How and When to Harvest Hemp
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FAQs in this post –
Unsuitable harvesting can render countless acres of viable hemp useless. That’s why it’s so vital to consider your final product and the quality you hope to achieve before choosing the appropriate harvesting method. And with thousands of uses for hemp, the answer is not always so obvious. Moreover, the harvest method you choose must produce a legally compliant crop that tests below .3% THC, and is safe to ingest. In order to be sure of that, you must meticulously time your harvest and test samples of the crop throughout the lifecycle.
At ACS Laboratory, we offer testing solutions for every step of the hemp cultivation process and have compiled a list of frequently asked harvesting questions to help set you up for success. With your product, compliance and product safety in mind, let’s dive into the details of how and when to harvest your hemp.
When is hemp harvest season?
Unlike perennial plants that come and go each year, hemp is an annual plant . That means under most circumstances it grows from a seed to a plant in 90-120 days and its buds blossom once before dying off for the next crops to be planted. Hemp is affected by seasonal changes so once the days start to shorten, the crop stops growing tall and begins producing flower buds instead. That’s why the busy season for hemp harvesting in most states is October , also known as Croptober .
However, if you’re growing indoors, technically you can create Croptober all year ‘round by altering temperatures, lighting, moisture and other required conditions. Additionally in warmer climates with proper greenhouse support you may be able to achieve 2 turns a year. This would include 6-8 weeks in the greenhouse and 8-10 weeks in the field for full bloom. The key is to test your product throughout its lifecycle and create an ideal growth environment based on your location and capabilities. Then inspect your plants to ensure that they’ve matured to an optimal stage before you begin harvest.
Can hemp crops be harvested by hand?
Yes. While this process is time consuming and may be costly, sometimes hand harvesting is the optimal choice. If you’re growing hemp for smokable flower or CBD extraction, you may opt to cut the plants by hand to ensure that you carefully collect and maintain the integrity of each bud. Additionally, if you have a small farm or lack access to machinery, you may also want to harvest by hand. In this case you may use tobacco knives or shearers to cut the plants before loading them on to trailers and carefully transporting them to a facility for drying and curing.
But harvesting by hand is also time-consuming and labor-intensive, so if you’re a first-time hemp cultivator, start small with an acre or less. Then, keep track of the time and manpower it takes to harvest your hemp plants so you can plan accordingly. For example, if you do not have enough manpower to harvest your crops before they are over-mature, you may accidentally produce a plant with THC higher than .3%. At that point, you must destroy your entire harvest and risk losing the time and money you invested.
Can hemp be harvested with a combine?
Yes – If you are harvesting hemp for its seeds (grain), you may utilize a combine . For this purpose, combine harvesting is highly efficient due to its ability to cut a swath about 40 feet wide through a field. Combines are optimal when harvesting hemp seeds on a wide scale, but they can easily shatter seeds at moisture levels lower than 15%. Combines can also increase levels of microbial contamination if hail or rain flattens the swath of plants into the ground. So you must assess your field for swathing potential and carefully adjust your settings for optimal combine harvesting. According to the Canandian Hemp Trade Alliance (CHTA), you will need to experiment with ground speed, concave openings, and air speed.
CHTA suggests the following as a starting point:
- Cylinder Speed – 450 – 600 rpm
- Concave – 30 – 50 mm
- Wind – 1070 rpm
- Sieve – 3mm
- Chaffer – 10mm
How do I harvest smokable hemp flower?
Hemp flowers are very delicate and easy to bruise, which is why most farmers harvest smokable hemp flowers by hand. Harvesting by hand will ensure your hemp flower heads remain clean and their resin trichomes remain intact. Unharmed and mature resin trichomes are vital for smokable hemp flower because they contain most of the full spectrum of cannabinoids (CBD and THC) and terpenes that produce the plant’s flavor, fragrance and therapeutic effects.
For the most efficient hand harvest, you may want to identify the sections where the flowers are the biggest and densest–and start there. Then you’ll cut roughly a foot and a half to two-foot sections of the plants going mostly for the top flowers. In order to conduct this process efficiently, you will need to ensure that you have the right amount of labor based on the number of acres of land you have. For reference, the director of operations and farmer for Swan Lake farms in Oregon, Landon Butterfield said 15 people were able to hand harvest 5 to 6 acres of flowers per day.
When do I harvest hemp for smokable flower?
If harvesting hemp for smokable flower, you probably want it to contain high levels of CBD. You may also want it to contain a delicate balance of terpenes to provide the aroma and flavor you desire. This will provide a high-quality product that customers expect from smokable hemp. But several factors such as environmental conditions and nutrient levels can prevent the plant from reaching the cannabinoid profile you desire. That’s why it’s important to test early, at the vegetative phase to ensure your final plant meets the requirements.
After the vegetative phase, you’ll want to harvest the plant when it is abundant with mature flower heads. If looking through a microscope, the trichomes –tiny hairs growing on the plant–should be a milky white instead of translucent. This indicates that it contains a high concentration of cannabinoids. After harvest, you must ensure that the plant is properly ventilated, without direct sunlight and in a comfortable climate between 60-70° F to prevent contamination and preserve its genetic profile. At this point you’ll want to test your flower to confirm its potency of CBD, THC and terpenes. You’ll also want to guarantee that your harvest is free of toxins such as mildew, bacteria, and pesticides to name a few. At ACS Laboratory, we offer comprehensive flower potency and safety testing to guarantee the quality and compliance of your smokable hemp flower.
How do I harvest hemp for industrial fiber?
Hemp stalks are known for their incredible yield of fibre which can be used for everything from textiles, clothes, and paper. If you’re growing hemp for fibre from its stalks, you’ll want to plant them in close proximity for maximum yield and select seeds that grow tall. Once they are ready for harvest, the process is much less precise and easier than harvesting hemp for its seeds or flowers.
All that you need is specialized equipment for cutting hemp for fibre. According to CHTA, you can use a discbine, a disc mower, or a straight sickle mower for best results. One major advantage of the discbine in particular is that it can cut at speeds of 9mph, much higher than average machinery. If you are harvesting hemp for textiles however, you may want to use a straight sickle mower which leaves stems in tact and neatly organized directly on the ground. All hemp should be harvested approximately 10 cm above the ground to prevent cutting through hard woody portion and ensure that your cutting has much of the fibrous stems as possible. Once harvested, you’ll want to facilitate drying to reduce the potential for mold.
When do I harvest hemp for industrial fiber?
If you’re growing hemp for its stalks and fibre content, you do not need to consider precise levels of cannabinoids or terpenes when determining when to harvest. However you must still ensure that your plant has grown to its optimal height, contains less than .3% THC and is contaminant-free. That means you must carefully choose your seeds based on its strain genetics and test early in the pre-harvest phase to ensure that the crop is clean and contains the amount of THC you expect.
If you’re growing hemp for fibre, you’ll want to harvest the plant when you’ve achieved the maximum volume and quality of stalks. This point is reached prior to seed set and the dying off of the male plants, which can occur between 90-100 days. Generally, you’ll want to harvest your hemp when its flowers first emerge and then store them in a way that prevents over moisturization, which causes mold. Before processing your hemp you’ll want to double check it is below the THC limit and that it is free of any toxins that may compromise the finished product. At ACS we test industrial hemp plants for THC potency and a broad spectrum of possible contaminants.
How do I harvest hemp planned for CBD extraction?
Just like smokeable flower (link to section above) , hemp for CBD extraction is harvested for its flower heads, which contain the bulk of cannabinoids that are later extracted into CBD oils, waxes and creams. That means you’ll likely want to hand harvest your crop utilizing the amount of labor and tools you need to efficiently conduct this precise process.
When to harvest hemp for maximum cannabinoids?
Similar to the process of harvesting hemp for smokeable flower (link to section above) , you’ll want to harvest hemp for CBD extraction when its buds mature to optimal potency. You’ll also want to be on the lookout for mildews and molds, which could compromise the hemp’s floral biomass. As with smokable flower, you may want to test your hemp-for-CBD-extraction early and often for potency to ensure its reaching the level you seek. You also need to test for THC to ensure your crop stays below the legal limit. In addition to potency testing, you’ll want to test for contaminants such as metals, mold, and bacteria throughout the crop’s entire lifecycle.
How do I harvest hemp for seeds?
Hemp seeds, which gather around the heads of the plant are great sources of oils and grains that can be used in food, cosmetics and supplements. If you’re growing hemp for seed production you’ll want to select strains that are shorter in stature with lower fibre production. Then once you’re ready to harvest you may want to use combines to efficiently cut swaths of the plant and prepare for post harvest production. According to the CHTA, Canadian producers have identified the following techniques for best combine practices:
- Use draper heads because they leave more room for hemp heads
- Experiment with ground speed, concave openings, sieves, wind speed. See best starting settings above (link to section above).
- Monitor grain tank and adjust concave to minimize cracking of grain
- Combine at 15 to 18% moisture.
- See full list here
When do I harvest seeds from hemp plants?
If you’re harvesting hemp for seeds, cannabinoid and terpene potency don’t really matter except for the 0.3% THC limit. Because of the potential to lose your entire crop if it tests above the legal limit, it’s important to test pre-harvest, during vegetation and after harvest to ensure that it remains compliant.
For optimal harvest, you’ll want to assess female plants at the stage that provides optimum seed yield with minimal immature seeds. When visually inspecting, make sure that the seed heads (buds) are still mostly green. You may notice a few leaves on the seed head turning a brownish color. The stem fibres will have shed most of their leaves, but will not be completely matured. When the seeds at the base of the stem and leaf stalk at the bottom of the seed head begin to turn gray, you’ll know it’s time to harvest. Once your crop is harvested, you’ll want to submit samples for testing to guarantee that is free of mold, mildew, pesticides, and other harmful contaminants.
Understanding how and when to harvest your hemp, along with the tests you need to ensure the product matches your customers’ (and the government’s) expectations is no simple feat. But the opportunities to create a thriving brand and lucrative product are limitless. Through education, trial and error, and testing, you’ll be ready to harvest your hemp for successful commercial sale. Contact the team at ACS Laboratory to learn more about our accredited hemp testing services.
ACS Laboratory in Tampa, FL – How and When to Harvest Hemp . We're an ISO17025 Certified laboratory dedicated to servicing the cannabis and hemp industries from cultivation through to MMTCs and recreational dispensaries.
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 Place
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. Hemp Production – Keeping …