Germination and Emergence

Hemp starts its life as a seed. Typically, a good indication of a high-quality seed is a brown, outer waxy coating which is usually hard. Inside hides the dehydrated plant waiting for water and heat. Germination usually takes around 24 hours to 7 days. Seeds are usually germinated before planting on the soil bed.

The goal here is to make the seeds “pop.” That is, cotyledon leaves and a root should start emerging from the seed. This signals that the seed is ready for planting. The optimal temperature during germination stage is around 24º C, but some cultivars are known to survive 0º C temperature. Moisture should not be excessive to avoid growth of mold.

As seeds develop their tap roots, they are not ready to be transplanted to a growing medium, which should be watered to aid the sprouts’ growth.

Vegetative Stage

The vegetative stage is characterized by the growth of stem and leaves.

Seedling Stage (Early Vegetative Stage)

The germinating seeds will now grow into seedlings which typically takes anywhere from two to three weeks. It should be noted that the plant is growing most of its leaves. Initially, leaves with have one ridged finger. However, it should continue to develop more during the following weeks. Mature plants would typically have five to seven fingers per leaf.

At this point, the plant is steadily growing its roots. Watering the plants should only be enough for the roots to seep into the soil. At this point, the plant is vulnerable to diseases and mold. Moisture should be closely monitored.

Seedlings should be short with dense vegetation. The leaves should show a healthy vibrant green color.

Vegetative Stage

At this stage, the hemp plant will start growing its stalks along with most of its leaves. Roots and foliage should be rapidly growing within two to eight weeks after seeding. Ideally, the plant should be transferred into a larger pot or even in soil bed in certain areas and climates.

Water should gradually be increased as the plant and its roots continue to grow. A nutrient-filled soil is ideal for maximum growth.  It is a good idea to increase nitrogen to aid development.

The hemp plant is sensitive to short day length. If the plant is exposed to 12 hours or less of light, it will induce early flowering which will hinder further fiber production. The light should be at least 13 hours or more.

At this point, it is possible to determine whether the plant is male or female as it approaches the flowering stage. Female plants would usually have two hair-life pistils growing on buds. Male plants have little sacs that contain pollen.

The ideal temperature is between 20º C to 25º C. Dampness should be maintained around 50% to 70%. Some cultivars may need additional nitrogen at this stage.

Harvesting Fibre

Hemp fiber is usually harvested 70-90 days after seeding which is typically towards the end of the vegetative stage or very early in the flowering stage. Schedule depends on what type of fiber is harvested.

Flowering and Seed Formation

The flowering stage is the last stage of the hemp plant. Flowering starts once the plant receives less than 12 hours of light during the day. That means, most hemp crops will start to flower at the same period of the year regardless of their seeding schedule. Flowering starts between four to twelve weeks.

Resinous buds will begin to develop and flowering will commence. Male plants will mature earlier than the female plant. Flowers from female plants will start developing earlier than the male plant. Stalk growth will slow down as well.

Seeds will begin to form towards the end of pollination. Seeds will mature after blooming of the flower. They will start to harden and shed which usually starts in three to five weeks. Seed maturity starts when 50% of the seeds are hard or starts to shed.

Ideal temperature should still be maintained between 20º C to 25º C. The humidity should be around 50% with a light cycle of 12 hours a day. Fertilizer with potassium and phosphor is ideal, but no nitrogen is needed anymore.

Harvesting Seeds

Hemp seed harvesting is quite tricky. It requires knowing the crop and the climate of the area. Seeds mature differently between different cultivars. Moreover, seeds mature at different times on the same plant.

A good rule of thumb is to observe when the flowers are ripe. Typically, leaves will begin to wilt or even fall to the ground. In most farms, seed harvesting begins when the plant is about 16 weeks. The trick is to determine the right harvest time with the least seed loss.

Senescence

Senescence, or deterioration, will begin well after the maturity of the seeds of female or monoecious plant or after the flowering of the male plant. Leaves will start to wilt and decompose. Moreover, stems will start to dry.

Final Thoughts

It is important to determine the perfect timing of the cultivars’ growth cycle to the climate of the location. Additionally, it is necessary to determine the perfect harvest time for different kinds of raw products (e.g. seeds, fibre, etc.) and how each cultivar reacts to the weather, temperature, rain, and moisture.

Sources

(1) Allerget, S. 2013. The history of hemp, In: Bouloc, P., Allegret, S., and Arnaud, L. eds. Hemp: Industrial production and uses. Wallingford, U.K.

(2) de Meijer, E. P. M. 1995. Fiber hemp cultivars: A survey of origin, ancestry, availability and brief agronomic characteristics.  Journal of the International Hemp Association  2(2):66-73.

(3) ElSohly, M.A., and Gul, W. 2014. Constituents of Cannabis sativa. In: Pertwee, R.G. ed. Handbook of cannabis. Oxford, U.K.: Oxford University Press, 3-22.

(4) Meidavilla, V., Jonquera, M., Schmid-Slembrouck, I., and Soldati, A. 1998. A decimal code for growth stages of hemp (Cannabis sativa L.). Journal of the International Hemp Association. 65, 68-74.

(5) Meier, Ch. and V. Mediavilla 1998. Factors influencing the yield and the quality of hemp (Cannabis sativa L.) essential oil. Journal of the International Hemp Association  5(1):16-20.

(6) Schreiber, G. 1997. The Hemp Handbook. Munich, Germany: Wilhelm Heyne Verlag GMBH & Co. KG.

(7) Small, E. 2017. Cannabis: A complete guide. Boca Raton: Taylor & Francis.