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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.

FAQs

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.

Hemp Biomass: A Step-by-Step Guide to Harvesting

What is Hemp Biomass?

Hemp Biomass is the remaining organic material (stalks & leaves) after the flowers and/or seeds have been harvested from the plant.

Biomass can be regarded as “waste” in conventional farming, but this is not the case with hemp. There are two methods for collecting hemp biomass, and each are dependent on your end goals.

For collection of oils, leaves, or for use as fuel, hemp biomass should be dried as effectively as possible before further processing.

For fibre, cloth, or cord production hemp biomass should be “retted.” This insures the fibrous strands that make up the stalk can further separate to make further processing more efficient.

Hemp leaves and stalks can be used to produce a wide variety of goods. Having a successful hemp harvest is key to the quality of theses goods. There are a few factors that are imperative to know, to get the most from your crop.

What We’ll Need to Harvest Hemp Biomass:

For CBD Biomass: Flower, Oils, Leaves or Fuel

  • Machete, scythe, or shears
  • Transportation Vehicle
  • Drying location
  • Storage location
  • Processing equipment (Oil press, container, etc.)

For Hemp Fibre Biomass

  • Machete, scythe or shears
  • Transportation Vehicle
  • Retting Location
  • Storage Location
  • Decorticator (fiber extraction machine)

The Hemp Biomass Harvest

Depending on your geographical location, this stage needs to be planned well before you sow your first seeds in the ground.

In North America, hemp harvest typically takes place in late-summer/early-fall. Natural weather patterns lead to hurricanes on the Atlantic and prime wildfire season on the Pacific. Timing is very important.

The size of your crop is directly related to the size of your harving team or equipment. If the crop is too large for the team of harvesters to cut and transport during the time of harvest, not only is man power wasted, but the risk of loss in the quality of your crop due to mold, mildew, and bacteria increases drastically.

Crop size = Harvesting style

The size of your crop should be based on the method of which you plan to harvest.

1-2 people

(by hand)

Size: 1 acre or less

I recommend starting with one acre or less for the first season. This allows you the freedom to test a manageable harvest and drying period. Starting slowly will also help you to understand the needs for harvesting hemp biomass. You will soon understand if you have the proper facilities for production.

4-6 people

(by hand)

Size: 2-4 acres

A hemp harvest of 2 acres is a perfectly balanced size. This could be done with as little as 2-4 people, but also allows for proper crop rotation through the year. One acre can grow the production crop while the other is rejuvenated. I recommend rejuvenating soil with a cover crop such as legumes, buckwheat, or alfalfa.

Combine Applications

5+ acres

Combines are very expensive to own and maintain, yet they cut harvesting time down to almost nothing. The mantantice cost, mechanical settings, and operation experience necessary for optimum harvest are a few factors to consider.

For larger applications, the additional expense may be worth the investment. Time is money, and harvesting hemp is no exception.

Once you have experience growing hemp at 2-4 acres, the combine is most effective way of growing your yield. Unless you are willing to hire a team of skilled, manual harvesters, a Combine is the only way to sucessfully harvest hemp in a short window of time.

If hemp is going to be cut with a combine then the correct conditions for cutting need to be assessed before hand.
The proper conditions to harvest hemp with a combine are:

  • humidity (50% or less)
  • temperatures (65-90°F)
  • wind (light wind)

[BONUS TIP] Be sure to check the following days forecast and ensure there is no precipitation. This will allow the hemp to dry out properly before being baled.

Harvesting hemp plants should be on days where there is no precipitation in the forecast. Ensure there is adequate time to move the harvest into storage for the next stage of processing prior to any precipitation.

When harvesting, plants should be cut 2-3cm from the soil with a machete, scythe, or shears and stacked in piles for easy transport. Once the field is cut, there are two options for the next stage: Drying or Retting.

Drying Hemp Biomass

Drying hemp can be done in a variety of ways. From the inside of a sterile lab facility, to the rafters of an open air barn, the major factor here is space and adequate air flow.

The quickest way to reduce the quality of your crop is retaining moisture. While moisture is your friend during the growing period, as soon as the stalk is cut down rid as much moisture from the stalk as possible. Otherwise, mold and mildew can grow rapidly and reduce the quality of your harvest. This will effect the quality of your finished product as well.

Some choose to hang the entire plant upside down like traditional tobacco. However, this can allow for moisture build-up near the center of the plant. Hanging can also lead to mold and mildew growth making the plant less than desirable for production.

Snipping each branch from the plant and hanging them individually, allows for not only a quicker drying process and results in less product loss.

Hanging can be done a variety of ways. Hemp is commonly hung by wedging the stalk/branch through traditional drying wires or clamps. These wires/clamps allow it to hang with adequate air flow (from a fan or breeze) to dry for 3-5 days.

The times the plant need to dry are solely based on temperature, plant size, and air flow. Some plants may take a little longer than others.

Retting Hemp Biomass

If you intend on using your hemp biomass for fibre, retting can help make the process more effective. Retting uses micro-organisms and moisture to break down the stalk separating the individual fibres from the remainder of the stalk. This can be done two ways.

Water Retting

This is the most common type of retting and is done by soaking the stalks in water. Soaking them in water causes the cellular membrane to swell, and allows for easy separation of the fibre. There are two methods for using water retting

  • Natural Water Retting
    • A tried and true method, done for centuries around the globe. Natural water retting involves submerging hemp stalks in a naturally occurring water source such as a stream, river, or pond. When using a natural water source, be sure to secure the bundles of stalks under the water with a weight assuring that they do not float back to the surface. This process normally takes 8-14 days depending on the mineral content of the water.
  • Tank Retting
    • As the name suggests this method is done in controlled conditions, such as inside a container for 4-8 days. The process is faster and allows for another valuable post-harvest product, mineral dense water. This water can be poured back onto the field as liquid fertilizer, as long as no harsh chemicals were used on the crop during growth. If harsh chemicals were used then the water needs to be filtered before returning it to the soil.

With either form of water retting, the biomass then needs to be dried for a few days (1-3) to begin a curing process that will allow for easier processing in the next stage.

Dew Retting

Dew retting is only appropriate for climates where water is sparse. After the hemp is cut, it is then laid flat on the ground, in rows allowing air flow around each stalk. The night will bring in moisture and then the day will bring warmth and light, promoting bacterial growth.

This creates a moisture rich microclimate within each stalk that allows for a similar breakdown in the biomass creating equal separation. Though, it does take a while longer (2-4 weeks) and the quality of “dew retting” biomass has been know to be lower than “water retting.”

Hemp Biomass Storage

There are a number of ways to store hemp biomass and each depend on harvesting methods and end goals.

With manual harvest methods dried hemp can be stored in everything from plastic garbage bags, plastic bins, or cotton/hemp sacks. Stored then in a covered low moisture barn or similar low moisture storage facility.

For the combine farmer, once the hemp is cut it will be also need to dry out for a few days. To promote faster drying, try raking with a hay rake or tedder to arrange into biomass into rows.

Once it is dry the hemp will be baled by an automatic baler and tractor. Hemp can be baled with any hay baler.
It can be baled using square or round bales based on the storage option for each unique situation. The biggest focus here is to do everything to insure low moisture content in each bale, 15% or less.

It is essential to reduce the moisture content. Not only for the prevention of rot and bacteria, but for another frightening reality. Bales can spontaneously combust due to the close proximity of the biological material and bacteria feeding within the bale.

This is not hard to test and there are warning signs that are “tells” that the bales may be getting too warm. The most visible, is steam emission.

If the ceiling or eaves of the barn/storage facility are showing signs of condensation, action will need to be taken. Call the fire department immediately. Bales should be tested and checked regularly with a probing thermometer.

Another simple way to test the internal temperature of the bales is to insert a iron rod as far into and as close to the center of the bale as possible. Remove the rod after two hours and feel the temperature of the metal.

If it is too hot to handle easily, then the temperatures have increased above 120°F and action should be taken. Although bale storage does require additional maintenance, it is manageable if hemp is cut under the right conditions and the moisture content is monitored throughout the process.

Hemp Biomass Processing

One of the most rewarding parts of the process is taking what you have grown for months and seeing the final product. With so many finished goods possibilities, each it unique in its own way.

Fibre

Processing fibre can be done by hand with protective gloves and a club or baton.

Most processing of fibre is done using a “decorticator.” A decorticator is a machine used to strip the bark/skin off the hemp stalks.

They range from manual hand-crank to automatic fully-electric. When selecting a decorticator, confirm that it has settings to process hemp.

The dried biomass is run through the machine’s ridgid crank system breaking the hard outer shell/skin from the stalk and separating the fibres. Creating a workable product for production use.

From here the dried biomass is ready to be stored until enough of the biomass has been harvested to allow for viable oil production. Decorticator can be also used to “shuck” the dried biomass, making oil production more organized and efficient.

The dried leaves can now be removed from the stalk and stored for later tea use. The leaves can remain loose or tea filter bags can be purchased for individual servings.

Fuels

Now the biomass is dry it is able to burn burned for fuel in fire places, cast iron stoves, or thermoelectric generators.

Hemp Biomass is the remaining material after the flowers and/or seeds have been harvested from the plant. There are two methods to harvest hemp biomass.