CANNABIS GROWING
From ruderalis genetics to nutrient schedules and seed selection: everything growers need to successfully cultivate autoflowering cannabis from seed to harvest in 60–90 days.
Autoflowering cannabis strains flower based on age rather than changes in the light cycle. Standard photoperiod cannabis plants wait for a signal — a shift to 12 hours of darkness per day — before initiating the flowering stage. Autoflowers ignore this signal entirely. They begin flowering after a genetically programmed vegetative period of 3 to 5 weeks, regardless of whether they are under 18, 20, or 24 hours of daily light.
This trait originates from Cannabis ruderalis, a subspecies of cannabis that evolved in the short-summer environments of Siberia, Russia, Mongolia, and Central Asia. In these regions, summer days are extremely long but brief. A plant that waited for short days to flower would never complete its life cycle before the cold killed it. Ruderalis solved this by evolving to flower on an internal timer, ensuring seed production every season regardless of photoperiod.
In photoperiod cannabis, flowering is controlled by the interaction of the plant’s circadian clock with light-sensing phytochromes and cryptochromes. Extended periods of darkness reduce the activity of flowering repressors, allowing the florigen signal (likely FT-like proteins) to travel from leaves to the shoot apex and trigger flower initiation. Breeding studies and QTL mapping have identified the autoflowering locus in ruderalis as a recessive allele that effectively decouples flowering from phytochrome signalling. The circadian clock in autoflowers continues to function, but the downstream photoperiod pathway that normally gates flowering is non-functional.
In practical terms: autoflower plants monitor their own chronological age. The vegetative-to-flowering transition is initiated after the plant has accumulated sufficient biomass (typically 3 to 5 weeks from germination) regardless of the light environment. This is why autoflowers cannot be kept in permanent vegetative state by simply extending the light period — flowering will begin on schedule regardless.
| Factor | Autoflower | Photoperiod | Notes |
|---|---|---|---|
| Light schedule | 18/6 or 20/4 throughout | 18/6 veg → 12/12 flower | Autos: no light change needed |
| Seed to harvest | 60–90 days | 90–150+ days | Autos: up to 3 harvests per year indoors |
| Plant height | 40–100 cm | 60–300 cm | Autos suited for stealth and low tents |
| Yield per plant | 50–150 g | 100–500+ g | Photoperiod higher per plant; autos compensate via multiple runs |
| THC potential | 16–26% (modern) | 15–33% | Gap narrowed in 3rd-gen auto genetics |
| Difficulty | Beginner-friendly (no timing) | More control; higher ceiling | Autos less forgiving of early errors |
| Cloning | Not practical | Full cloning capability | Autos require fresh seeds each run |
| Outdoor season | Any season (60–90 days) | Determined by latitude/season | Autos: multiple outdoor harvests per season |
| Strain | Days (Seed to Harvest) | THC | Yield (Indoor) | Notes |
|---|---|---|---|---|
| Quick One (RQS) | 55–65 days | 13% | 40–75 g/plant | Fastest commercially available auto |
| Auto Blueberry (Dutch Passion) | 60–70 days | 16% | 50–100 g/plant | Berry aroma; beginner-friendly |
| Northern Light Auto (RQS) | 65–75 days | 14% | 50–100 g/plant | Classic indica effects; reliable genetics |
| Auto AK-47 (Serious Seeds) | 65–75 days | 18% | 75–120 g/plant | Balanced hybrid effects; easy grow |
| Gorilla Glue Auto (FAST Buds) | 70–80 days | 24% | 400–600 g/m² | High-potency auto; heavy resin |
| Wedding Cake Auto (FAST Buds) | 75–85 days | 25% | 450–650 g/m² | Premium auto; not for beginners |
| Zkittlez Auto (Barney’s Farm) | 70–75 days | 22% | 350–500 g/m² | Fruity indica profile; compact |
| Sour Diesel Auto (FAST Buds) | 70–80 days | 22% | 400–600 g/m² | Sativa-dominant; creative, energetic |
The most practical aspect of autoflower cultivation is the removal of light-cycle management from the grower’s responsibilities. Photoperiod grows require a deliberate switch from 18 hours to 12 hours of light to trigger flowering — a mistake at this stage can delay harvest by weeks or cause hermaphroditism. Autoflowers simply need consistent light from start to finish.
The recommended light schedule for autoflowers is 18 to 20 hours of light per day. This provides sufficient photosynthesis time without the added electricity cost of 24-hour light. The 4 to 6 hours of darkness, while not required for flowering, allows the plant’s enzymatic processes to operate in a natural dark-phase rest cycle, which many experienced growers associate with stronger terpene and resin development.
Autoflowers should be sown directly into their final container. Transplanting during autoflower cultivation causes transplant shock that consumes days the plant cannot recover from — the timer does not stop while the plant recovers. A 10–15 litre fabric pot is the standard final container for a single autoflower indoors. Fabric pots promote air-pruning of roots, prevent overwatering, and support lateral root development that maximises yield in the compact autoflower root zone.
| Characteristic | Cannabis ruderalis (wild) | Modern Auto Hybrid | Breeding Change |
|---|---|---|---|
| THC content | 1–3% | 16–26% | Photoperiod genetics backcrossed in |
| Height | 20–60 cm | 40–100 cm | Hybrid vigour from indica/sativa cross |
| Flowering trigger | Age (autoflowering) | Age (autoflowering) | Retained from ruderalis parent |
| Seed-to-harvest | 55–70 days | 60–90 days | Slightly longer due to photoperiod genetics |
| Origin region | Siberia, Russia, C. Asia, E. Europe | N/A (bred globally) | Commercialised from 1980s–2000s |
| Aroma/flavour | Minimal, low terpene | Complex (donor strain profile) | Terpene profile comes from photoperiod parent |
Autoflowers have a smaller root zone than photoperiod plants and a compressed life cycle that leaves no room for recovery from nutrient burn or lockout. The fundamental rule is feed less than you think you need to. Most nutrient-related autoflower failures come from overfeeding, not underfeeding.
Start nutrients at 25–50% of the manufacturer’s recommended dose and increase gradually only if the plant shows no signs of stress. Watch for the first signs of nitrogen toxicity — leaves curling downward at the tips (the “claw”) — and reduce feeding immediately if this appears.
| Growth Stage | Approx. Days | N:P:K Ratio | Nutrient Level | Key Notes |
|---|---|---|---|---|
| Seedling | Days 1–14 | No feeding | Water only (plain pH water) | Seed nutrients sufficient; pre-amended soil provides all needed |
| Early veg | Days 14–28 | 3:1:2 | 25% of full dose | Introduce nutes slowly; watch for clawing |
| Pre-flower / early flower | Days 28–45 | 1:3:2 | 50% of full dose | Transition: reduce N, increase P for bud development |
| Mid–late flower | Days 45–65 | 0:3:3 | 50–75% of full dose | PK boosters can be added; Cal/Mag if using RO water |
| Final 2 weeks | Days 65–harvest | Flush only | Plain pH water | Flush excess nutrients; improves flavour and burn quality |
Autoflowers are not the right choice for every grower, but they are the best choice for a specific set of situations:
Autoflowers are not ideal for growers who want to clone their best plants, who need maximum yield from a single plant, or who want to correct growing errors by extending the vegetative period. For those goals, photoperiod genetics remain superior.
The quality gap between autoflower seed banks is significant. Well-established breeders such as FAST Buds, Dutch Passion, Royal Queen Seeds, and Barney’s Farm have invested in stabilising their autoflower genetics across multiple backcross generations, resulting in consistent performance between plants. Lower-quality genetics from undisclosed breeders often produce inconsistent phenotypes, hermaphroditism under stress, and lower-than-advertised THC levels.
When evaluating autoflower genetics, look for: published third-party lab test results showing THC percentage, detailed seed-to-harvest timeline data from real grows, genetic stability notes showing at least F4 or BX3 generation, and a germination guarantee. Spending more on quality genetics pays dividends in a grow where there is no vegetative buffer period to compensate for variable plant quality.