How is industrial hemp grown?

• What is industrial hemp?
• Industrial hemp varieties
• How is hemp grown?
  1. Soil preparation
  2. Sowing
  3. Care during growth
  4. Removing male plants
  5. Harvest
• Growing hemp for specific purposes
• The most common problems when growing hemp
  • Unsuitable conditions
  • Pests
  • Diseases
• Current legislation
• Conclusion
• FAQ

Disclaimer: This article refers exclusively to industrial hemp cultivated and used following applicable legal regulations. The content is provided for informational purposes only. It does not promote or encourage the cultivation or production of controlled substances, nor does it support any illegal activity or replace individual legal advice.

What is industrial hemp?

Industrial hemp, Latin name Cannabis sativa L, is a variety of hemp that is cultivated for economic, industrial, food and medicinal purposes. Unlike marijuana, it is bred to contain only minimal amounts of THC, the substance responsible for the psychoactive effects of marijuana.

The THC content of industrial hemp is regulated by individual states and ranges from 0.2% to 1% depending on the legislation.

Industrial hemp varieties

Hemp is an undemanding, hardy and high-yield plant, every part of which can be used. There are dozens of varieties that differ in height, branching density, yield, cannabinoid content, growing season length and suitability (i.e. their uses).

Individual regions, such as the European Union or the United States, have their own list of permitted varieties that meet the maximum permitted THC limit. Growers purchase certified seeds from specialised distributors. This guarantees that the plants grown will be of high quality, correspond to the description and do not exceed the permitted limit.

When selecting a variety, it is particularly important to consider whether the plant is to be grown for fibre, seed, flowers or multiple purposes.

• Fibre varieties: These varieties have tall, slender stems and little branching. They include Futura 75, Carmagnola and Zolotonosha.
• Seed varieties: Medium-sized varieties with more branched tops that produce larger inflorescences with higher seed yields. These include Finola, Ferimon and Henola.
• Varieties for flowers and cannabinoids: Lower to medium-tall branched plants with compact flowers and a distinctive aroma. Popular varieties include Tiborszállási and Santica 70.
• Multipurpose varieties: These have medium to tall growth and the individual parts of the plant have a balanced yield. These include Kompolti.

 

How to grow hemp

Hemp thrives in a temperate climate with plenty of sunlight. The ideal temperature during growth is between 20–30 °C during the day, with slightly lower temperatures at night.

Hemp needs as much direct sunlight as possible, so it is best to place it on the south-east or south-west side. It is also important that the location is airy, as dense vegetation can be prone to mould.

Deep, permeable and fertile soil that is neutral to slightly acidic is suitable for growing hemp.

1. Soil preparation

It is best to prepare a suitable location in autumn — remove weeds, residues from previous crops, dig or plough the field, and, if necessary, work in organic fertiliser to ensure sufficient nitrogen and potassium. In spring, the soil only needs to be levelled, sprinkled with lime if it is too acidic, and then it is ready for sowing.

2. Sowing

Industrial hemp can be sown directly into the soil, or the plants can be pre-grown and then planted. Sowing takes place from late April to mid-May, when the soil is warm and there is no risk of frost.

The seeds can be soaked in lukewarm water for several hours before sowing to speed up germination. The seeds germinate within 2 weeks.

3. Care during growth

Young plants are most susceptible to weeds and pests. Therefore, it is necessary to regularly remove weeds and check the hemp. Water and fertilise as needed.

4. Removing male plants

Industrial hemp varieties are not feminised as standard, which means that both male and female plants will grow from the seeds. If the intention is to grow hemp for seed, it is necessary to have both male and female plants so that pollination can occur and seeds can form.

However, if the purpose is to obtain flowers rich in cannabinoids, it is necessary to grow seedless buds. Therefore, it is necessary to remove male plants. The sex of the flowers can be recognised approximately 5-6 weeks after sowing — small round pollen sacs begin to form on male plants. These plants need to be pulled out or cut off at ground level and disposed of outside the growing area to prevent pollination.

5. Harvest

The harvest date depends on the cultivation purpose and the variety grown.

If the aim is to obtain fibre, hemp is harvested during the flowering period, approximately 5-7 weeks after sowing, before the seeds form. At this time, the fibre has the best properties — it is long, strong and flexible. Harvesting is done by cutting the entire plants, which are then left lying in the field for 2–3 weeks to allow them to partially decompose and the fibres to be easily separated.

Hemp grown for flowers with a high cannabinoid content is harvested at full maturity, approximately 8–10 weeks after sowing. The flowers should be compact, sticky and aromatic. Immediately after harvesting, the flowers are slowly dried.

If hemp is grown for seed, it is harvested approximately 10-14 weeks after sowing, depending on the variety and conditions. Ripe seeds are hard, brownish-grey in colour and begin to fall out of the buds. After harvesting, the seeds must be dried thoroughly immediately, otherwise they can quickly become rancid or mouldy.

 

Growing hemp according to purpose

Choosing the right variety and understanding the entire growing cycle are key to successful industrial hemp cultivation. The following table summarises the key aspects of cultivation and harvesting depending on the purpose.

Purpose	For fibre	For flowers and cannabinoids	For seeds	Multi-purpose
Examples of specific varieties	Futura 75, Carmagnola, Zolotonosha	Finola, Ferimon, Henola	Tiborszállási or Santica 70	Kompolti
Key characteristics of the varieties	Tall, slender stems with minimal branching	Shorter to medium height, branched plants with compact flowers and a strong aroma	Medium stature, more profusely branched tops, producing larger inflorescences	Medium to taller growth with a balanced yield of fibre, seeds and flowers
Harvest time from sowing	5-7 weeks	8-10 weeks	10-14 weeks	Depending on the harvest objective (flowers, fibre or seeds)
Usage	Textile, construction	Flowers, CBD products (extracts, oils, dietary supplements, vapes, cosmetics, etc.)	Food and cosmetics industry	Miscellaneous

The most common problems when growing cannabis

Although cannabis is an undemanding and hardy plant, complications can arise during cultivation, caused, for example, by unsuitable growing conditions, pests or diseases.

Unsuitable conditions

The environment in which the plant grows has a significant impact on the growth and quality of industrial hemp. Even minor deviations from optimal conditions can cause stress, slow down development or reduce yield.

• Incorrect temperature: The ideal temperature for growing hemp is between 20–30 °C during the day. If the temperature is lower, hemp grows more slowly; if it is higher, photosynthesis slows down, which can lead to lower yields — small buds with lower cannabinoid content and poorer seed quality.
• Inappropriate air humidity: High air humidity increases the chance of mould growth, while excessively dry air can increase the risk of sucking pests.
• Excessive or insufficient watering: Overwatering can lead to root rot and plant death, while a lack of water causes slow growth and leaf drying.
• Over-fertilisation: An excess of nutrients can lead to excessive plant growth at the expense of flower and seed formation. Excessive fertilisation can lead to the growth of fragile stems and damage to roots and leaves.
• Lack of nitrogen or potassium: Nitrogen is crucial in the first phase of growth, and if the plant does not have enough of it, it grows more slowly. Potassium is essential for flower and seed development and for the plant's resistance to stress and disease. Its deficiency manifests itself in weaker flowering, poor seed formation and yellowing of the leaf edges.
• Unsuitable soil pH: Soil with a neutral to slightly acidic pH is suitable for growing cannabis. Soil that is too acidic or alkaline limits the absorption of certain nutrients, leading to deficiencies despite adequate fertilisation.

Pests

Perhaps the greatest threat to germinating plants are slugs, which can completely destroy them within a few hours. It is therefore important to remove egg deposits from the soil before sowing and protect the bed with a strip of coarse sand or lime.

It is also important to check the bed regularly and remove slugs. To be on the safe side, young seedlings can be grown in pots at first and only planted outside when they are stronger.

Although hemp repels many pests due to its strong aroma, there are some insects that still attack the plant. The most common are:

• Aphids: They suck the sap from the leaves, which then wilt and dry out.
• Spider mites: They create white dots and fine webs on the leaves and weaken the plant.
• Thrips: They nibble on the leaves.
• Whiteflies: They feed on leaves and stems.

If pests appear, it is necessary to remove the affected parts or entire plants and shower the other plants and treat them either by spraying or by introducing natural predators that will destroy the insects without harming the plants.

 

Diseases

Although hemp is resistant, if the vegetation is dense and humidity is high, it can be attacked by mould. It is therefore important to ensure proper air circulation.

The plant is most commonly attacked by grey mould, which causes bud rot — the buds begin to soften, turn brown and develop a coating.

If the cannabis starts to mould, it is necessary to immediately destroy the affected parts to prevent the mould from spreading and to reduce the humidity.

Current legislation

The legal regulation of cannabis cultivation varies from country to country. In most countries, legal cultivation requires the use of registered and certified varieties and compliance with certain administrative requirements.

In the European Union, it is currently possible to grow cannabis with a THC content of up to 0.3% in the dry plant. Some EU countries allow an even higher limit of up to 1%.

In the United States, the Farm Bill was passed in 2018, legalising the cultivation of industrial hemp with a THC limit of 0.3%. The same limit applies in Canada. In many Latin American, African and Asian countries, regulations vary and are often still being developed.

Conclusion

Cannabis is a versatile crop that has been used by humans for thousands of years in industry and medicine.

There are dozens of varieties of industrial hemp that are bred for different purposes and do not exceed the maximum permitted limit of psychoactive THC. Cultivation is relatively undemanding — hemp grows quickly, is hardy and can be processed without waste.

The cultivation method and harvest time vary slightly depending on the desired result — while only female plants are grown for flowers and cannabinoids and harvested when fully ripe, male plants are also needed for seed production and are harvested at the end of the growing season.

 

Author: Natálie Kubíčková

 

   

Photo: AI

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