The characteristics of hemp seeds: morphology, genetics, and categorization

Understanding the differences between the various types of Indica, Sativa, and Hybrid hemp seeds and feminize the seeds for better yield

Hemp seeds genetics – The three main groups: Indica, Sativa and Hybrid

There are different genetic types of hemp seeds generally divided into three main groups: Indica, Sativa, Hybrid. A classification that has existed since the 18th century, a time when the first taxonomic distinctions were made, when differences were noted between their structure and resin production. The Hybrid category came about as a result of the different mixes of genetics from different geographical locations made by growers around the world.

The Indica Hemp

Normally, an Indica Hemp plant is recognizable by its small, bushy shape with stubby, dark green leaves. The effects attributable to the Indica variety are sedatives with high medicinal value, and can be used to relieve pain or to help sleep. Morphologically, they tend to stay below 1.20 meters in height, making them particularly suitable for growing in small spaces. Pure quality Indicas from Afghanistan have contributed to the evolution of contemporary culture and the spread of hemp. In these parts of the Middle East, in the Hindu Kush region, this variety has developed thick layers of resin to protect itself from harsh climatic conditions.

Sativa Hemp

Sativa is the type of hemp famous for its energizing, stimulating, psychoactive effect, aand for its action on cognitive function. This variety grows with speed and can reach three to five meters in height.

Hybrid Hemp

Most modern genetics on the market are Hybrids, meaning that part of their genetic makeup is derived from Indicas and part from Sativas. The growth of such variants can be influenced by the dominant genes they have inherited. The content of active ingredients and terpenes also affects the final effect generated in the plant: the best known ones are THC (delta-9-tetrahydrocannabinol) and CBD (cannabidiol).

Characteristics of hemp seeds: color, size and shape

The color and texture of a seed can suggest the degree of maturity of a healthy plant and its potential to germinate or grow. Mature hemp seeds have a tough outer shell with a color that can range from dark, almost black, to light gray and may also have tigerish streaks.

To the touch, ripe seeds, when pressed between the fingers, are tough and resilient. In contrast, unripe seeds exhibit a green color and have a soft outer shell that breaks when pressure is applied.

The packaging and storage process of seeds can affect their appearance. Although not affecting their quality, sudden changes in humidity, temperature, or exposure to light can make some seeds appear darker or lighter than others.

Hemp seeds are biologically different from each other, although belonging to the same strain they show different physical characteristics. The natural differences that characterize a larger, rounder, darker seed from a lighter, smaller, more oval-shaped one do not qualify it as a seed of better quality.

Recognizing the sex of hemp seeds: male, female or hermaphrodite

Hemp species are divided into two primary groups: monoecious species-which have a single genus, i.e., a plant that carries within itself, both the male and female genetics-and dioecious species, where for each species, there subsists the male and female types.

It is scientifically recognized that the sex of a hemp plant cannot be determined until a couple of weeks after flowering. The only way to distinguish a female plant from a male is by the inflorescences. Only female seeds produce the flowers, called buds, which are the part of the plant richest in resin and therefore cannabinoids, while male seeds produce plants that produce pollen sacs at the base of the leaves. The first differences between male and female plants can be seen when they are in the preflowering stage, as thin, white pistils begin to appear in the female plants.

Feminizing hemp seeds

Feminized seeds are seeds genetically programmed to generate 99% female plants. In countries where hemp cultivation is legal, several techniques are used in order to feminize seeds. The first technique is the one called Rodelization Feminizing, which involves subjecting the seed to a level of stress such that the light cycle is interrupted right at the flowering stage. The second technique, the one most widely used, involves spraying the female seedlings with a special solution containing silver and sodium trisulfate, again during the flowering phase. This solution has the ability to inhibit ethylene, which is the hormone involved in flowering, so the plants will begin to produce flowers with pollen sacs at the base of the leaves.

The flotation test to determine hemp seed quality

There is a test believed to be almost foolproof for determining whether hemp seeds are capable of germinating: immersion in water. If by placing the seeds on the surface of a glass of lukewarm water (preferably mineral or distilled) the seeds float, it means they are dead or poor, while if they go down it means they are of good quality.

Seeds that sink are probably healthy, and can be set to germinate. Good quality seeds that have gone to the bottom will have absorbed water, which upon penetrating through the seed membrane will have activated germination. The results of the flotation test do not appear immediately, as one must wait approximately two hours before the quality of the seeds can be confirmed, using seeds scheduled to germinate later.

Seeds categories: regular, feminized, autoflowering

In nature, the hemp plant adjusts its growth and flowering cycle according to sunlight: by sowing the plant in spring, when the days get longer and the sunlight warms the earth for more than twelve hours, the plant is in the vegetative growth phase, not producing flowers but developing roots, leaves, and stem. As the warm season passes, towards the end of August, when the days begin to shorten and there is less than twelve hours of light, the female hemp plant ends its life cycle as it prepares for the arrival of winter. It is only at this point that it will begin to flower in order to ensure the survival of its genes.

Plants in nature therefore follow the photoperiod, which is the sunlight cycle. In indoor cultivation, it is the lamps that tell the plant when to grow and when to flower, determining up to an intake of nineteen hours of light. To induce the plant to flower, the lamps will need to be increased to less than twelve hours of light. A variation of this cycle occurs with Autoflowerings, a type that does not follow light hours but adjusts its life cycle according to a well-defined time frame.

Photoperiodic seeds

Regular photoperiodic seeds, subject to light variations, can produce both male and female specimens. Experienced growers prefer them, although they must then select and separate opposite-sex specimens to avoid pollination of females, claiming that the quality of plants born from these seeds is far superior to that of feminized seeds. They also may decide to obtain new seeds by pollinating the females. Regular autoflowering seeds have a time life cycle so they do not need to follow a light cycle. However, these seeds are in low demand and are produced by few seed banks.

Autoflowering feminized hemp

Autoflowering feminized hemp has a well-defined life cycle and begins to flower spontaneously after about four weeks. Timing varies according to genetics. Photoperiodic feminized seeds that have shorter flowering times are the F1 or Fast Version type. This version is photo-dependent and fast flowering. Although these varieties are suitable for growing in humid, rainy, high mountain areas or with cold winters, this is a type that is susceptible to fungal attacks because their harvesting can anticipate the more virulent botrytis (gray mold), which decimates the tops of slower flowering plants.

A seed variety peculiar to the Piedmont region: Carmagnola

There is an Italian variety of hemp, Carmagnola, which belongs to the strain of varieties produced in Italy along with Carmagnola Selezionata and Fibranova. Cultivated for centuries, Carmagnola has genetics developed to produce biomass. It is also a dioecious species, meaning that it has both distinct male and female individuals, and in terms of seed and inflorescence it produces satisfactory quantities. It is robust, with high CBD and low THC content, and is adapted to colder and harsher climates. It is the only known Landrace in the world other than wild hemp growing in Nepalese territory.

The name comes from an area a few kilometers from Turin, Carmagnola, near St. Bernard, an area that over the centuries has consolidated hemp cultivation and an international production of raw fiber and ropes. A thriving trade, hemp farming endured until the mid-20th century. As of June 2021, the three varieties were excluded, extinct from the market. When a hemp variety is no longer regularly included in the list of seed varieties approved by the European Union, it automatically loses the right to be allowed for cultivation, therefore, it will need ministerial authorization to be grown.

Martina Tondo