Photoperiod-dependent seeds

Photoperiod-dependent cannabis seeds produce plants that flower based on the amount of light and darkness they receive (photoperiod).

Photoperiod-dependent strains start flowering depending on the hours of light and darkness they are exposed to. This group includes all feminized or regular genetics we used to grow before the arrival of autoflowering genetics. When grown outdoors, these genetics flower during a specific time of the year, when daylight hours decrease, and nighttime hours increase, at the end of summer and into fall. Indoors, under artificial lighting, they typically flower when provided with a photoperiod of 12 hours of light and 12 hours of darkness.

The vast majority of cannabis strains are photoperiod dependent. The onset of flowering is triggered by the arrival of shorter days and longer nights. It is the photoperiod that regulates and determines the start of flowering.

Photoperiod-Dependent or “Feminized Seeds”?

Photoperiod-dependent cannabis seeds are often mistakenly referred to as "feminized seeds" by many seed banks and cannabis users, but this is an incorrect usage of the term. The definition of "Feminized Seed" refers to the sex of the seed population. These are seed populations that produce only female plants, known in genetic terminology as gynoecious lines. These seeds are called "feminized seeds" to distinguish them from the seeds known as "regular seeds," which produce both male and female plants. The term "photoperiod-dependent seed" or "autoflowering seed" refers to the two ways in which flowering is triggered in cannabis plants—either depending on the photoperiod in the case of photoperiod-dependent strains or automatically when the plant reaches a certain age in autoflowering strains. In other words, a strain is either feminized or regular, and, at the same time, either photoperiod-dependent or autoflowering. However, it is not correct to call "feminized seeds" to photoperiod-dependent cannabis seeds, because autoflowering seeds can also be feminized, as is the case with all the autoflowering strains in the Sweet Seeds® catalog.

The F1 Fast Version® strains are the first filial generation (F1) resulting from the crossbreeding (hybridization) of a photoperiod-dependent genetic line with an autoflowering genetic line. The result of this hybridization between two completely different plants (at least in terms of flowering type) is known in genetic terminology as an "F1 Hybrid." These are 100% photoperiod-dependent hybrid genetics, but with a very fast flowering cycle. The photoperiod-dependent parent passes on its photoperiod-dependent trait to the entire offspring, while the autoflowering genetic line contributes to the F1 hybrid by providing a very fast flowering and bud maturation in all the offspring.

F1 Hybrids combine, within the same generation, the highly valued "stability" along with the sought-after "hybrid vigor."

These faster strains represent a significant saving in time, resources, and effort. Furthermore, the fast flowering of these genetics is a key advantage for growers cultivating in humid and rainy areas or regions with harsh winters. These marijuana plants can mature before the most aggressive mold attacks or the onset of bad weather and cold temperatures.

Just as autoflowering seeds offer certain advantages over photoperiod-dependent cannabis seeds, photoperiod-dependent seeds also have distinct advantages over autoflowering seeds. Below are the main benefits:

• Preservation of Mother Plants: One of the primary advantages of photoperiod-dependent cannabis seeds is the ability to preserve clones of any special plant we find, indefinitely, as long as they are kept under appropriate light conditions. This is typically achieved by keeping the clones under artificial light with a photoperiod of 18 hours of light and 6 hours of darkness. With this photoperiod, the plants remain in a vegetative state without ever entering flowering and can be used to extract clones from them.
• Vegetative Propagation: Photoperiod-dependent plants can be multiplied in your garden by simply taking cuttings from seed-grown plants or mother plants.
• Control of Height, Size and Yield: By maintaining photoperiod-dependent plants in a vegetative growth photoperiod for as long as needed to achieve the desired height, you can control the height and overall size of the plants, leading to large plants with high bud yields. This allows outdoor growers to produce their annual supply of cannabis with just a few plants. Similarly, by controlling the photoperiod to induce flowering with minimal growth, you can achieve the opposite effect—small, discreet plants with a short life cycle. To plan the desired height, it is important to consider that, depending on the strain, plants can double, triple, or even quadruple their height from the start of flowering or from the moment the photoperiod is changed in indoor grows.

Due to an unfair prohibition and the phenomenon of globalization, both wild and domesticated cannabis strains have been suffering a massive extinction over the past 100 years. For many of these unique cannabis strains, it is already too late and it is impossible to recover them. This loss of biodiversity is inexcusable and represents an immense loss of natural resources for the planet. The unique genetic code of each strain serves as a living laboratory, which could open the door to major discoveries and provide valuable solutions to the significant medical, energy, and industrial challenges humanity will face in the 21st century.

At Sweet Seeds®, we believe the best way to protect cannabis for the future—once this unjust and irrational persecution of the plant ends—is to preserve and increase its diversity while sharing its seeds.

Our breeding philosophy is simple: the breeders at Sweet Seeds® are cannabis enthusiasts and genetic collectors. We search for and select the best genetics we come across to preserve them indefinitely, allowing us to enjoy them today, tomorrow, and for the rest of our lives. We work with the conviction that 200 years from now, future generations will benefit from our work, which is also our great passion at the same time.

The criteria we use to select our best mother plants are based primarily on the desirable qualities of these plants rather than their origin, provenance, or pedigree. The parental plants we use at Sweet Seeds® are the result of 20 years of searching, selection, preservation, and development.

High-yielding plants with abundant flowers and trichomes, combined with unique and pleasant aromas, have always been hallmarks of our genetic collection.

Sweet Seeds® is a pioneering seed bank in the development and improvement of modern feminized photoperiod-dependent cannabis strains. We have believed in these new feminized genetics since the first time we managed to reproduce our beloved female plants by crossing them with each other, creating our first feminized seeds.

Sweet Seeds® strains are the result of classic breeding programs. These programs involve crossing, reproducing, and selecting various genetics until achieving satisfactory results aligned with the intended goals. The purpose of these breeding programs is to select and stabilize desirable traits—whether agronomic, botanical (internodal distance, bud density, etc.), chemotypic (cannabinoid and terpene profiles), or organoleptic (flavors and aromas)—while eliminating any undesirable traits, if present.

The Sweet Seeds® breeders always paid a very special attention to the selection and stabilization of organoleptic traits. All our strains are especially aromatic and flavorful, which is a hallmark of our seed bank and the reason behind the name “Sweet Seeds®.” For us, taste and aroma are just as important as cannabinoid levels, resin production, and other desirable traits.

Sweet Seeds® uses selected “elite clones” for the production of feminized photoperiod-dependent cannabis seeds intended for commercial sale. Clonal selection is a fundamental aspect of breeding programs for most cannabis genetics.

Elite clones are the result of an intensive work of selection, through the identification of the best specimens at the end of breeding programs or through the search and collection of exceptional new genetics. These clones are used as the starting material in breeding programs. Elite clones are preserved in our “bank of mothers” and represent the best female cannabis plants we have encountered throughout our journey as growers, breeders, and genetic collectors. In addition to having numerous appealing traits for cannabis growers, these elite clones must demonstrate a strong capacity for creating high-quality hybrids and respond well to the sex-reversal technique needed to produce feminized seeds.

For the commercial seed production of each strain, the same elite clones are always used. Using consistent parental plants has its advantages: the results are entirely predictable, as they are known in advance and remain the same, allowing us to guarantee the quality of the seeds without variations in the main characteristics of the plants. Only in cases where we find an elite clone that contributes superior traits to the offspring while maintaining the characteristic features of the strain would we consider replacing a parental plant, though this is not a frequent occurrence.

Conversely, when working with autoflowering genetics, it is not possible to preserve the best specimens through cloning. The breeders of autoflowering strains must work with seed populations, which requires constant selection of parental plants both during breeding program development and every time commercial seeds are reproduced. Depending on the chosen parental plants in each generation, these populations can experience genetic drift, causing shifts in traits and preventing consistent gene frequencies in the commercial seeds. In recent years, autoflowering seed populations have been in continuous evolution and improvement.

Our F1 Fast Version® seeds represent the first filial generation resulting from crossing an elite clone from the Sweet Seeds®’ bank of mothers with a selected genetic line of the latest generation of autoflowering seeds. These are F1 Hybrids. Only this first generation is marketed, as it is the only one that is 100% uniform for the photoperiod-dependent trait and 100% fast-flowering. While the process is relatively straightforward, the challenge lies in selecting the parentals. The plants used by Sweet Seeds® as parentals are the culmination of 20 years of searching, selection, preservation, and development.

The most commonly used technique in the development of our photoperiod-dependent strains is hybridization, which aims to improve hybrid vigor and ensure uniformity in the offspring.

Hybridization is one of the most important and productive methods of genetic improvement and one of the most widely used by cannabis seed banks. It allows the desired traits of both parentals to be quickly combined while achieving the primary goal of leveraging the phenomenon of hybrid vigor or heterosis. This hybrid vigor is typically expressed in quantitative traits—measurable characteristics—and in cannabis, it is commonly observed as:

• Increased yield
• Better adaptation to the environment
• Greater resistance to pests and diseases
• Higher tolerance to environmental stress
• Faster growth rates
• Greater precocity (shortened time to reach maturity)
• Increased size overall, including buds, stems, and leaves
• A higher number of nodes, leaves, flowers, trichomes, etc.
• Increased total quantity of terpenes and cannabinoids

Not all vegetal species exhibit the phenomenon of hybrid vigor, but it is quite common in the plant kingdom. Fortunately for us, it is expressed most strongly in allogamous species, which is the case of marijuana, and the heterosis or hybrid vigor is more pronounced when there is greater genetic distance between the plants used as parentals.

In contrast to hybridization, self-pollination is used to reproduce the unique and desirable characteristics of an elite clone without introducing external genetics. This technique provides great stability in the offspring and also in the successive generations.

This technique was used in the development of one of our first feminized photoperiod-dependent strains: S.A.D. Sweet Afgani Delicious S1® (SWS02).

Self-pollination results in seed generations that rapidly become homozygous. It is one of the traditional methods used to create pure lines in allogamous plants like cannabis. With each generation of self-pollination, 50% of the heterozygous genes become homozygous.

The technique we use to achieve self-pollination of a female clone is the same technique employed to produce feminized seeds. It involves obtaining viable pollen from a female clone and using this pollen to pollinate another female clone of the same mother plant. To collect pollen from female plants, we apply a sex-reversal product based on silver thiosulfate. This application induces the production of male flowers in female plants. With the appropriate dosage and method, it ensures abundant and viable pollen production from a female plant.

Self-pollination is a relatively recent technique in cannabis strain improvement. Before the discovery of sex-reversal techniques, it was impossible to apply these techniques of improvement without dragging genes of hermaphroditism towards the offspring. The only way to self-pollinate a female cannabis plant without using sex-reversal techniques would be to use female individuals that naturally produce some male flowers under stress or spontaneously. However, this approach would apply selective pressure on plants that are more prone to showing hermaphroditic traits under stress, which is undesirable in cannabis breeding.

Modern sex-reversal techniques allow breeders to eliminate any plants that show hermaphroditic tendencies under stress from their breeding projects for improvement of feminized strains, no matter how exceptional the clone may be. The goal is to produce 100% female strains, which requires selecting elite clones through clonal selection. These elite plants must have little to no tendency to produce male flowers under stress and are referred to as “pure females.”

This approach enables cannabis breeders to explore new avenues in strain improvement through self-pollination and other techniques that involve self-pollination, such as "recurrent selection." Now, it is possible to apply these techniques without perpetuating hermaphroditic genes, applying selective pressure on desirable traits while excluding genes that promote hermaphroditism in each generation of the genetic pool. This pursuit aims to achieve what is commonly known in the cannabis world as pure females.

The notation for self-pollinations uses the letter "S" (from the English "selfing"). For this reason, S1 denotes the first filial generation of a self-pollination.

Mass Selection and Its Variants: This technique involves selecting individuals that display the desired traits and excluding those with undesirable characteristics. The crossbreeding of these selected individuals will produce the seeds used for planting the next generation. This process is repeated until a population that combines the sought-after traits is achieved. This technique has numerous variants and is often used in conjunction with other techniques in breeding programs.

Synthetic Varieties: Synthetic Varieties are populations created through the crossbreeding of several different genetic lines in open pollination, carried out in a balanced and isolated manner. The subsequent generations are then multiplied under the same balanced and isolated conditions. One result of this technique is our all-time classic and highly appreciated Cream Caramel® (SWS04).

Synthetic Varieties share with hybrid varieties the goal of taking advantage of the hybrid vigor and providing uniformity in the offspring. Additionally, through selection over successive generations, the most desirable characteristics are fixed in the population.

To develop this genetic line, we used a classic breeding method applicable to allogamous or partially allogamous species, such as cannabis. These types of cultivars are referred to in genetic terminology as Synthetic Varieties (S.V.).

Cream Caramel® (SWS04) is the result of the balanced combination of several of our best Indicas, chosen for their excellent agronomic, botanical, and chemotypic qualities, such as production, type and intensity of aromas, type and intensity of effects, plant structure, short flowering periods, trichome density, resistance to diseases, negligible tendency to hermaphroditism, and above all, their strong aptitude for producing outstanding hybrids.

To create our Cream Caramel®, we used three foundational lines: a Blue Black hybrid (Blueberry '99 x Black Domina '98) developed by the Sweet Seeds®’ R&D department, an outstanding Maple Leaf Indica with wonderful Afghan genetics, and a White Rhino that represents the most Indica-leaning and medicinal side of this renowned Dutch polyhybrid. Using these three parental lines, we created a balanced population consisting of an equal number of individuals from each parental line. These groups of plants were isolated into three different spaces to avoid self-pollination and to promote cross-pollination, maximizing heterosis or hybrid vigor. Thus, each line was allowed to intercross only with the other two parental lines.

The seeds from this first generation were harvested and mixed in equal numbers from the three pollination chambers, forming what we will call the SV1 generation, which contains all possible hybrid combinations of the foundational lines.

This SV1 generation was then allowed to freely cross-pollinate within isolation to prevent the introduction of foreign pollen, leading to crosses in all directions of all possible hybrid combinations (SV2). In this second generation (SV2), the seeds were formed from the random combination of gametes from all three parental lines. This population is panmictic, in equilibrium, and all subsequent generations will be identical to it under free pollination and no selection, as gene frequencies remain constant.

For the following generations, up to SV5, we applied "Mass Selection" by choosing a sufficiently large number of parental plants that displayed agronomic traits of interest to form the next generation, instead of leaving the process entirely to chance.

Cream Caramel® is a S.V. that, like hybrid strains, aims to improve hybrid vigor and provide uniformity to the offspring, while also fixing the most desirable traits through selection in successive generations. After five generations of free pollination and selection, the result is Cream Caramel®: a highly stable and productive strain with intense flavor and abundant resin. It is highly adaptable to unfavorable conditions and environmental challenges (cold, drought, etc.) due to its broad genetic bandwidth, which gives Cream Caramel® exceptional flexibility to adapt to its environment, even greater than that of F1 Hybrids.

To produce Cream Caramel®, as with all photoperiod-dependent cannabis seeds from Sweet Seeds®, we did not use males for pollination. Instead, modern sex reversal techniques were applied to selected female plants, resulting in a Synthetic Variety with approximately 99.9% female offspring.