Hemp Cultivation methods vary depending on the purpose of the crop – food, fibre or flower.
Hemp is generally a low maintenance crop which performs best with good nutrition, irrigation and weed management.
Hemp Cultivation Overview
Growing Hemp for Food, Fibre and Flower
Hemp (Cannabis sativa L.), aka Industrial Hemp is an annual, herbaceous plant with a slender stem, ranging in height from 1 to 6 metres and with a stem diameter of 10mm to 30mm.
Plant habit varies widely depending on cultivar and cultivation methods used. Leaves are a distinctive palmate shape with 5 to 11 leaflets and serated edges.
Best Soil Types for Hemp Cultivation:
Hemp can be grown on a wide variety of soil types. Sandy Loams are ideal, but hemp will thrive in most soils which are deep and well aerated and drained with the right inputs. Different hemp cultivars have their own soil type preference.
Soil is normally grown from direct planted seed for grain and fibre production.
In contast, medicinal hemp varieties are generally propagated in a nursery and planted out once they have hardened, typically at 15 to 30mm in height.
Nutrition for Hemp Crops
While hemp will tolerate poor soils and low planes of nutrition, commercial production will reward sensible nutrient inputs.
Hemp farmers should consult qualified agronomists to test soil and advise on inputs to optimise growth and production.
Note that for medicinal use hemp should be cultivated as a cannabis crop – and often the genetics of high CBD hemp cultivars owe more to medical cannabis than industrial hemp.
A strong understanding of the preferred inputs for the cultivar and production method selected is essential.
Weed Management for Hemp Crops
Mature high density plantings of industrial hemp will suppress weeds, but good weed control prior to and during seed emergence and establishment.
For medicinal hemp production the wider spacing requires similar weed control measures to other horticultural crops.
Best Time to Plant Hemp Seeds
Depending on the local longitude, climate and weather patterns hemp is typically planted around May in the Northern Hempisphere and around November in the Southern Hemisphere. In tropical and subtropical climates, two or more crops of industrial hemp may be possible, but finding locally adapted hemp cultivars which perform well can be difficult. Autoflower strains are showing promise for extending the growing season in different regions
Best time to Harvest Hemp Crop
Harvest time for hemp crops varies according to the crop type.
Fibre crops are normally harvested early, before seed set.
Hempseed grain or hempseed oil crops are typically harvested once seeds are mature, but before birds and pests damage the crop (sometimes a narrow window).
Hemp Flower types are harvested accoridng to the desired cannabinoid profile. Ideally, flowers would be harvested at maximum resin production but this will typically result in THC content exceeding legal limits.
As a result hemp flowers are normally harvested when CBD levels reach acceptable limits but before THC crosses the threshold.
This can be a significant balancing act and careful crop management and testing from experienced farmers is essential to maximise crop value and avoid loss of product due to exceeding THC limits.