Hemp Production for CBD – Revised
University of Nebraska-Lincoln Extension information typically is based on the interpretation of research information from Nebraska or elsewhere in the Midwest. However, such information is not available for hemp production due to previous restrictions on research in the U.S. This publication relies heavily on research findings from Europe and Canada and learning from growers’ experiences. See more stories in this series at https://cropwatch.unl.edu/tags/hemp.
Demand for CBD, a non-psychoactive compound derived from hemp, has soared for un-validated treatment of many conditions and illnesses. However, an approximate 75% plummet in prices for the CBD feedstock during 2019 indicates that the supply exceeded demand.
CBD-containing products marketed in the US range from cosmetics to chocolate bars to bottled water to pet treats, all with no regulation. The Food and Drug Administration warned marketers of CBD products against the use of non-validated health claims to sell their products. In June 2019 the FDA approved the first CBD-based drug, called Epidiolex, to treat seizures caused by extreme types of epilepsy. The efficacy of CBD for treatment of chronic pain, neuro-inflammation, anxiety, addiction, and anti-psychotic effects has not been well-validated by clinical research.
Hemp grown for CBD is a high-value crop grown more as a horticultural than as an agronomic crop. It has a high labor demand, putting US production at a disadvantage with production in China and other countries with relatively inexpensive labor.
Hemp CBD varieties have not been well-validated for Nebraska but possibilities may include ‘Abocus’, ‘Autopilot’, ‘Boax’, Cherry Wine, Cherry Blossom, Cobbler, and Sweetgrass for high pharmaceutical-grade CBD yield but having less than 0.3% THC.. High CBD varieties are generally grown only as female plants, as the combination of male and female plants leads to seed production and decreased CBD yield. Breeders continue to improve the processes for creating stable feminized seed. Farmers need to be wary of the source of their feminized seed stock and to check test results for validation of feminized seed.
Farmers need to know state regulations for testing hemp for CBD and THC. The Nebraska Department of Agriculture (NDA) regulations for industrial hemp production have been approved by USDA. Plant sampling by NDA staff to test for THC needs to be within 15 days before the date of harvest with the grower present during sampling. If the THC level is >0.3% by dry weight, the crop will not meet the legal definition of industrial hemp and need to be destroyed. Again, THC is expected to increase with stressful growing conditions.
CBD varieties have short plants with much branching, growing as squat bushes. The suggested spacing at this time is 2-4 feet x 6 feet. Planting practices may change for higher plant densities when seed supply is sufficient to greatly reduce the cost of seed. Given the high cost of seed, seedlings should be produced in a greenhouse for transplanting. If planting more than five acres, machine transplanting is recommended which may allow transplanting 2 acres per day. Plants can also be produced from cuttings with similar vigor and productivity compared to plants from seedlings. Propagation from cuttings may improve plant uniformity and is a means to all-female plants. The potting mix for greenhouse production of seedlings is important but needs to be well-drained with good available water holding capacity and nutrient supply. The mix probably should include sandy loam soil, perlite, and some organic material.
The CBD levels can be much reduced by cross-pollination with wild or non-CBD hemp. The CBD plants must be well-separated by distance or time of pollination from hemp weeds or another hemp crop. Also, a few rows of corn or forage sorghum can planted around the plots to reduce pollen flow.
The highest concentration of CBD is in the bracts of female flowers but CBD oil may be extracted from the whole plant. Harvest may be by topping plants for the harvest of mostly leaves and flowers, by picking the leaves and flowers from the plant, or by taking most of the plant cut at 8-12” above the ground. The whole plant harvest may be by shredding such as with a silage chopper or by keeping the plant intact.
Drying the plant material is a major operation as the water content is high when harvested. To reduce the quantity to be dried and handled for CBD production, the woody stems may be removed for land application, composting or dried separately for fiber production. Artificial drying at up to 100 o F should be continuous flow but the temperature of the plant material should not exceed 75 o F. Suspending plants or branches upside down by wires indoors out of the sun and with good air movement for air drying at up to 75 o F is a common practice if the harvest is not too large.
The ground-up plant material is soaked in grain alcohol or ethanol to extract the CBD oil. After soaking, the mix is pressed to extract the liquid. The alcohol is then evaporated off leaving the CBD oil.
Drying for smoke able buds is an option. Smoking of CBD is reported to be more effective than oral consumption. The buds are preferred but some upper leaves may be included. Well-dried material can be kept and sold in sealable plastic bags or glass jars.
Market information is too weak for prediction or advice but information is improving such as with a USDA ERS Feb 2020 report.
For information on budgeting for hemp grain, fiber and CBD production, see worksheets from Pennsylvania State University and from the University of Kentucky.
How to Harvest and Dry Hemp for CBD Production
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Estoy de Acuerdo / I agree
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 Place
How To Harvest Hemp
The success of your hemp CBD or CBG crop will depend on the efficiency of your harvest processes. Harvesting a commercial hemp crop is a carefully choreographed process where scheduling, labor, equipment, and facilities must be accounted for. As the hemp industry continues to mature, hemp farmers and equipment manufacturers have been working together to develop effective harvest techniques.
Today, hemp harvest practices borrow from both commercial agriculture and cannabis cultivation. To illustrate, farmers who grow hemp for bulk biomass get many of their harvest methods from industrial farming. Conversely, hemp producers who grow boutique flowers follow many of the careful harvest parameters of craft cannabis production. In this article, we’ll look specifically at how to harvest both hemp biomass and hemp flowers.
The harvesting process can be broken up into three broad phases:
- Choosing the right harvest time
- Harvesting your hemp
- Drying and curing your hemp
Part 1: Choosing the Right Time to Harvest Your Hemp
As a rule of thumb, full-term hemp requires 100 to 120 days to mature. Nonetheless, different geographies present both opportunities and challenges when it comes to timing a hemp harvest. In colder climates, you will want to choose hemp strains that finish by late September.
Choosing the right time to harvest your hemp will impact your ROI. If you harvest too early, your plants may not reach their full resin potential. Harvest too late, and your flowers could lose their potency. (Yes, CBD and CBG potency drops quickly after hemp plants reach maturity.) Even more, harvesting late in certain regions of the country like Colorado will put your crop at risk with early season frost and snow.
To hammer home how important good timing is, consider that harvesting 1,000 pounds of hemp biomass with 7% CBD instead of 8% CBD will mean a loss of approximately 10 pounds of CBD oil. With CBD oil selling at roughly $5 per gram, losing just 1% of CBD potency will result in a loss of $20,000 per 1,000 pounds of biomass.
As if finding this balance wasn’t difficult enough, farmers must also keep in mind that THC rates rise quickly as hemp plants reach maturation. According to the 2018 Farm Bill, hemp farmers must keep their hemp crop below a 0.3% THC threshold. If you wait too long to harvest and your crop’s THC potency rises above 0.3%, you’ll have to throw away your entire crop.
How to Decide When to Harvest
In most regions of North America, hemp crops are ready for harvest between mid-August and early October. Farmers with a small hemp crop used to be able to use visual cues to determine the ideal time to harvest their crop. Looking closely, farmers could spot a plant’s trichomes (small, mushroom-like glands on hemp flowers). When the trichomes turn from clear to a milky white color, the plants are ready for harvest. Nowadays, even small farmers need to test to stay in compliance with regulations so going on visual clues is not recommended for beginners.
Industrial hemp farmers are better off determining the right harvest time by regularly testing their plants with a laboratory. While testing hemp crops might be expensive, it offers a great way to get exact readings on cannabinoid levels in your plants. By taking the guesswork out of harvesting, you will ensure your hemp crop remains compliant according to state and federal guidelines. As some states require testing before harvest, you might have to undertake this step at your hemp farm anyway.
Weather May Dictate Your Harvest
Farmers also need to keep an eye on the sky when choosing the right time to harvest their hemp crop. Farmers in the north of the country or at high altitudes must watch for an early cold snap. Hemp is a robust plant, but it can’t survive a hard frost. Additionally, harvest season also coincides with hurricane season, so farmers on the East Coast and Gulf Coast need to track hurricanes and tropical storms.
Rain can cause serious issues for hemp growers. Not only will excessive rain during harvest season contribute to broken branches on plants, but excessive moisture can help propagate mold. Large flowers are particularly susceptible to botrytis or “bud rot” in wet conditions.
Part 2: How to Harvest Hemp at Your Farm
Your harvest processes will be dictated by the type of CBD or CBG hemp you are growing. If you are growing hemp for CBD or CBG biomass, you can use industrial hemp farming equipment to harvest your crop. However, if you are growing hemp for smokable flowers, you will have to cut down plants individually by hand.
How to Harvest Hemp Flowers by Hand
Harvesting hemp by hand protects the integrity of the flower. As CBD and CBG flowers are sold as smokable products, you must ensure that trichomes, terpenes, and pistils are not damaged during the harvest process. Mishandling these delicate flowers can greatly reduce their value on the open market.
Harvesting hemp by hand is labor-intensive. Workers typically use machetes, shears, or tobacco knives to cut the stalks and bring the hemp to a waiting wagon or trailer. Where to cut the hemp depends on how the farmer intends to dry it. If you plan on screen-drying your hemp, you’ll want to cut smaller sections, so it is easier to lay them on the screens. If you are going to hang dry, you can afford to cut larger sections of the hemp.
How to Harvest Hemp Biomass with Machines
Hemp biomass requires different harvest processes than hemp flowers. As hemp biomass is grown on an industrial scale for CBD and CBG extracts, it doesn’t require as much care as hemp flowers. As such, farmers use industrial agriculture equipment like combines to harvest hemp biomass. By using combines, you can harvest acres of hemp in quick order.
Understanding Your Labor Needs
One of the most common mistakes new farmers make is underestimating the labor requirements of the hemp harvesting process. Farmers who don’t bring on enough labor could face dire financial consequences if their harvest falls behind schedule and their mature hemp plants run hot.
Farmers need to hire enough workers to efficiently harvest their hemp. They also need to build the harvesting time into their overall hemp schedule to make sure their plants don’t over-mature while the laborers work. It’s a good idea for workers to start harvesting hemp with the largest and densest flowers. Workers may also want to start by cutting top flowers first, leaving lower flowers to mature a little more before a second pass. The ACS Laboratory suggests that 15 experienced workers can harvest five to six acres of hemp per day.
New Farmers Should Start Small
We strongly recommend that farmers plant only a few acres of hemp for their first season, or even just a single acre. Planting a small amount of acreage will help farmers understand how much labor they need per acre of hemp, so they can scale up appropriately when they plant more next year. Also, planting a single acre of hemp lets farmers experiment with growing techniques and helps them understand how hemp performs on their farm before making a large investment in the crop.
Part 3: Drying Your Hemp
Some farmers send their hemp biomass directly to a processor after harvesting, but many choose to dry and cure the hemp on their property before this step. Again, your choice for drying and curing hemp will largely be dictated by whether you are growing flowers or biomass. Drying the hemp helps lock in the hemp’s quality and potency. If a hemp plant isn’t cured properly, it could grow mold or lower the quality (and overall market value) of the product.
Drying is another part of the hemp harvesting process where farmers use different methods and are actively experimenting to improve their outcomes. All farmers will agree that drying requires a drying facility. This should be a roofed structure with good ventilation. Many farmers use a barn, shed, or warehouse to serve as their drying facility.
Ventilation Is Key
One of the most important factors in the drying and curing process is good ventilation. To achieve proper airflow, you should use wall fans, inline fans, and industrial blowers.
How to Dry Hemp
When it comes to drying hemp, methods vary. Some farmers use racks or screens. A common method is to hang hemp plants upside down from wires. If you plan to use this method, we recommend that you break off the branches of your hemp plants and hang them individually.
When Is Your Hemp Dry?
How dry does hemp need to be before a farmer can send it off to the processor? Typically, farmers will want to get below 15% moisture (below 12% is even better.)
Curing Your Hemp
Some processors will expect farmers to go beyond drying their hemp and cure the hemp as well, which means taking out even more moisture. Curing adds a lot of time to the drying process, but it also locks in the smell and taste the flowers.
During the drying and curing process, farmers will also want to test hemp plants one more time. The final test will let farmers know the CBD or CBG content of their crop and ensure the crop is under the THC limit. The test can also show any contamination that could affect the quality of the crop.
The last step in the curing and drying process will depend on what the processor asks for. Some farmers send their dried hemp directly to the processors while others shuck the hemp and remove the stalk. Still, others will trim the hemp, cutting away the leaves and sending only the flowers. Trimming can be performed by hand or, for larger operations, with the help of a mechanical trimmer.
Have More Questions on How to Harvest Hemp?
Here at High Grade Hemp Seed, we get the question “how do you harvest hemp?” all the time. The answer really depends on your goals, budget, and personal preferences. If you still want to know how to harvest CBD strains or harvest industrial hemp, contact our representatives today and we would be glad to lend you our expertise.