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Autoflowering cannabis varieties automatically switch from vegetative growth to the flowering stage with age, as opposed to the ratio of light to dark hours required with photoperiod dependent/short-day strains. Many autoflowers will be ready to harvest in less than 10 weeks from seed. Dwarf varieties can have short stature while still giving decent yield. Conversely "super autos" can take over 100 days to mature and can reach over 6 feet tall.
The origins of autoflowering cannabis are still debatable. The strain Lowryder by breeder The Joint Doctor was the original large scale marketed autoflower. Lowryder contains genetics from a Mexican strain that was referred to as Mexican Rudy and is believed to be created from a cross between a Mexican sativa and a Russian Cannabis ruderalis. Another theory is that the early genetics came from the first oilseed hemp variety called Finola, which was developed from Russian stock in Finland during 1995. These early hybrids with large amounts of C. ruderalis genes were lacking some of the finer qualities of high grade cannabis strains available.
Further hybrids from these ruderalis dominant strains were created using some of the more popular and standard photo-period sensitive strains. Since the first mass market autoflower, Lowryder, many improvements have been made by breeders. The genetics behind these new autoflowering strains that breeders are producing are generally not shared or if so only in very vague terms. This secrecy is done to keep others from producing knock offs of the strains, and more often, to obscure revealing that new strains are, more often than not, descended from the original Lowryder, which is often criticized as a substandard strain of low potency.
As of January 2012, online vendors offer nearly 200 autoflowering strains with Autoflowering Blueberry, Cream Caramel Auto, and Afghan Kush Ryder being the most sold varieties in the market.  Most of these strains can be identified by the presence of "ryder" (such as Afghan Kush Ryder by breeder World of Seeds) or "automatic" (or "auto" such as with the Auto Ak47 bred by Lowlife) in their names.
The newly produced strains of autoflowering cannabis have proven that they can produce quality medicine comparable with classical short-day strains. Breeders have reported THC content in the low 20% in some newer varieties while many varieties also have high CBD content. The advantages that autoflower breeders report with their plants include:
- Short life span with many going from seed to harvest in under 13 weeks (some as short as seven weeks)
- Can be kept short in stature for "stealth" growing
- The Cannabis ruderalis heritage causes flowering after 2–3 weeks from germination
- No need for a separate vegetative and flowering environment (unlike with photoperiod dependent/ short-day strains)
- Simple seed production, one plant can produce several hundred seeds even at 1 foot (30.5 cm) tall
- Due to short life span can be grown in cold climates where summers are short and cold
- Can be grown outside in city environment where there is artificial lighting, that would affect (stress) regular strains
- Can produce multiple harvests outdoors in one season
There continues to be some short-day cannabis growers that insist that autoflowers are simply a fad and produce subpar flowers. The number one reason for these feelings are the understandable disappointment many had with the results of the first Lowryder. Also commonly argued is that when growing indoors, growers already have the ability to initiate flowering with photoperiod/short-day plants at will by changing the lighting. Hormones such as BAP and paclobutrazol can also be used to completely arrest vertical growth in photoperiod plants. However, there are concerns about the carcinogenicity of some of these growth regulators. When growing outdoors, initiation of flowering in short-day plants is more difficult to control than with autoflowers. Another concern is the overall yield of autoflowering plants which with some dwarf strains can be a half ounce per plant.
The last concern with autoflowering cannabis is the chance of buying genetics that do not actually automatically flower regardless of photoperiod.
Most of the autoflowering seeds available in the market are feminised. Only a few brands do regular autoflowering seeds.
Creating true autoflowering seed from two quality, true breeding autoflowering parent plants is easy for most. Breeding new autoflowering strains becomes more difficult when attempting to make a hybrid with a non-autoflowering strain. Some photoperiod/short-day cannabis strains are heterogeneous - containing the recessive day-neutral or autoflowering genetics along with the dominant short-day genetics. However a proper list of such strains is not yet available so most breeders treat all short- day plants as homozygous dominant.
A true autoflower is homozygous recessive for the day neutral genetics. Therefore, most crosses between classical photoperiod/short-day strains and autoflowers produce few or no autoflower progeny in the F1 generation. Regardless of whether the F1 generation produces autoflowering plants, the higher performing and similar plants need to be recrossed. This F2 generation will contain approximately 25% of homozygous recessive plants which are autoflowering. Still the few autoflowers produced are not always stable and may require further stabilization. Further complexities with stabilizing autoflowers has previously led to non autoflowering and low quality strains making it into the market.
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