Autoflowering Strains: Growing Without Light Cycles

Autoflowering strains have revolutionised cannabis cultivation. Instead of waiting for light signals, they automatically start flowering after a genetically fixed period – regardless of whether days are getting shorter. This makes them particularly interesting for beginners, outdoor growing, and scenarios where multiple harvests per year are planned.

## Cannabis Ruderalis: The Genetic Basis

The ability to flower automatically comes from Cannabis ruderalis, a subspecies from Central Asia and Siberia. Ruderalis plants had to survive in a climate with short summers and unpredictable day length – evolution's solution was to link flowering to the plant's age rather than light duration.

Modern autoflowering seed stock is the result of years of crosses between ruderalis and high-performing indica or sativa varieties. Early autos from the 2000s and early 2010s had low THC content and modest yields. Third and fourth generation varieties available today have largely closed this gap.

## Timeline: Seed to Harvest in 60–80 Days

The most important practical advantage of autoflowering strains is the short total duration. While photoperiodic strains take 3–4 months (veg + flower), an autoflowering strain typically completes its cycle in 60–80 days from seed to harvest.

Week 1–2: Germination and seedling stage. The root develops, first true leaves appear. A sensitive period – no overfeeding.

Week 3–4: Vegetative phase. The plant grows rapidly. First flower sites can become visible as early as week 3–4 without changing the light cycle.

Week 5–9: Flowering. The plant concentrates all energy on flower development. Trichome production increases, aroma intensifies.

Week 8–10: Harvest (strain-dependent). Trichome inspection, as with photoperiodic strains, determines the exact timing.

## Light Cycle: 18/6 or 20/4 as Standard

Since autoflowering strains don't need a 12/12 signal, the light cycle can be kept constant throughout the entire life cycle. Most growers choose between:

18 hours light / 6 hours dark: The most common setting. Good growth, moderate electricity costs, similar to a natural summer day.

20/4 or even 24/0: Autos can also grow under constant light. 20/4 is considered a good compromise between maximum light and a brief recovery period for the plant.

## Substrate and Nutrients: Lighter Than for Photoperiodics

Autoflowering plants are smaller and grow faster – meaning they need a lighter, less nutrient-rich substrate than their photoperiodic counterparts. Too many nutrients in early stages can inhibit development.

Recommended mix: 70% quality potting soil + 30% perlite. This ensures good drainage and sufficient oxygen at the root.

Nutrient dosing: Start at half the recommended dose and increase carefully as needed. Autos are more sensitive to overfeeding than large photoperiodics.

Pot size: 7–11 litres is sufficient for most autoflowering strains. Since autos should only be transplanted once (or ideally not at all), plant directly into the final pot.

## Yields and Quality: Caught Up, But Still Differences

Modern autoflowering strains can achieve 80–150 grams per plant under optimal conditions. High-performance strains like Wedding Cake Auto, Gorilla Glue Auto, or Bruce Banner Auto deliver results that compete with good photoperiodics.

THC content in premium autos today reaches 20–25%, occasionally higher. The terpene profile has also improved significantly. Nevertheless: under the same conditions, photoperiodics generally produce more total yield since they can be kept in the vegetative phase longer.

## Outdoors: Multiple Harvests in One Season

For outdoor growing, autoflowering strains are a special option. In Germany, the short cultivation period of 60–80 days theoretically allows up to two harvests between May and October – provided temperatures cooperate.

Practical outdoor schedule (Germany): - First sowing: mid-May (after last frosts) - First harvest: mid-July to early August - Second sowing: early July - Second harvest: mid-September

Outdoor growing of up to three female plants is permitted under the KCanG for adults – autoflowering strains are well-suited for this as no light management is needed.

## Common Mistakes with Autos

Transplanting: Autos operate on a fixed schedule. Any stress from transplanting costs development time that cannot be recovered. Sow or germinate directly in the final pot.

Too much fertiliser: Especially in the first three weeks. Autos generally start with what the substrate provides – external nutrient additions from week 3–4 at the earliest.

Too small a pot: Root restriction directly limits growth. Minimum 7 litres, for large strains 11–15 litres.

Too little light: Autos are not a miracle solution under poor light conditions. 400–600 µmol/m²/s PPFD is the minimum for decent results.