Photos courtesy of Marguerite Bolt
A moldy grain seed head

Hemp producers face considerable challenges during the growing season. But the challenges don’t stop once the hemp is harvested. The process of drying and storing harvested material requires considerable planning and is a part of production that growers sometimes overlook. One of the key mistakes hemp growers make is waiting until the plants are already in the ground to try to figure out how to dry and store their harvested crops. Some growers overlook the quality of their hemp. The quality of material being harvested plays a huge role in successful drying and storage.

Here are some of the large mistakes growers make in drying and storage, and three methods to prevent them in the future.

1. Make a plan before planting.

One of the biggest mistakes I see is a lack of pre-plant planning. Growing a hemp crop is so much more than just having a production method and getting plants in the ground. There needs to be a strategy from production specifics all the way to selling the crop. One of the biggest areas growers overlook is how to dry their crops. This is going to vary greatly across fiber, grain and cannabinoid production. In last month’s Hemp Grower article, “Preserving Your Harvest,” drying methods are described for each type of production. Regardless of production method, a space to dry and store hemp is crucial. It’s not usually feasible to put up a structure for drying or storing the crop during the growing season. Managing a crop while figuring out how to dry it is a stressor that growers can easily avoid.

Growers ideally should determine their production plans from seed to storage before they even apply for a hemp license. Look at existing infrastructure on site and alternatives like mechanical drying or facilities that may have space to dry and store hemp crops. If growers don’t have storage space, identify a company that can store the material to preserve and insure it. If the crop is going to be immediately sold after drying, long-term storage is not a concern, but space for short-term storage may still be needed.

Insurance on storage buildings and the contents of those buildings is another way to protect against peril events. Some hemp-focused insurers offer options for buildings, equipment, and hemp material post-harvest. While these services would come at a price, it may be unrealistic to put up a space on the farm in the first year or two of production. There are more and more companies providing equipment or services to mechanically dry hemp plants and even provide storage. Growers who want to go this route should reach out to their state or regional hemp associations and talk with other growers and consultants to get insight on companies they are interested in working with. They should also read policies and agreements thoroughly.

Growers may hang dry hemp in metal pole barns like this (or any structure) if there is good ventilation to reduce humidity. Hanging large plants may increase molding on the inner portions, and branches may need to be removed and hung separately.

2. Don’t put poor quality in to avoid poor quality out.

A great drying and storage plan will not mean much if the quality of material being harvested is poor. Some factors that cause a decrease in quality may be unavoidable, like a disease outbreak. However, knowing the potential pests, developing pest management strategies, and regularly inspecting plants throughout the growing season can reduce the risk of damage.

Excessive insect damage, mold and other pathogen contamination as well as weed contamination decrease the quality of hemp and may result in a loss of crop material during storage. This has been a problem for some growers when late-season pests are feeding on the flower and grain, including corn earworm and Eurasian hemp borer. The damage from these pests can lead to infection and dieback. Even without insect damage, some producers still struggle with a multitude of pathogens, causing necrotic tissue. Seeds from weeds in grain hemp production can reduce profitability if not cleaned. Stems of weeds baled in with hemp stalks can also decrease the value.

There are several approaches to reduce the likelihood of poor-quality hemp making it into storage. While active in-season management is critical for the health of the plant, it also decreases the chance of suffering excessive pest damage. Some growers have faced cataclysmic outbreaks and have very few tools to deal with those issues once they are already taking place. There is not much that can be done at the point of serious outbreak, so scouting early and often may enable growers to catch issues before they become more severe. Oftentimes damage may be isolated to a few hemp flowers on large plants or only exist on the edge of a field.

Clipping away damaged plant material is one way to reduce the chance of poor-quality hemp getting dried and stored. Sanitizing tools and cutting back disease material will reduce the movement of inoculum to healthy tissue. Bag and dispose of the material that is removed to reduce inoculum in the field.

This becomes more challenging with mechanical harvesting of grain or cannabinoid hemp. Equipment can move inoculum, contaminating clean material and potentially moving it to other fields if multiple harvests occur. While it may be difficult or impossible to avoid widespread infection when mechanically harvesting, cleaning equipment in between harvests is important to reduce the movement of inoculum. Develop protocols to clean and disinfect different pieces of equipment. The equipment manufacturers should have recommendations to do this and how to avoid damaging electrical components.

If damage is isolated to margins or pockets of a field, it may be possible to avoid those areas. In the worst-case scenario, excessive damage or heavy weed pressure may mean forfeiting the crop and foregoing harvest. While this is a terrible situation, spending the time, money and space to harvest, dry and store a contaminated crop is more of a loss.

A moldy grain seed head. Pathogen contamination can decrease quality.
Photos courtesy of Marguerite Bolt

3. Store it right.

Growers often have to store hemp for both short and long periods of time. One mistake is choosing a space that has temperature and humidity fluctuations or light exposure. This is made even worse when hemp with a high moisture content is improperly dried and then stored. It is an awful sight to come back to hemp that has turned moldy from condensation inside the storage container or to find out that light exposure has degraded the quality of hemp when it comes time to sell. This is not just an issue among cannabinoid producers. Grain producers can face the same issues when it comes to concerns about molds, other microbiological contaminants and loss of quality due to storing in a space not suited for hemp.

Choose a site that is going to keep harvested hemp at a stable moisture level and won’t expose the material to light. This may seem straightforward, but a space that seems suitable during the winter months while planning for the upcoming season could be unsuitable during the fall if there is not humidity or temperature control.

Growers may also want to test grain or cannabinoid flower for microbiological contaminates after drying and before storage, and then again when the crop is about to be sold. Some buyers may provide this service; it is important to make sure the material is safe and meets standards set by the buyer and government (if available). A microbiology laboratory can screen for a whole panel of tests, including E. coli, salmonella, yeasts, molds, and total microbials. As the industry develops, so will safety standards.

Regardless of the type of hemp being produced, the method of drying, the storage space and having a plan well in advance can prevent headaches down the road.

Marguerite Bolt is the hemp extension specialist at Purdue University’s Department of Agronomy. She received her M.S. in entomology from Purdue University and her B.S. in entomology from Michigan State University. Bolt’s research has focused on hemp-insect interactions and plant chemistry.