How to Harvest and Dry Hemp for CBD Production
There is a lot of interest in growing industrial hemp for CBD production, especially since hemp was legalized in the 2018 Farm Bill. Take a look at some of my previous articles regarding the potential risks and rewards in the CBD market as well as agronomic considerations for successful industrial hemp production.
Fresh cut hemp drying. Whole plants hung in this fashion during the drying phase may have humidity trapped in the center due to the ‘closed umbrella’ shape that an entire plant takes on. Breaking off and hanging individual branches is recommended. Photo by George Place.
CBD oil extraction process. Photo by George Place
Harvesting hemp is a critical stage for CBD production. The presence of molds and mildews will lower the value of hemp floral biomass so a timely harvest is essential. There are visual clues on the hemp bud that growers should monitor. When trichomes on the hemp bud shift from white to milky white it may be time to harvest.
Weekly testing of CBD content can inform the grower of when harvest should be initiated. This is in addition to the required THC test with the North Carolina Department of Agriculture. While some of the tests for CBD, cannabinoids, terpenes, pesticide residue, mold, and heavy metals can cost as much as $300 the return on investment can be significant. For example, if 1000 lbs of biomass will be harvested on one acre the difference between harvesting when the crop is at 6% CBD versus when the crop is at 7%CBD is equivalent to 10 pounds of CBD oil. Current prices for CBD oil are $5 per gram. With 454 grams per pound, a 1% discrepancy in CBD content on one acre can be a $20,000 crop value difference. Growers need to test frequently to make the right decision regarding harvest timing.
Weather will also be a key factor in determining when to pull the harvest trigger. Harvest time for hemp coincides with the hurricane season. Growers will have an easier time drying and curing their hemp floral biomass if they can bring it in before the arrival of a storm. This is the time when adequate labor is crucial. The vast majority of hemp growers for the CBD market are relying on labor to cut the stalk (the machete is the current tool of choice) and load the biomass. This takes a lot of time and physical exertion. I have heard reports of growers that had an excellent crop of hemp floral biomass but suffered massive losses because they could not harvest it in time (their two-person harvest team was not adequate). The importance of measuring the labor requirement is a big reason why we recommend that first-year hemp growers for the CBD market start with 1 acre or less. Growers need to keep track of the amount of man and woman hours that it takes to bring in the harvest. Maintaining sharp tools during the harvest process will also save time and effort.
Drying and Curing Hemp
Hemp biomass made from chipping the entire hemp plant. This biomass is low quality and will receive a reduced price. Photo by George Place
Once hemp is harvested growers should immediately move the floral biomass to the drying facility. This could be a simple structure like a barn. The facility should be under roof, out of direct sunlight, and well ventilated. Growers need to set up several fans and have them blowing continuously. Significant ventilation is crucial! Ideal temperatures for drying and curing are 60 to 70 degrees F at 60% humidity. Some processors say that hemp growers should not dry their floral biomass at the same temperatures as flu-cured tobacco. Those temps are too high and dry the hemp too quickly. A slow drying with high airflow will cure the hemp, produce a higher quality end product (better cannabinoid and terpene spectrum), and fetch a higher price.
It is difficult to estimate the square footage of drying space needed per plant. Using a flu-cured tobacco with 800 square feet a grower was able to dry 1 acre worth of plants (approximately 1350 plants) in 3 days. Another grower was able to dry approximately 1.5 acres worth of hemp (plant number not stated) in a 2500 square foot barn.
Hanging entire plants upside down on wires in the drying barn is a common practice. Unfortunately, as those plants dry the branches droop down in the formation of a closing umbrella. That closing umbrella shape results in less airflow to the center of that entire hemp plant. Thus more mold and mildew will grow in that center portion. We advise growers to break off the individual branches from the hemp plant and hang branches on the drying wire, not whole plants. This step is more labor intensive but will help minimize mold and mildew.
Dry and shucked (stem removed) hemp flower biomass. Photo by George Place
Dry hemp biomass still on the stem, referred to as unshucked. Photo by George PlaceThere is a lot of interest in growing industrial hemp for CBD production, especially since hemp was legalized in the 2018 Farm Bill. Take a look at some of my previous articles regarding the potential risks and rewards in the CBD market as well as agronomic considerations for successful industrial hemp production. Hemp Production – Keeping …
Because the hemp industry is relatively new and still growing in North America, many producers still lack suitable equipment, infrastructure, systems, and know-how to deliver a quality hemp product.
Industrial hemp processing, be it for fiber, seeds, or CBD, is currently going through a renaissance. Growers are rediscovering a century-old technology as well as innovating new products, processes, and equipment for the present day. Whether it’s for industrial use or CBD extraction, the basic post-harvest handling is relatively similar.
That said, there are many differences when it comes to CBD-rich hemp, as opposed to hemp cultivated for industrial purposes. Processing equipment and practices will vary depending on the type of hemp grown, cultivation, and standard processes used in the region. Because the industry is still young, different farms and regions will adopt unique approaches.
The Importance of Hemp Drying
The importance of hemp drying post-harvest cannot be understated. There are plenty of things that go into the cultivation and harvesting process of hemp, but the drying process can make or break the quality of the product.
If hemp is dried cleanly, properly, and promptly, there will be minimal damage or loss. As such, this will maximize the quality of fiber, food, or medicinal products resulting from the harvest. On the other hand, if the hemp is dried improperly (too wet, too slowly, with inadequate or insufficient ventilation) or becomes contaminated with bacteria, fungi, etc., your harvest may be completely unsuitable for food or medicinal processing.
Farmers who want to enter the hemp industry will often fail to address this important aspect of the post-harvest process, putting them in a difficult situation. That said, there are a couple of ways to dry hemp.
Outdoor Hemp Drying
When dealing with hemp intended for seed or fiber use, it’s not uncommon to dry hemp outdoors in drier climates. This process can work well on warm, dry days, but it can result in significant damage to the product if rain, fog, or other intemperate weather patterns that slow the drying process or allow for mold to set in. Farmers looking to dry their product outside should also minimize the accumulation of dust, weeds, or other elements that may contaminate the drying crop.
Indoor Hemp Drying
More commonly, however, hemp is dried indoors. For optimal conditions, farmers should use environmentally-controlled rooms or specialized warehouses. To the untrained eye, improperly dried hemp is susceptible to mold and humidity, incorrect temperature and ultraviolet light. Therefore, dehumidifiers, large fans, heaters, AC units, are all used to improve the balance between humidity and temperature (ideally 61%, 61 degrees respectively), and overall airflow during the drying process.
Nevertheless, it is important that these facilities offer a suitable standard, mainly if you’re dealing with food or medicinal products. For example, these facilities will need to have clean and dry floors and ensure that there are no insect or animal infestations that could contaminate the product. Farmers with barns that previously housed animals such as horses need to be cautious as they can also introduce potential contaminants.
When it comes to hemp used for its CBD, properly drying the plants will ensure maximum preservation of CBD value and terpene content. It’s also best that each stem is separated, rather than drying the whole plant. These can be hung from a trellis, chains, or other structures to maximize space.
There are also types of hemp industrial ‘flash’ drying machines which can dry large volumes at a faster pace. However, some will use excessive heat, which can degrade cannabinoids and vaporize terpenes found in hemp. Ideally, these machines should use warm, dry air and movement for the drying process.Hemp drying Because the hemp industry is relatively new and still growing in North America, many producers still lack suitable equipment, infrastructure, systems, and know-how to deliver a ]]>