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Hemp – History, Cultivation and How to Dry Hemp

Hemp refers to strains of cannabis sativa with very low levels of THC. Usually under 0.3%, too low for commercial recreational use. Regardless of the lack of THC, many consider it a super-crop, with an especially wide range of uses.

Hemp, or cannabis, is undergoing a cultural shift, especially with a comeback from illegality in the U.S. This is a great time to understand the history, functions and cultural practices of hemp.

A Brief History of Cannabis

Cannabis is a plant with a rich history. From archaeological findings in Japan, dating back as far as 8,000 BC to second century findings in the Middle East. During the 17th century, the Spanish transported the plant around the world. This led to industrial cultivation of the crop in North America, Europe and Asia, as recently as the early 1900’s.

Hemp is making a comeback. This is part of a reawakening of the cannabis industry, including legalization of the plant in many countries. Hemp’s return is most evident in the 2018 U.S. Farm Bill, officially legalizing the THC-free crop on a federal level.

Hemp in the modern age may fulfill a wide array of functions. Classically, it’s cultivated for its fiber, from which fabric, ropes and paper can be made. Modern uses of hemp fiber reach much further, including biodegradable plastics, bio fuels, construction materials and more.

But not all uses are related to its fiber. Much of hemp’s modern appeal is actually its seeds. Cannabis seeds are a rich source of protein and other nutrients, making their oil valuable for industrial and culinary purposes. Hemp seeds are also as relatively cheap, high potency livestock feed. Legalization will also further the study and application of cannabidiol (CBD) extracts, used in most medicinal cannabis products.

Breaking it down, there are three main purposes for hemp cultivation: fiber, seed or CBD. Each of these comes with its own cultivation practices and optimal traits.

Cultivating Hemp

Hemp is a great crop for organic farmers, growing fast and tall with minimal inputs. It even outcompetes most weeds. In comparison, it grows larger than corn, but requires less water and nutrients. Hemp is also praised for being relatively resistant to pests and diseases, meaning less pesticides are necessary to grow it. Growers consider it a sturdy plant, being able to grow in most non-extreme climates.

Cannabis thrives in warmer temperatures. It is often planted in the spring, growing over the summer for three to four months. After harvesting, hemp requires drying for several days. Drying is a very important part of cultivation and varies greatly, depending on the designated function of the end product.

For the best results, hemp should be grown in nutrient rich soil and controllable water flow. Though it can survive in temperatures as low as -5oC, and seeds may germinate in as low as 1oC, warmer temperatures of between 18-26oC are preferable. Hemp’s water consumption is around 300-500 liters per kg of dry plant, a fraction of most commodity crops. Furthermore, hemp is a great rotation crop. It aids in suppressing weeds, loosening the soil and improving its tilth. It is also compatible to grow as a monoculture, though some pests, bacteria and fungi will eventually accumulate, leading to a decline in crop health.

Drying Hemp

A major concern in hemp cultivation is the need to dry after harvesting. Though all hemp cultivation purposes share this concern, the specifics and importance differ.

Drying Buds for CBD

Cultivation for CBD, either as raw bud or for extraction purposes, requires a mold free product. In order to minimize the outbreak of molds, such as botrytis, downy mildew or powdery mildew, the post-harvest plant should be transported immediately to a drying room. From here on out, the drying process is no different from that of cannabis cultivated for recreational or medical use containing THC.

Optimal cannabis drying conditions are:

These conditions help avoid any water appearance in the space, providing optimal drying. This includes the inside of the bud, where humidity may easily build up, due to the dense nature of the cannabis flower. The plant is still alive after harvesting, and therefore continues to transpire. Maintaining the correct conditions reduces the loss of product and ensures the highest quality.

Drying Hemp Seed

Producing seeds doesn’t require the actual flower, but has its own set of requirements and limitations. In order to minimize loss to birds or seed shattering, growers combine hemp while still green, with a high water content. The harvested hemp requires aeration and drying within the first few hours, as the moisture during harvest is too high for safe storage. Heating is a common method of drying hemp for fiber. But heating hemp seeds causes them to oxidize, develop molds, and may even scorch the seeds. These reduce the quality and quantity of oil production. Therefore, alternative drying systems are required, such as refrigeration-based dehumidification.

Seeds have very strict storage requirements. In order to safely store, the moisture content must be under 9%. Some seed processors require exactly 8%, meaning there is little to no wiggle room. Seeds that undergo heating are usually rejected for food use. The same is true for moldy seeds, reducing their value.

The best drying practices combine the correct temperatures for the intended purpose, good aeration and efficient water removal, while keeping inputs to a minimum.