How to Grow Hemp for CBD
Growing hemp for CBD
The federal legalization of hemp via the 2018 Farm Bill was a pivotal moment in cannabis history—it was, however, underrated by the cannabis community at large. This mainly has to do with the fact that cannabis with less than 0.3 percent THC will not get you high but also a mistaken belief that "hemp" is not considered cannabis. Hemp is cannabis, and cannabis with less than 0.3 percent delta-9 THC is now legal in the U.S.
Perhaps the biggest revelation is that some U.S. farmers, who may have never considered growing cannabis, will now start learning to become cannabis farmers. Growing cannabis outdoors for high concentration of Cannabidiolic acid (CBDa) is similar to growing cannabis outdoors for high concentration of tetrahydrocannabinolic acid (THCa). With that said, cannabis cultivated for CBD-rich flower or biomass is generally more difficult to plant, upkeep, and harvest than cannabis varieties traditionally grown for grain and fiber. For this reason, this planting guide focuses on hemp produced for Cannabidiol (CBD). We hope this guide will be helpful to beginning farmers looking to grow hemp for CBD purposes.
View the PDF version of the Hemp CBD Planting Guide.
Cannabis producers will need to decide on varieties based on the desired end product: fiber, grain, grain/fiber, or cannabinoids. Every cannabis variety will have its own unique set of characteristics: short or tall, small or large seed, higher or lower cannabinoid content, different flowering times, and different nutrient requirements.
This includes cannabis varieties bred to exhibit high concentration of CBDa. Only female hemp plants will produce flowers with high contents of cannabinoids.
Grain varieties are bred to produce high yields of seeds that are food grade quality. Both male and female plants are needed to produce a grain crop.
Planted in high density, this cannabis variety is bred as a bast fiber crop. Fiber varieties are typically taller, and fibers are removed from the stalks after retting or softening of the fiber.
Cannabis can also be bred as monoecious (hermaphrodite) for dual purpose use. Dual purpose varieties are bred to produce both grain and fiber.
The optimal temperature for cannabis seed germination is 65-70°F. Lower temperatures will delay emergence. It’s best to plant after potential risk of late frost (e.g., mid-May or early June). Seed is best planted at a depth of 0.75-1 inch. For direct seeding, acceptable soil temperature at that depth for germination is 50°F.
Cannabis grows best on loose, well-drained, well-aerated soil with a pH of 6.0-7.0. Consistency in pH level will allow the plant to better absorb nutrients. If pH becomes too alkaline (above 7.5) or too acidic (below 5.5), it will cause deficiencies of nutrients. Cannabis does not do well in heavy clay soils due to higher calcium levels and greater water retention/saturation.
Cannabis generally prefers semi-humid conditions with temperatures between 60- 80°F. Cannabis does not react well to over watering but requires ample moisture during early stages. Excess rainfall will stunt growth and lead to smaller yields. During the plant’s life-cycle 10-14 inches of rainfall is optimal, but larger plants will require more water. Irrigation may be necessary depending on size and geographic location.
Cannabis germinates best in a firm bed but is sensitive to soil compaction and soil crusting. Good soil moisture is necessary for seed germination. Cracked or dull-looking cannabis seeds are not likely to germinate.
Soaking: One method to encourage germination is to soften the seeds by soaking them in distilled water overnight (8-12 hours) at 65-70° F. After soaking, transfer seeds to a small 4”x4” pot or seedling tray. This method assumes transplanting after 2-3 weeks versus direct seeding outside.
Cannabis has different nutritional needs based on the stage of its life cycle. Nitrogen is recommended during vegetative stage (e.g., NPK ratio of 3:1:2), while phosphorus and potassium are recommended for the flowering stage (e.g., NPK ratio of 1:3:4 then tapering off to 0:3:4).
Cannabis is an annual plant belonging to the small family of flowering plants called Cannabaceae. The lifespan of cannabis grown outdoors is about 120 days: 30-60 days for vegetative growth and approximately 60 days for flowering time, varying by genetics.
Although cannabis will grow well in Midwest soil, it’s important to note that cannabis is not a native plant to the region or to the United States; it is indigenous to central Asia and the East Indies. Cannabis has been cultivated mainly for fiber production in China, Russia, Italy, Czech Republic, Slovenia, Poland, Netherlands, Hungary, Germany, France, Japan, Canada, and more.
While Cannabis sativa is an important source of durable fibers, nutritious seeds, and medical extracts, the plant is poorly understood genetically. Unfortunately, due to past U.S. prohibition of the cannabis plant almost no U.S.-based agronomic research existed until 2015.
With that said, the planting calendar and nutrient recommendations below are for educational purposes only. Further fertility research will need to be completed to determine best practices.
Nitrogen and potassium uptake are greatest during the first two months of growth. Higher rates of potassium and phosphorus are needed during the flowering stage. Sources of micronutrients include dead plant tissues, compost, and manure. The breakdown of organic matter (i.e. roots and leaves) will add nutrients back into the soil. No-till and holistic soil building practices are encouraged for creating fertile soil.
Male vs. Female
Contrary to popular belief, hemp plants are NOT male “marijuana” plants. Only female hemp plants will produce flowers rich in CBDa. Cannabis pistils, which are often referred to as "hairs" of the cannabis bud, can help identify female plants early on. Female cannabis plants will continue to flower, forming fragrant buds until they are pollinated or harvested.
Cannabis grown for grain and stalks produces very little cannabinoid content— close to 0% THCa and 0% CBDa. However, the government classifies “hemp” as any cannabis plant containing less than 0.3% delta-9 THC. Therefore, breeders have been able to develop high-CBD, low-THC cannabis plants while falling under the legal classification, and social construct, of hemp.
The hemp plants, from which most CBD is extracted, is not your typical industrial cannabis grown for fiber or grain; genetically, they are different. Genes of the cannabis plant fight to convert the precursor cannabinoid CBGa to either THCa or CBDa, and plants can be bred to exhibit dominance in either cannabinoid.
Know the difference.
Male (Grain & Fiber)
Fiber and grain varieties will be grown from regular seeds, resulting in both male and female plants. While both male and female structures are needed to produce grain, a higher ratio of female plants is desirable to maximize the yield per acre. Only female plants live to mature seed stage.
There is no apparent difference in the fiber from male or female plants, but male plants will mature faster than female plants. Producers looking to grow cannabinoid-rich flowers should beware of males from neighboring grain or fiber crop. Pollen can potentially travel miles, seeding female plants close by.
Female (Grain, Fiber, & CBD)
Un-pollinated female flowers will produce higher concentrations of cannabinoids and terpenes than pollinated flowers. When starting from regular seeds, male and female plants will occur almost equally but generally a higher ratio of females is desired. To limit the likelihood of producing male plants, CBD-rich varieties may be feminized, meaning the seeds were produced by female plants intentionally pollenated by another female (monoecious) plant.
Feminized seeds are generally more expensive, but they will result in little to no males in a field. Sinsemilla is an unnatural state for cannabis so plants should be monitored closely.
Hermaphrodite (Grain & Fiber)
While cannabis plants are dioecious, having separate sexes, it’s possible for female plants to grow pollen sacs which may then pollinate its own flower. Inducing female plants to grow male sex organs is a common breeding technique to produce feminized seeds.
Monoecious or hermaphrodite plants may be desirable for seed production or dual purpose use. Dual purpose varieties are bred to produce both grain and fiber.
Transplanting & Cloning
If you are anticipating a longer flowering period on a particular variety but have limited time due to seasonal changes, starting from clones can be a good way to get ahead, skipping the germination and seedling phase. Growing from clones can also be a way to catch up if you are starting later in the season (i.e. late June or early July). Cloning can save time but also can ensure that your crop will be genetically identical to the mother plant.
When starting from clones, there will be transplanting involved. Transplanting is also a popular method when starting seedlings indoors earlier in the season when outdoor temperatures are not yet suitable for planting (below 60°F).
Starting from clones can be advantageous when growing CBD-rich varieties. Cloning essentially takes the guess work out of sexing plants and improves the odds of a hemp plant not “going hot”, or exhibiting a concentration of delta-9 THC higher than 0.3 percent.
The difference between hemp and recreational or medical cannabis is distinguishable by two separate genes which are tightly linked and fight to convert the precursor cannabinoid, CBGa, to either THCa or CBDa— the acidic forms of THC and CBD. Consequently, higher levels of CBDa imply higher levels of THCa.
When THC production genes are turned “on” and CBD is turned “off,” plants are THC dominant, psychoactive, and are considered recreational and medical. When both CBD and THC genes are turned “on,” plants are moderately psychoactive (as CBD potentially lessens the psychoactivity of THC) and are considered medical. When CBD production genes are turned “on” and THC is “off,” plants are considered industrial or food product.
Whether cannabis varieties bred to produce high concentration of CBDa and low concentration of THCa will be more or less likely to go “hot” in more fertile soil is yet to be studied. Therefore, clones of mother plants grown in local conditions or perhaps well-adapted to the local environment pose the least risk.
Outdoor (CBD Biomass)
Opportunities for outdoor cultivation can substantially lower startup costs, but harvesting CBD-rich cannabis is laborsome. Small hemp farms may need extra farmhands to harvest the crop in time. Proper spacing supports efficient harvesting.
Rows are typically 4’ x 4’ or up to 6-8 feet between rows depending on the variety. Cannabis cultivated outdoors for CBD purposes will mainly be processed into biomass to produce CBD extracts.
Preemptive measures should be taken to reduce the risk of contamination, e.g., pesticide blow over, heavy metal contamination, or microbial contamination.
Outdoor (Grain & Fiber)
Grain and fiber varieties are typically planted in 6-7 inch rows, resulting in about 400,000-600,000 grain plants per acre and 800,000-1,000,000 fiber plants per acre. Fiber varieties should be planted more densely to prevent branching while grain varieties will need more space to produce flowers.
Fiber and grain varieties will both start from regular seeds. Grain varieties will need about 25 pounds of seed per acre (approx. 25,000-27,000 seeds per pound), accounting for 70-80 percent germination rate. Fiber varieties will need up to 100 pounds per acre.
Indoor/Sungrown (CBD Flower)
Indoor cultivation facilities offer more control over the growing environment but can be more capital-intensive when using artificial lighting. However, indoor cultivation also includes sun-grown cannabis in greenhouses or enclosed hoop houses, allowing for the use of light deprivation.
Hemp CBD 101
While many industrial farms are preparing to grow hemp at large scale, there are many advantages to small-scale production. First, failing small is better than failing big. Cannabis cultivated for CBD-rich flower or biomass is generally more difficult to plant, upkeep, and harvest. Growing at large scale while maintaining high-quality will be challenging.
Uses for CBD -Rich Flower
- Herb: While most recreational and medical cannabis cultivators focus on high-THC, low-CBD chemovars (strains), hemp can be grown to reach high levels of CBD and low levels of THC. Hemp is a great option for those seeking to benefit from the cannabis plant's potential medicinal and therapeutic properties without getting high.
- Crude Oil: Crude oil refers to extract that closely resembles the cannabinoid/terpene profile of the original plant. CBD concentration tends to be between 40-50%. Crude oil is extracted via ethanol or supercritical CO2.
- Distillate: Distillate with a higher concentration of cannabinoid content is produced using fractional distillation. Most terpenes and minor cannabinoids are lost in the refinement process.
- Isolate: 98-100% pure CBD. CBD must be isolated from decarboxylated, full spectrum plant material to create THC-free CBD products. CBD isolate is flavorless.
Levels of pesticides that we are used to seeing in food, which are considered tolerable, are not likely to be attractive or even acceptable to processors and consumers of hemp CBD products. Soil testing before planting is a great idea.
Depending on the type of extract and level of refinement, you may see low levels of pesticides become concentrated at higher levels no longer suitable for human consumption without proper remediation. Remediation adds more cost to processing. For this reason, cannabis grown in organic soil using holistic management practices will be in higher demand.
Consider the following before planting:
- Test soil fertility ($30)
- Test soil for pesticide residue ($300)
- Test soil for heavy metals ($60)
- Avoid rotations with corn and soybeans
- Reduce water saturation with proper runoff
- Remove weak or diseased plants
- Use sterile, clean equipment
- Manage pests before flowering
Some cannabis producers will focus on producing as much biomass as possible without necessarily thinking about the environmental impact of pesticide, insecticide, and herbicide use. Most industrial farmers are used to spraying crops to prevent pests and disease. However, by using methods such as companion planting, mulching, composting, and Integrated Pest Management, producers of cannabis can help improve biodiversity and soil biology.
Organic standards prohibit the use of most synthetic substances—including most pesticides used in conventional agriculture—for at least three years prior to the harvest of an organic crop. Even so, USDA organic regulations allow residues of prohibited pesticides up to 5 percent of the EPA tolerance.
Pesticides, insecticides, and herbicides used in conventional farming practices will deter beneficial insects and microbes that would otherwise aid in pest and disease control. Integrated Pest Management (IPM) practices in conjunction with holistic methods that allow beneficial microbes to thrive are recommended when producing cannabis for human consumption.
IPM is an environmentally sensitive approach to pest management using proactive methods that support healthy soil.
Integrated Pest Management
- Ladybugs: Ladybugs are a popular, beneficial insect that mainly prey on aphids and mites. A single ladybug can eat up to 50 aphids per day or 5,000 in its lifespan. It's important to use the right species of ladybugs. Harmonia axyridis, or the Asian lady beetle, and Coccinella septempunctata, sevenspotted lady beetle, are commonly used for aphid control. Consider planting flowers that ladybugs are attracted to: yarrow, marigold, dill, fennel, and dandelion to name a few.
- Praying Mantis: Similar to ladybugs, the praying mantis is attracted to fragrant, colorful plants. However, praying mantises will eat both pests and beneficial insects. Other beneficial insects may include predatory mites, wasps, and beetles. Consider planting flowers and culinary herbs like holy basil, thyme, oregano, yarrow, chamomile, calendula, clover, dandelion, aster, nettle, fennel, and marigolds as a cover crop.
- Green Lacewing: Green lacewings work well as a general predator. Consider planting dill, coriander, fennel, and dandelion to attract lacewings.
- Predatory Mites: Predatory mites target two-spotted spider mites, broad mites, russet mites, cyclamen mites, and other mite species.
Humidity, water saturation, lack of airflow, and excess foliage are likely to cause fungal diseases and microbial contamination. Gray mold and powdery mildew are the most common diseases caused by humid conditions and excess moisture. Cannabis infected by mold, powdery mildew, and other fungi pose a potential threat to cannabis consumers. Mold should not be confused with the plant's trichomes or the resinous glands that produce cannabinoids and terpenes.
Preventative measures include planting in areas with proper drainage and runoff (i.e. mounded rows), providing ample spacing for plants to grow and to improve air circulation, and proactively pruning plants to remove excess foliage. After harvesting, proper drying and storage of cannabis flowers to control humidity levels is extremely important.
Excess water may also cause root rot. In the Midwest, plasticulture is likely not necessary. With heavy rainfalls, raised beds with plastic ground cover are bound to cause over saturation and lead to beds drying too slowly.
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