Samuel des Bordes and Heather Kirk-Ballard

Since the passing of legislation in Louisiana in 2019, farmers have been able to grow hemp once again. With only three years of growing since the passing of this legislation, growers have faced challenges and look to the future for promising opportunities in the production of this specialty crop. Producers and researchers have used a variety of growing practices and faced several challenges. LSU AgCenter researchers are making recommendations for future growing practices for Louisiana hemp farmers for the following commonly used systems.

Indoor Production

Indoor production offers farmers the highest level of environmental control. When growing indoors, cultivators can optimize the growing environment by adjusting temperature, humidity, carbon dioxide (CO2) and lighting, and cultivators can better control for plant diseases like Botrytis, stem canker and southern blight. Indoor production also allows for complete photocontrol. Growers can control light intensity, light duration and light quality. Manipulation of light quality and intensity is also possible by using various light sources. They may also manipulate the distance the plant is from the light source to increase or decrease light intensity. Light duration can be adjusted to increase or decrease day length and to autonomously regulate photoperiods. However, this increased environmental control comes at a significant cost, as indoor production is by far the most expensive production system used in growing Cannabis sativa, the species that includes hemp and marijuana.

Greenhouse Production

Greenhouse production allows for partial photocontrol, which means to control light levels. Due to the photosensitive nature of Cannabis sativa, special consideration must be given to selecting both cultivars and planting dates when full photocontrol cannot be achieved. Growers can decrease light intensity by using translucent greenhouse materials that allow for a percentage of light to pass through greenhouse ceilings and walls. Growers may also provide supplemental lighting to increase light intensity, light duration or implement night breaking. However, in this system day length may not be shortened unless fully opaque shade cloths are installed both on the ceilings and walls of the structure. If greenhouses are properly sealed, and best management practices are in place, these structures can offer significant protection from pests and diseases. The cooling of greenhouse structures during the warm months can be very costly, as they offer less insulation than indoor grow rooms and allow for the entry of sunlight. Therefore, of the systems mentioned in this article, Greenhouse structures offer the second-greatest level of environmental control and are suitable for Cannabis grown for smokable flower or the extraction of essential oils.

Shade House, High Tunnel and Hoop House Production

Like greenhouse production, production within shade houses, hoop houses and high tunnels allow for little photocontrol. Natural light entry into these structures can be manipulated by selecting coverings that block out some degree of light, and supplemental lighting can be installed. Traditionally, these structures have open sides, allowing for the entry of pests and pathogens. If these structures are fully encased in plastic, they can provide some physical protection from weather, pests and pathogens at the cost of natural temperature regulation and airflow. Production in these structures is significantly less expensive than production indoors or in greenhouses. If plants are grown in containers, growers can avoid high instances of soil-borne diseases like phytophthora root rot and southern blight. Therefore, it is feasible to produce hemp for smokable flower and essential oil extraction in this system. But farmers should aim to achieve the shortest crop cycle possible to minimize the plants’ exposure to the harsh Louisiana environment and factors such as severe weather, diseases and insect pests.

Field Production

Outdoor production offers minimal photocontrol and no control over temperature or pest pressure. Growers are constrained to natural photoperiods but may install outdoor lighting to extend daylength or implement night breaking. However, this will be very difficult to implement while also maintaining crop uniformity, unless permanent overhead lighting structures are installed to provide uniform lighting throughout the field. Additionally, plants have no protection from plant diseases, such as phytophthora root rot, stem canker, southern blight and Botrytis, all of which are prevalent in Louisiana. Field production is the lowest cost production system included in this analysis and allows for the least amount of environmental control. Therefore, this production system is best suited for the growth of industrial hemp for grain or fiber, where floral quality is not of concern and photocontrol is unnecessary.

Samuel des Bordes is a doctoral student in the LSU College of Agriculture School of Plant, Environmental and Soil Sciences. Heather Kirk-Ballard is the consumer horticulture specialist for the LSU AgCenter and an assistant professor.

This article appears in the fall 2023 edition of Louisiana Agriculture magazine.

Young hemp plants grow in a research project focused on fall plantings of the crop at the AgCenter Doyle Chambers Central Research Station in Baton Rouge. The research is part of the S-1084 multistate hemp project conducted by Babitha Jampala. Photo by Kyle Peveto

Research associate Blake Boatwright installs plastic sheeting for a walkway between newly planted hemp seedlings that are part of a research project at the AgCenter Doyle Chambers Central Research Station in Baton Rouge. This research is a part of the S-1084 multistate hemp project conducted by Babitha Jampala. Photo by Kyle Peveto