by Seshata on 05/08/2014 | Cultivation

All about autoflowering cannabis

Automatics Autoflowering cannabis varieties have been steadily gaining in popularity over the last five years or so, as improved breeding techniques have created new and better strains. Now, it is possible to grow abundant, high-potency harvests in as little as nine or ten weeks, from germination to harvest.

Autoflowering cannabis in botany

Autoflowering cannabis is descended from wild Cannabis ruderalis populations found in Eastern Europe, Russia, China and elsewhere in central and northern Asia. As with other species and subspecies within the Cannabis genus, the botanical classification of C. ruderalis is disputed. Some botanists classify it as a species in its own right, others that it is a subspecies of C. indica or C. sativa.

In 2003, chemotaxic and genetic analysis of cannabinoid variation in 157 varieties of cannabis indicated that C. sativa and C. indica were two separate species, and that C. ruderalis is a subspecies of C. sativa. However, even this is disputed. In 2005, new analysis revealed that C. ruderalis may indeed be a species in its own right, and a ‘sister’ species to C. indica and C. sativa. It appears that C. ruderalis species are always found at 50°N of the equator or even higher latitudes.

Autoflowering cannabis varieties are now far more potent than their predecessors
Autoflowering cannabis varieties are now far more potent than their predecessors

The analysis also indicated that C. sativa comprises non-drug varieties of feral cannabis and cannabis grown for fibre and seed (i.e. hemp) that are typically common to Europe and east-central Asia.

On the other hand, C. indica is found in the south and east of Asia and comprises all drug varieties, both narrow and wide-leaved, as well as some fibre and seed varieties and some feral Himalayan populations (which may or may not have high cannabinoid content).

Autoflowering cannabis and day length

What the specifics of the classification, what defines autoflowering cannabis or C. ruderalis is its growth characteristics.

Unlike most varieties of cannabis (which are classed as photoperiod-dependent or short-day plants), C. ruderalis is not dependent on seasonal changes in daylight to commence flowering; instead, it flowers according to the age of the plant.

It is believed that positive selection pressures enabled this spontaneous mutation to become established in several independent escaped populations, rather than that all autoflowering cannabis varieties descended from a single specimen.

Crystal coverage on an autoflowering White Diesel Haze
Crystal coverage on an autoflowering White Diesel Haze BUY WHITE DIESEL HAZE HERE >>

Most cannabis varieties in their natural habitat germinate in early spring; in the northern hemisphere, this may occur as early as February or as late as April or May, depending on climate.

They then enjoy as much as six months’ of vegetative growth before the hours of daylight drop, and commence flowering in late August or September, close to the autumnal equinox. They may continue to flower until December, if temperatures allow, or may be ready to harvest by as early as mid-October.

Positive selection of autoflowering traits

In the cold north, the rapid reduction in daylight hours as winter approaches, along with the rapidly decreasing temperatures and overall short growing season, means that cannabis plants do not have the luxury to grow for such a large proportion of the year.

Instead, they must complete vegetative growth quickly as they do not typically appear until mid-May or June, when frosts thaw completely, and they must produce flowers quickly before frosts set in again, which may be as early as September.

Thus, wild or escaped cannabis populations in such areas began to positively select for plants that could withstand the harsh environmental conditions. Reduced cannabinoid content, shorter stature, and ability to autoflower are all positive traits in such an environment, and so when such mutations arose, their offspring were more successful than others and the traits became established over time.

C. ruderalis is a short-statured plant, rarely exceeding 90cm in height and more commonly reaching 40-50cm; it has few side branches, and produces small flowers. The leaves may be wide-leaved or narrow-leaved, but are more commonly narrow. C. ruderalis varieties typically begin flowering after just two or three weeks following germination.

From germination to harvest, ruderalis plants typically take around ten weeks, but some varieties are ready in as little as six and a half weeks. Plants are usually highly resistant to frost, pests and diseases, and can be grown with relatively little nutrient supplementation even in poor soil.

The genetics controlling autoflowering characteristics

For a plant to successfully reproduce the timing of the transition to flowering is crucial; in most plant species, the most important factor determining the timing of the transition is variation in photoperiod.

The specific gene or genes controlling photoperiod dependency or lack thereof has not been identified in cannabis, although there have been various attempts to determine the genes responsible for similar mutations in other plant species, which may help to shed light on the mechanism at work in the cannabis plant.

Autoflowering cannabis strains typically grow to heights of around 40-50cm
Autoflowering cannabis strains typically grow to heights of around 40-50cm

Plants rely on specialised proteins known as photoreceptors to sense subtle changes in light duration and intensity. These proteins fall into four main categories: phytochromes, which sense red and far-red wavelengths; cryptochromes, which sense blue wavelengths; phytotropins, which control growth and movement in response to light (such as flowers following the daily path of the sun in the sky), and UVR8, which responds to UV-B light.

In photoperiod plants, these photoreceptors are responsible for transmitting flowering when daylight hours reach a critical threshold. For short-day plants like cannabis, this threshold is reached after a period of gradual reduction in daylight hours; in long-day plants, after a gradual increase. Autoflowering plants are considered day-neutral, in that flowering is triggered via independent mechanisms and not in response to day-length variation.

While the genes controlling the process are still undetermined, previous research on other plant species has postulated that a speculative signalling hormone known as ‘florigen’ is transmitted from the photoreceptors to the shoot apex (the part of the plant that controls new growth) when it is time to commence flowering. However, it is not known exactly what florigen is, and how the process differs between photoperiod-dependent and autoflowering plants.

Florigen and photoperiod plants

In Arabidopsis thalania, a small, long-day plant in the Brassicaceae family that is often used for in genetic research as it was the first to have its genome fully sequenced, it appears that circadian regulation of the expression of a gene known as CONSTANS (CO) may have a role to play. As expression of CO increases, it causes expression of another gene known as FLOWERING LOCUS T (FT), which is believed to be a major component of the elusive florigen hormone.

The mechanism behind this is arrestingly neat. The phytoreceptors trigger the production of messenger RNA (mRNA) that translates to CO protein every day approximately twelve hours after daybreak; however, CO protein is only stable in daylight, and breaks down rapidly in low light conditions. Thus, the levels of CO protein required to trigger production of FT are only achieved on days that are substantially longer than twelve hours; thus, when spring takes hold and day length increases, flowering can commence.

Florigen and day-neutral plants

While it is believed that the CO gene is crucial to triggering flowering in long-day and short-day plants, it is clear that a different mechanism must be at work in autoflowering (also known as day-neutral) plants. Studies into day-neutral tomato varieties indicate that a gene known as SINGLE FLOWER TRUSS (SFT) triggers production of FT, potentially in tandem with the SELF PRUNING (SP) gene.

The SFT and SP genes are involved with regulation of stem and shoot growth, signalling the plant to cease vegetative growth when a full set has been generated; when this occurs, the FT gene is triggered.

Super autos grow to around 90cm, and take longer to flower, but produce abundant harvests
Super autos grow to around 90cm, and take longer to flower, but produce abundant harvests

Many plant species have now been researched in order to investigate the genetic changes at work in mutations that affect photoperiod sensitivity. Various different pathways have been described, mostly involving a complex combination of different genes; however, there appears to be no research that is cannabis-specific.

Breeding C. ruderalis to create commercial strains

As C. ruderalis does not produce high levels of cannabinoids, it was overlooked by breeders of drug cannabis varieties up until just a few years ago. The details of the original breeding programs are shrouded in secrecy, but it appears that the LowRyder, bred by the Joint Doctor, was the first commercially-available variety.

According to industry legend, the LowRyder descended from a mysterious strain known as Mexican Rudy, believed to be a cross between Mexican sativa and Russian ruderalis, a short, fast-flowering strain with low cannabinoid levels and a nondescript flavour.

Autoflowering cannabis does not respond to changes in photoperiod but flowers according to age
Autoflowering cannabis does not respond to changes in photoperiod but flowers according to age

The Mexican Rudy was crossed with a Northern Lights female; the female offspring was then crossed with William’s Wonder. The offspring were then selected for particularly short and fast-flowering traits, and back-crossed until the autoflowering and short-stature characteristics were consistently present in all individuals.

The LowRyder was made commercially available shortly after this, although reactions to it were mixed, with some praising its potential and others criticising its poor taste and potency.

Alternatively, some speculate that the LowRyder was developed from a Finnish strain of autoflowering hemp known as Finola. Whatever the origin of the LowRyder, it is certainly the basis for many of the subsequent crosses that have been created in recent years, many of which have far surpassed initial levels of potency and flavour and are of far greater interest to growers and smokers alike.

Indeed, the Joint Doctor’s next foray into autoflowering strains brought the community the LowRyder #2, which was crossed with Brazilian Santa Maria and boasted greatly improved taste and potency.

What are super autos?

It has been possible to cross ruderalis strains multiple times with photoperiod-dependent plants and retain the autoflowering characteristic. After the offspring are bred several times with photoperiod plants, the percentage of ruderalis genetics is reduced, and undesirable characteristics such as low yield and uninteresting flavour and potency can be bred out.

It is thought that in super autos, the gene that signals the end of vegetative growth and the beginning of the flowering period kicks in later, allowing the plant to reach far greater height and circumference. The result is taller plants which take longer to grow, but still begin automatically flowering, and produce improved yields.

Short stature and minimal branching allows autoflowers to be easily concealed among other plants
Short stature and minimal branching allows autoflowers to be easily concealed among other plants

Many existing super auto strains were apparently developed by a breeder known as Stitch, who claims that his varieties contain no ruderalis but are in fact simply photoperiod-dependent plants that have been selected to finish early.

However, as most reports suggest that they flower even in consistently long day length, it is likely that they do in fact contain ruderalis but are being misrepresented due to entrenched distrust of ruderalis genetics still displayed by many members of the growing community.

Super autos commonly grow for longer than fourteen weeks, with the longest-flowering super auto hazes taking up to eighteen weeks from start to finish (for comparison, the longest-flowering non-auto hazes may need eighteen weeks just to flower). Super autos often reach heights of around 90-100cm, and are capable of producing abundant, resinous flowers with excellent taste and potency.

Now, the better of the new-generation autos and super autos are actually being grown by outdoor growers in regions where photoperiod-dependent plants can grow; now that their flavour and potency rivals their non-auto peers, their advantages of rapid growth, short stature and hardiness are rendering them increasingly attractive even to the most discerning of growers.

How to get the most out of autoflowers

  • Outdoors, autoflowering cannabis varieties generally require very little care. They can flourish in poor soil with low temperature and precipitation levels, and require little extra feeding to produce their harvest. Often, they can be germinated outside and left all but unattended until they are ready for harvest, although some preventative measures may need to be taken against pests, such as slug pellets or chicken wire to keep out rabbits and deer.
  • Indoors, most growers tend to keep their autoflowering cannabis strains on a permanent 18/6 lighting cycle, with some favouring a 14/10 cycle. Others give the plants up to 24 hours of daylight, although it is often said that exceeding 20 hours of daylight leads to diminishing returns. The plants prefer airy, low-nutrient soil, so opting for a light mix from a grow supply store is appropriate.

The plants require little feeding. During vegetative growth, the plants may only need to be fed once or twice with suitable growth-phase nutrients. Flower-phase feeding should always cease at least one week prior to harvest, and the plants should be fed pure water so that they can be flushed of nutrient build-up.

Autoflowering cannabis and daylight spectrum

Although autoflowering plants do not depend on changes in photoperiod to provide the stimulus to begin flowering, there is some anecdotal evidence that lighting variations can affect their growth.

According to some reports, using blue-spectrum during the vegetative stage allows for more vigorous growth, and shifting from blue light to red light when flowering commences allows the plant to begin flowering at an accelerated pace and achieve overall higher yields.

This excellent specimen is almost ready for harvest
This White Diesel Haze is almost ready for harvest BUY WHITE DIESEL HAZE HERE>>

There may also be scope for further investigation into diurnal variations in light and their effect on the growth pattern of cannabis plants, particularly autoflowering varieties.

It has been noted that flowering trigger signals work in conjunction with plants’ circadian rhythms; it is also known that daylight varies predictably according to the hour and the angle of the sun’s rays hitting the earth to produce blue-spectrum light in the morning and red-spectrum light at night-time.

Very little research has been done into the effects of diurnal spectral variation in cannabis, and it may prove to be a worthy topic for future investigation.

Comment Section

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Very interesting article! thanks





Scarlet Palmer

Hi Jo Ann,

Sensi Seeds provide a range of autoflowering seeds, which you can find here.

Thanks for your interest!


Ben Weatherstaff

I must read everything you have written! I just came across your blog while searching fro something on Robert Connell Clarke to add to my fledgling site on medicinal cannabis. I feel fortunate to have discovered you. does Sensi have autoflowering stabilized CBD rich strains, or do they even exist?



Hi! Thx!
According to grow in the same way they are for example also in 12/12 lighting conditions? the same amount?



I have been searching for information to get an Auto back into Veg and find very little to nothing. Maybe light spectrum has more to do with it because under MH is was not flowering. But I switched to HPS and they flowered , I am sad because I really did not want them to flower.



Can you use 247 light cycle from start to finish. Using CFL 2700k.


Scarlet Palmer

Hello Teejay,

Thank you for your comment ? Unfortunately we cannot respond to grow questions on the blog, but we do have the Sensi Seeds Forum where you can ask a thriving community of gardening fans for advice, share your experiences, and see if your question has already been covered. I hope this helps.

With best wishes



Daniel Mcdougall

Do you veg with blue or red cfl,also mars dual veg,bloom,i have 6" with red cfl.....put it under 600 red in 3 weeks?never tried auto,s.any advice.


Scarlet Palmer

Hi Daniel,

Unfortunately, legal restrictions prevent us from answering grow-related questions on the blog. You could have a look at the Sensi Seeds Forum, where there are extensive threads on many aspects of cultivation and it is possible that a similar question to yours has been discussed. Sorry I can't help you further!

With best wishes,



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