Hemp Production in Louisiana

The 2018 Farm Bill has created substantial interest in the production of hemp (principally Cannabis sativa) in Louisiana and elsewhere in the United States. This interest is mostly focused on the extraction of cannabidiol (CBD) oil from the floral buds which has numerous therapeutic anecdotes. Additional, legal uses of hemp are due to the fibrous nature of the stems and includes such products as textiles and paper, plastics, fuel, and as a food. In Louisiana, hemp plants with less than 0.3% THC (tetrahydrocannabinol) are now allowed for field production with the proper permits. Available information on how to grow hemp in Louisiana is scarce.


Hemp (Cannabis sp.) is a member of Cannabaceae family and includes several species, e.g. C. sativa, C. indicia, and C. ruderalis. Commercial cross-bred hybrids between the species are available. This is of interest since while both C. sativa and C. indica may contain up to 29% by weight of THC, C. ruderalis has negligible amounts of THC but is high in CBD (up to 40% of all cannabinoids in the plant). Cannabis sp. origins have been attributed to Central and/or South Asia, notably China. The word “hemp” has generically been used to describe numerous other plant species that produce strong fiber: e.g. Manila hemp (Musa textilis); sisal hemp (Agave sisalana) and sunn hemp (Crotalaria juncea) as examples (Dempsey, 1975).

Hemp is an annual plant that generally has separate male and female plant types (dioecious) and dioecious types are preferred for most uses. Interest is almost exclusively on the female plant types. There are monoecious types with both male and female parts on the same plant and are mostly of interest in paper and pulp production. Sex determination may be modified by environmental conditions. It can also be manipulated by the application of certain chemicals.

Leaves are palmate and have serrated edges. Plants can attain heights of 13 feet. .Since male and female plants are separate, pollination occurs by wind. The plant is normally considered to be a short-day plant: it only flowers when night lengths exceed a critical photoperiod (hours of daylight). This means that flowers will not be produced until sometime after the summer solstice as nights begin to get longer (12+ hours of darkness) – possibly not until 1 August.There are also day-neutral varieties of hemp and these will probably be of most interest to producers in Louisiana since photoperiodism is not important for flower/bud production but rather the attainment of a certain developmental stage or age induces flowering.


While hemp can be grown hydroponically, this is largely going to be for medicinal uses focusing on plants with a high amount of THC. For CBD and other uses, field cultivation is more likely and has a lower cost of production. For field production, soil pH should be between 7.0-7.4, high in organic matter, and well drained (water logging or water saturated soils are detrimental). The optimum growth temperature is between 75-86 degrees F with a humidity of 40-60%.The plant does not tolerate heavy or repeated frosts. General soil fertility should be high in N (nitrogen) and K (potassium) macro nutrients as well as a complete micro nutrient fertilizer. Planting will commence in mid-April through late May and plants will grow up to 4-5.5 months (Dewey, 1913). Staggered plantings should allow for sequential harvesting.

Guidelines for field cultivation in Louisiana are not available. Several earlier studies suggest fall plowing to a depth of 20cm along with the application of organic manures. Data from Kentucky suggest a seeding rate of ~40 pounds per acre (45kg per hectare) drill planted on rows from 8-16 inches (5.5 – 11cm ) apart. This rate was shown to give approximately 200 plants per square meter that, by harvest time, had reduced to a more desirable final plant population of 120-150 plants per square meter. Higher rates may be desirable (e.g. 500 plants per square meter) to maximize fiber production and make the crop more suitable for mechanical harvesting.

Seed size is variable, from 44,000 – 70,000 per kilogram for cultivated varieties. Fungicide treatment of seed may increase germination over untreated seed. Suggested fertilizer rates are 50-100lb applied N and soil test results of available P and K of 60lb and 300lb K per acre, respectively. In comparison to grain crops, hemp’s N,P and K requirements as 2,3 and 6 times as much, respectively. Adequate soil moisture is essential for establishment of a good stand. Soil temperatures of >50oF should be available at planting. Seeding depth is shallow, never to exceed one inch. Additional information is available from the publication: An Introduction to Industrial Hemp and Hemp Agronomy. Univ. of Kentucky. ID-250.

The seedling stage typically lasts up to 4 weeks and is the most vulnerable plant stage. Hemp then enters a vegetative stage that lasts 1-2 months. Cultivation needs of the crop are minimal unless plant populations are low since shading of competitive weeds will be achieved once the crop reaches 50 cm in height. A pre-flowering stage referred to as ‘stretch’ lasts for 1-2 weeks and the plant will grow rapidly. The stretch phase ends when the plant is induced to initiate flowering due to photoperiod or developmental age. The sex of a hemp plant can be inferred by plant height: females tend to be shorter and have more branches than males. Females also have a raceme type inflorescence while male flowers are borne on panicles. In commercial production settings (notably for seed), males are typically removed as soon as they are identified. This allows the female racemes to not be pollinated and the buds produced will lack seeds (“sin semilla”).

Flowering itself will take place over a period of 6-22 weeks (on the longer side in C. sativa) with hybrids having a more intermediate flowering period. As mentioned previously, males are typically removed as soon as they are identified. Doing so induces later female flowers to produce buds with an increasing amount of resinous trichomes in an attempt to attract pollen. These are particularly high in the psychoactive components THC and cannabinols. To induce greater bud formation, plants may be ‘topped’ to remove the apical meristem. Excessive topping and pinching will produce inferior buds.

Harvesting is largely a matter of harvesting the buds, which may be done by hand or mechanically. Determining when buds are ripe is an effort to maximize levels of CBD but before they begin to degrade. Buds with clear trichomes (as seen under a 30-60x microscope) are immature; white or cloudy trichomes are at the maximum level of total cannabinoids (THC and CBD); amber/purple trichomes indicate degradation of THC to CBD and an increase in CBD. After harvest, the buds are dried, ideally between 60-70oF. Higher temperature drying (e.g. 110oF) may reduce drying times and produce a more stable product. Temperatures above 70oF cause terpenoids (such as CBD) to evaporate. Drying to the desired 8-14% moisture can take a few days and ideally no more than 7 days.High humidity can induce molding and possible rejection of the crop. Excessive drying times can lead to a buildup of toxins and undesirable compounds.

Growing hemp for seed

Hemp grown for fiber will be harvested before hemp that is being grown for seed. Consequently, if seed production is important this will be done separately. Hemp being grown for seed is grown at a much wider spacing of 1-1.5 meters apart between and within rows. Hemp grown for seed is typically planted in hills and the seeding rate is only 1-3 kg per hectare. Hills are typically sown with up to ten seed per hill, later thinned to 3-5 plants once plants reach 3-8 cm in height (Dempsey, 1975). Due to the wider spacing, more frequent weed cultivation is needed or mulches may be used. In seed production systems, the early removal of male plants is important – only one or two males per 25 square meters is desired. Once the males have shed pollen, they are also removed. Data from some European countries suggest higher seeding for hemp being grown for seed: ~15-25 kg per hectare of seed on rows 12 - 50 cm apart.

Harvesting of hemp being grown for seed begins about 40 days after pollination.Hemp seed will develop from the base of the plant towards the top and are prone to shattering. As a result, harvesting tends to occur in the morning when humidity is high to minimize shattering losses. The stems are cut just below the lower branches leaving 40-69 cm of stubble.The stems are bundled and shocked for drying which takes 3-5 days. Seed can be used as a protein source. The chaff contains useful levels of cannabinoids.

Growing hemp for fiber

Timing of harvest for hemp being grown for fiber is important. Too early of harvest will produce low yields of weak fiber. Delayed harvest will produced course fiber. In a dioecious hemp crop harvesting when about 50% of the male plants have become yellow or when the bottom two-thirds of the male and female plant stems have lost their leaves. Fiber production can exceed 3,000 kg of retted fiber per hectare.


Dempsey, J.M. 1975. Fiber Crops. Univ. of Florida. 457pp.

Dewey, L.H. 1913. Hemp. pp. 283-346. USDA Yearbook.

8/13/2019 4:19:14 PM
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