBD. CBD comes primarily from flower and is generally supplied either in oil or powder form. But again, hempseed oil comes from the seed and contains no CBD, whereas CBD oil comes (primarily) from the flower (resin).
A hemp plant cannot simultaneously produce high-yield/quality stalk and high-yield/quality seed and high-yield/quality flower. Rather, generating high-yield/quality of one part of the plant comes only by sacrificing yield/quality of the other parts. This is due to three factors: genetics, limits on plant resources, and differences in cultivation techniques.
The first factor preventing simultaneous optimization of hemp stalk, seed, and flower yield/quality is plant genetics. Plant genetics shape such plant characteristics as sex, height, fiber quality, flowering time, seed size, resin potential, and CBD:THC potential.
The second factor preventing simultaneous optimization of hemp stalk, seed, and flower yields involves plant resources. In particular, the hemp plant only has a fixed amount of resources to allocate across its various activities (see Figure 3).
To enhance the yield/quality of one part of the plant – either stalk or seed or flower – the plant must devote fewer resources to, thereby degrading the yield/quality of, the other parts of the plant.
The last factor preventing simultaneous optimization of stalk, seed, and flower is the fact that cultivation techniques vary depending on the part being optimized. Specifically, to grow high-yield/quality stalk, suppliers must cross-breed and cultivate plants to focus more resources on the stalk. The best stalk (fiber) crops are male plants that are packed densely together; they grow tall, with long, thick stalks and few leaves (see Figure 4). Male plants die soon after they flower. So fiber plants (which are male) are harvested relatively early, just as they’re flowering.
In contrast, high-yield/quality seed crops require cross-breeding and cultivating plants that focus more resources on seed. Suppliers give these plants more room than fiber crops for roots and leaves to grow, generating shorter plants with more leaves (see Figure 4). Hiqh-yield/quality seed plants are females whose flowers are pollinated to generate ample seed crops. Once flowers have been pollinated, however, plants stop producing resin and focus instead on nurturing their seeds. Seed crops are harvested later than crops for stalks (fiber), after most seeds have matured.
Finally, growing hiqh-yield/quality flower involves cross-breeding and cultivating female plants to generate resin that’s rich in CBD but low in THC. Genetics favoring seed production differ from genetics favoring CBD (resin) production. Furthermore, resin plants are given even more room for flowers to grow, generating shorter, bushier plants than seed crops (see Figure 4). Also, in contrast to seed hemp, plants used to grow flower (resin/CBD) are prevented from being pollinated. By preventing pollination cultivators induce plants to continue producing resin (in further attempts to attract pollinators). Flowers are harvested when the resin matures.
Source: Ernest Small and David Marcus (2002). Hemp: A New Crop with New Uses for North America https://www.hort.purdue.edu/newcrop/ncnu02/v5-284.html
To fully optimize the yield or quality of a particular hemp product, cultivators must simultaneously focus genetics and plant resources and growing methods on optimizing one part of the plant. Growers do cultivate dual-use crops (for example in China and Russia), but the yields from those crops do not provide the highest yield/quality of either of the two outputs (fiber and grain or grain and CBD). In short, optimization of output is a zero-sum game: producers can only generate the highest yield/quality of a particular output by sacrificing yield/quality of the other parts.
Ultimately, I think higher yield/quality crops will be more cost-effective than dual-use crops. That is, I think competition will force most suppliers to focus on single-use supply. In this case, there will eventually be separate grow and sales markets for hemp stalk, seed, and flower (see Figure 5).
CBD from Marijuana Is Healthier Than Hemp/CBD
There are two separate grow markets – hemp and marijuana – that are supplying CBD product markets. While the two sets of growers both supply the same consumer market for CBD, hemp and marijuana crops have historically existed within vastly different cultivation regimes. At the same time, regulations in supply markets differ radically between the two sources. These two factors, differences in both cultivation methods and regulations, have created differences in plant characteristics - and thus the nature of CBD yields - from hemp/CBD and marijuana/CBD.
CBD isolate from hemp may be identical to isolate from marijuana. However, a less pure form, say a 10% concentration, will not be the same across the two sources: the residual 90% portion of the hemp solution will contain different compounds than those in the residual portion of the marijuana solution, and those differences may very well affect the end-user experience. In particular, “the best source of CBD oil is organically grown, high-resin, CBD-rich cannabis not low-resin industrial hemp.” There are three factors in particular that make marijuana/CBD healthier than hemp/CBD: testing, chemical diversity, and potential contaminants.
Products in marijuana markets must be tested to assess levels of purity and to assure lack of contaminants. However, products in the hemp market are not required to undergo testing, other than to assure concentrations of THC are below 0.3%. Consumers are thus not assured of the safety or potency of hemp/CBD products.
Hemp/CBD is “less chemically diverse” than marijuana/CBD:
Industrial hemp is less chemically diverse than high resin cannabis, lacking the robust mix of medicinal terpenes and secondary cannabinoids commonly found in high resin cannabis.
If you were to come across a 100-acre field of industrial hemp you might notice a whiff of cannabis aroma, but because these plants are low in beneficial terpenes, the scent is not very strong. On the other hand, a 100-acre field of PCR [phytocannabinoid rich] hemp would stink to high heaven like really strong marijuana.
In addition to being more chemically diverse, the trichomes in marijuana have high resin content, while those in hemp do not.
Industrial hemp flower clusters (let’s just call them buds), generally appear only at the very top of the plant and are generally small. And those buds are not only nearly devoid of THC, but are also severely lacking in the CBD department. PCR [phytocannabinoid rich] hemp buds, on the other hand, produce somewhere in the neighborhood of 15% to 20% cannabinoids. They are also rich in beneficial terpenes. It is from these buds that high-quality, broad spectrum CBD oil is produced.
Because marijuana is resin-rich, it takes much less biomass to generate, say, a pound of CBD oil than it takes to generate the same pound of oil from a resin-poor hemp plant. “This raises the risk of contaminants as hemp is a 'bio-accumulator'— meaning the plant naturally draws toxins from the soil.” At the same time, much hemp/CBD oil is generated as a byproduct from hemp that is primarily grown for fiber or seed. In this case, the quantity of biomass needed to generate that same pound of CBD oil is much greater, thereby increasing the potential for the final extract to contain residual contaminants.
Finally, “Compared to high-resin cannabis, low-resin hemp is more vulnerable to pest and mold infestation because the resin contains terpenes as well as cannabinoids that repel predators, attract beneficial insects, and protect plants from blight.”
 Charles Wortmann (2019, Jul 30). Hemp Production for Fiber or Grain. Cropwatch. Retrieved from https://cropwatch.unl.edu/2019/hemp-production-fiber-or-grain
 CBD Hemp Is Not the Hemp You’ve Heard About. Joy Organics. Retrieved from https://joyorganics.com/cbd-hemp-is-not-the-hemp-youve-heard-about/
 Mojave Richmond & Robert C. Clarke (2019, Sep 18). The Challenges of Seeded vs. Seedless Cannabis. Cannabis Business Times. Retrieved from https://www.cannabisbusinesstimes.com/article/seeded-seedless-cannabis-hemp-fiber-seed-oil-cbd-needs/
 Hemp Project. Purdue University. Retrieved from https://purduehemp.org/hemp-production/
 Melissa Moore (2018, May 3). The Difference Between Hemp and Cannabis as a Medicine. Labroots. Retrieved from https://www.labroots.com/trending/cannabis-sciences/8701/diferrence-hemp-medicine-cannabis-medicine
 Martin Lee. Cannabis Oil vs. Hemp Oil. Project CBD. Retrieved from https://www.projectcbd.org/cbd-101/cannabis-oil-vs-hemp-oil