When it comes to hemp cultivation, there are a few key factors to consider when deciding how far apart to plant your hemp plants. A common practice is to leave 6 feet between rows and 4 feet between plants. This allows for easy access to the rows and plants throughout the season, as well as providing more open space for sunlight. Research conducted at OSU and elsewhere has shown that when plants grow together, the size of the primary tail is not much affected, but overcrowded plants produce fewer side branches and far fewer secondary and tertiary tails.
For full-season types, the maximum total yield of plant biomass per acre is generally achieved when the plantation is dense enough for the plants to pile up a bit as it approaches maturity (the canopy closes completely at the time of the first flowering). Plantations of more than 9,000 plants per acre allow for high biomass production for full-season types (with a distance of approximately 2.5 by 2 feet). At the OSU-Southern Oregon Research and Extension Center, they have studied plant densities of up to 40,000 plants per acre. With such a high density, plants tend to be taller, with a single primary branch and very few lateral branches.
When planting and harvesting hemp in six-foot centers, it ensures that it's easy to walk through the rows because the path is 3 feet wide. This provides more open space for sunlight, as well as a 15% higher plant density per acre than a square or rectangular system design. We have chosen to design the fields using the triangular system, in which the plants are placed halfway between the plants in the adjoining row. If you are mainly cultivating large, high-quality primary flower structures (tails), in addition to maximizing the number of secondary and tertiary branch tails, a wider space between plants encourages more lateral branching and therefore greater production of secondary buds.
When designing a real field for planting and harvesting hemp, adjustments must be made to fences, roads, drains, buildings, ponds, irrigation requirements etc. For example, when plants grow close together in humid climates or are frequently irrigated by an overhead sprinkler system, there is a greater chance of disease problems such as powdery mildew or other diseases that thrive in hot and humid environments. We see commercial plantations of full-season types (sensitive to the length of the day) in a space of perhaps 6 by 5 feet, which is equivalent to only about 1500 plants per acre. The cost or hassle of adjusting these types of physical restraints can nullify the growth characteristics of plants when deciding on planting configurations.
Drip irrigation can help in these situations but wider spacing between plants that allows air movement also delays the transmission of some diseases. Closely spaced plants will produce more branches with more good-quality secondary and tertiary tails while densely spaced plants will produce fewer secondary and tertiary tails per plant but more floral biomass and a yield of extractable cannabinoids per acre. Basal N mineralization refers to the release of available nitrogen in plants that accompanies the decomposition of soil organic matter. When deciding on how far apart to plant your hemp plants, it's important to consider all factors such as access throughout the season, sunlight exposure, disease prevention and yield potential.
Planting hemp in six-foot centers ensures that it's easy to walk through the rows while providing more open space for sunlight and higher plant density per acre than other system designs.