Equatorial cannabis varieties

Cannabis is known to be a photoperiod-dependent plant; when day length decreases as summer draws to a close, the plants typically stop growing new shoots and leaves and begin to focus all of their energy on flower production. But at the equator, day length is consistently around 12/12, with very little seasonal variation.

High adaptability of cannabis

While cannabis is believed to have originated in east-central Asia, it has spread throughout the globe and established populations in an extremely wide and diverse set of habitats. Due to its exceptionally high level of phenotypic plasticity, the rate at which it has adapted to its adopted habitats is remarkable, and the number of known morphological and behavioural variations seems almost endless.

Cannabis is not indigenous to the equatorial regions, but it has spread through the tropical zones through natural means (and assisted by human activity), and equatorial populations have become established in various locations. These populations generally share several features in common, such as loose branches and airy flower structure, which increase airflow in humid environments and protect against mould. Equatorial plants typically take an exceptionally long time to flower, and so take full advantage of the year-long growing season; some specimens may flower for almost six full months and reach giant proportions.

In most equatorial regions, cannabis can germinate at almost any point in the year, and can grow almost all year round. In those regions that have a defined wet-dry seasonal variation, there are clear seasonal cues that the plant may use to trigger flowering. But even in regions with very little seasonal fluctuation at all, cannabis and many other plants seem to follow seasonal cycles, with flowering beginning and ending at roughly the same time each year.

Synchronisation of flowering

The signalling system whereby a plant sends the message to its various parts that it is time to commence flowering is highly complex and varies greatly between plants species. Our understanding of these processes is in its infancy, and equatorial plants are among the most puzzling of all.

For many plant species, achieving the correct timing for commencement of flowering is crucial. For optimum results, individuals in a species generally need to flower at around the same time so that the chance of successful cross-pollination is maximised. In areas with clear environmental triggers, such as a significant drop in day length or temperature, plants have evolved to sense these changes occurring and react accordingly. But for areas with very little variation in climate or day length, a more complex mechanism appears to be at work.

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Tropical species and circadian cycles

Many tropical rainforest tree species exhibit a similar mechanism. 30-65% of tropical tree species are so sparsely distributed that their population densities may be less than one individual per hectare, so synchronising the flowering stage is of the utmost importance if reproduction is to occur. Despite the lack of seasonal variation, these species exhibit timed responses including synchronous, bimodal (with two distinct ‘peaks’ per year), and staggered flowering, suggesting that a more subtle set of triggers enable this response.

It is unlikely that the age of the plant alone can determine this response, particularly for perennial trees that cycle between vegetative and reproductive growth. If age alone is the factor determining the beginning of the flowering phase, some other mechanism must at least control the cessation of flowering and the recommence of vegetative growth which occurs on an annual basis. Thus, subtle environmental variations must aid the plant in determining the correct time to flower, such as differences in the exact time of daybreak that would be entirely imperceptible to humans.

Photoperiod at the equator

While the overall change in day length remains fairly consistent throughout the year at the equator, there is some degree of seasonal variation. Due to the elliptical shape of the Earth’s orbit around the sun, the equator receives a total day length that varies by around 86 milliseconds per year, with the longest day falling on around July 2nd, when the planet is at the aphelion (the furthest point from the sun). While this is an infinitesimally short time, it may have a part to play—after all, even a brief flash of light mere seconds in duration can disrupt a cannabis plant’s growth during the dark period of the flower cycle, indicating that light-sensitivity mechanisms are very finely-tuned.

Further, it may be that the slight variation in light intensity and temperature caused by this phenomenon is also discernable by the plant. The planet is closest to the sun (at the perihelion) on around January 2nd, which partly explains why summers in the southern hemisphere are warmer—and also shorter, as the Earth orbits faster around the sun the closer it is to it.

As well as the Earth’s elliptical orbit, there are several other factors that add up to produce slight periodic (although not annual) day length variation at the equator. These include polar motion (where the rotational axis through the poles changes slightly, over a roughly seven-year cycle, meaning that the equator’s actual location varies correspondingly) and precession (long-term orbital cycles determined by external gravitational forces). As well as these, atmospheric refraction at the equator causes the sun to be visible in the sky after it has actually set, giving a day length or 6-8 minutes longer than night length. Atmospheric refraction may also fluctuate seasonally, depending on location and climate type.

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Day length variation in the tropics

Of course, all this adds up to mean that at the exact line of the equator itself, there is almost no seasonal variation in daylight hours. But even at 1° north or south of the equator (a distance of approximately 112km), there will be greater seasonal variation (approximately seven minutes’ difference) due to axial tilt. At 2°, there is up to thirteen minutes’ difference, and at 3° up to twenty; at the edge of the Tropics (around 23.5° N/S), there is just less than three hours’ difference. Thus, even for locations described as equatorial, there may be significant day length variation.

In practical usage, the terms ‘equatorial’ and ‘tropical’ are often used interchangeably; some would consider the entire tropical region up to the Tropics of Cancer and Capricorn to be equatorial regions. Others define the equatorial regions as occupying the latitudes from 0° to 5-10° N/S. Whichever definition is used, it is clear that plants habituated to the dramatic seasonal changes found in the temperate zones will be unsuited to this climate range, and that plants with a different set of flowering triggers would naturally become predominant in these areas once the mutations arose.

Other seasonal environmental variables

The equator is mainly comprised of tropical rainforest, which has a consistently hot, rainy and humid climate. Tropical savannah zones, with a pronounced dry season, and tropical monsoon zones, with a pronounced wet season, may also be found in certain equatorial regions. Monsoon zones are found close to the ocean and savannah zones are generally found in areas of higher altitude, such as the mountains of Kenya and Uganda. High elevation areas near the equator such as the mountains of Rwanda actually experience temperate climates year-round, although with heavy rainfall every day and very little seasonal variation in day length (although some variation does occur as the country is situated 2° south of the equator).

Equatorial regions that have naturalised populations of landrace cannabis include Ecuador, Colombia, Brazil, Equatorial Guinea, Kenya, Uganda, and Somalia. Other near-equatorial countries that have established populations of cannabis with similar growth characteristics include Mexico, Panama, Jamaica, India, Thailand, and Cambodia, among many others.

Evolution of equatorial cannabis strains

It is likely that a similar set of genetic mechanisms to those found in rainforest tree species exist in equatorial cannabis varieties. As cannabis is an annual plant that relies on pollination to reproduce (rather than vegetative propagation as many tropical plants rely on), its chances are improved if flowering can occur simultaneously with other individuals in the surrounding area.

The current (albeit shaky) consensus on the evolutionary origins of cannabis puts its origin in Kazakhstan and the surrounding areas of Eastern Europe and East-Central Asia—regions that undoubtedly experience a high level of seasonal fluctuation in daylight. As it spread to other climate zones from this area, it is likely that cannabis was originally photoperiod-dependent and that mutations arose in some populations that later became established.

Equatorial cannabis typically begins its life cycle earlier in the year than temperate varieties, and may grow for months before they begin to flower. They usually continue to put out new vegetative growth for weeks or even months after flowers have begun to emerge, which leads to the flower clusters taking on a slim, elongated appearance as the branch they grow on continues to lengthen. Conversely, temperate varieties undergo a more abrupt shift from vegetative to reproductive growth: once the branches have stopped growing, tight flower clusters begin to form at the existing internodes and terminal branches, and achieve great mass and density as branches cannot grow longer to accommodate them.

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Flowering triggers in equatorial cannabis

This system is controlled by a specific set of genes that, in temperate varieties, sends a hormonal signal from the leaf to the meristem (where new cells differentiate to ultimately become stems, leaves, flowers and so on) when light levels become consistently low enough to indicate that summer is drawing to an end. Conversely, in autoflowering plants, this mechanism is controlled by a different set of genes that signal the plant to cease vegetative growth and begin flowering once a certain number of internodes and branch sites have been produced.

Equatorial plants could be defined as autoflowering to some extent, as they will produce flowers after several months of vegetative growth without the need for a change in light cycles, but they clearly do not follow the same mechanism as the true autoflowering cannabis, C. ruderalis, if for no other reason than the gene signalling the end of vegetative growth once just 5-7 internodes have developed does not appear to be present (although it may be expressed later in the plant’s life), and its presence is not the key factor triggering flowering.

Are equatorial plants day-neutral or photoperiod-dependent?

Cannabis clearly has the potential to express short-day and day-neutral phenotypes, and there are several examples in nature of other plant species which express either phenotype in certain circumstances. More importantly, there are several examples of phenotypes that fall somewhere between the two extremes; it is likely that equatorial cannabis strains are another example of this phenomenon.

Studies into the model plant species Arabidopsis thalania are an important clue into the complexity of the genetic responses controlling triggering of flowering in plants. A. thalania is a long-day plant in normal conditions, but will eventually flower if only exposed to short-day conditions for a prolonged period. It is thought that one set of genes controls the response to day length, while other genes, involved in circadian rhythm, growth regulation and temperature response, also have a role to play in triggering flowering. In some mutations, the genes concerned with day length are inactive or under-expressed, and the plant falls back on other genes to determine its flowering pattern.

In autoflowering and temperate photoperiod plants, growth regulator genes express and switch off vegetative growth once flowering begins to occur. In equatorial cannabis varieties, it appears that these genes are not expressed in response to flowering occurring. This phenomenon causes equatorial varieties to produce flowers at the widely-spaced internodes, which then expand along the branch as it continues to lengthen, ultimately producing long, thin, airy flowers—unlike temperate strains, which produce dense flowers that cluster at the tightly-spaced internodes and terminal branches, which have ceased to lengthen by this point. However, the genes that control triggering and completion of flowering have not been identified.

It may be that cannabis has simply not fully adapted to equatorial conditions and still defaults to photoperiodicity if conditions allow; this would explain why many cannabis strains from the region do seem to respond to even minor fluctuations in daylight.

Other factors influencing flowering in equatorials

Many growers believe that equatorial cannabis begins to flower once its access to water or nutrients has been restricted. However if this were the case, equatorial plants would continue to grow and flower indefinitely if unrestricted, whereas they appear to still follow an annual life cycle. There are some reports of equatorial and near-equatorial cannabis surviving for two years, and producing a harvest for each growing season, but it is not clear if such specimens exist in the wild or if they are coaxed to do so by manipulating their environment. In areas with seasonal variation in rainfall, for example a wet-dry cycle, some plants may respond to restrictions in water that recur annually.

Breeding true perennial cannabis varieties would be an interesting area of research, as perennials have multiple advantages over annuals in terms of ecology and sustainability. As the vast majority of plants in tropical and equatorial regions are perennials (indeed, over 90% of plants species are perennials, with annuals generally being far more common in temperate latitudes), equatorial cannabis strains, which have begun to evolved more perennial-like characteristics, may be a good starting point for such research.

Cultivating equatorial cannabis strains

Overall it seems that the true equatorial sativas probably have enough seasonal cues to flower at the optimum time and synchronise flowering with other individuals nearby. It is possible that the genes that control this mechanism work in conjunction with genes determining overall age of the plant and that flowering is triggered by a combination of these factors, depending on location.

It is somewhat ironic to note that while equatorial cannabis strains have been the basis for some of the most famed hybrids developed for the seed market, equatorial growers often find themselves struggling to find appropriate genetics as very few pure strains are commercially available. The characteristic growth patterns, huge proportions and exceptionally long flowering time are undesirable traits for indoor cultivation, so most hybrids have attempted to diminish these traits and retain just flavour and potency.

Multiple growers around the equator have attempted to grow strains that have been adapted for indoor cultivation or for more northerly latitudes, and have encountered various problems. The many problems reported include total failure to flower, plants switching back and forth between vegetative and reproductive growth, copious mould, and extremely low yields.

How to get the most out of equatorial cannabis strains

Growers lucky enough to have access to local landrace genetics and located at or near the equator need to do little more than ensure their plants are given adequate access to sunlight, water and good soil. Depending on the strain, flowering may begin after just a few weeks of vegetative growth, while others may grow for three or four months before flowering.

The flowering stage may then last as long as six months; some growers report flowering occurring practically all year round. In areas with monsoon climate, starting seeds at the end of the wet season and allowing them to grow through the drier seasons is generally advisable, and in the savannah zones, seeds should be started towards the end of the dry season.

Pure equatorial strains are difficult to grow outdoors in the temperate zones, and are generally considered unsuitable for indoor cultivation due to their gigantic proportions and long flowering time. However, if attempting to grow equatorial strains indoors, providing a 13/11 lighting cycle during vegetative growth and an 11/13 cycle during flowering is generally considered to yield better results. Plants can be trained and topped repeatedly to limit vertical growth, and products known as vertical growth regulators can also be employed if necessary.