Black Jack Auto® Sweet Seeds – Fast 9-Week Autoflowering Strain with 19% THC

Black Jack Auto® by Sweet Seeds is a 3rd generation autoflowering strain that delivers premium, resin-rich buds in just 9 weeks from germination, making it a top choice for fast, high-impact harvests with minimal effort.

Are you tired of waiting months just to enjoy your own homegrown buds?

Most photoperiod strains keep you on hold for 12+ weeks before harvest. That’s a long time when you’re eager to taste fresh, aromatic flowers or need a reliable supply without delays.

What if your grow space is limited or your patience is running thin?

Long cycles mean more light, more nutrients, more risk of pests or mold. And if you’re growing discreetly, every extra week increases exposure. Plus, inconsistent results can leave you frustrated and empty-handed when you need it most.

Meet Black Jack Auto® — the 9-week powerhouse that delivers quality, speed, and consistency, all in one sativa-dominant autoflower.

Bred from Sweet Afgani Delicious Auto® and a Jack Herer elite clone, this strain hits fast and hard with 19% THC, dense trichome coverage, and a sweet-spicy aroma with earthy incense notes. Whether you're indoors or outdoors, it finishes in just 9 weeks with yields up to 550 g/m² (1.94 oz/ft²) and plants reaching 0.40–1.10 m (1.31–3.61 ft).

Less waiting, more winning: Why this strain dominates the autoflower game

Black Jack Auto® isn’t just fast — it’s smart breeding at its finest. It combines the resin production of Black Domina with the cerebral kick of Jack Herer, all wrapped in a compact, low-maintenance autoflower. No complex light schedules, no months of care — just plant, feed, and harvest top-shelf buds in record time.

What you gain with a 9-week grow cycle

• Harvest fresh buds in under 10 weeks — no more 3-month waits
• Grow multiple rounds per year, even in colder climates
• Reduce electricity and nutrient costs with shorter cycles
• Enjoy a clean, uplifting high without heavy sedation
• Get dense, resinous flowers that smell like sweet citrus and incense

How to grow Black Jack Auto® for maximum results

For a strong start, germinate seeds in a moist environment at 22–25 °C and high humidity. Use a light, well-aerated substrate like All Mix Peat Free by Bio Bizz to prevent overwatering and support root development. Transplant carefully once the taproot is about 1 cm (0.4 in) long.

During growth, maintain 18–20 hours of light daily — no changes needed. Keep temperatures between 22–26 °C and humidity at 50–60%. Avoid aggressive pruning; instead, use gentle LST to shape the plant early. For sustained vigor, Rhizotonic XP boosts root health and resilience.

In flowering, reduce humidity to 40–50% to prevent mold, especially with its dense buds. Feed with a balanced flowering fertilizer and consider adding Top Bud in the final weeks to enhance resin and bud density. Flush 7–10 days before harvest when 50–70% of trichomes turn amber for a smooth, balanced effect.

Technical specifications

• Breeder / Brand: Sweet Seeds
• Type: Autoflowering
• Dominance: Sativa-dominant hybrid (66.9% Sativa, 30% Indica, 3.1% Ruderalis)
• Genetics: S.A.D. Sweet Afgani Delicious Auto® × Jack Herer elite clone
• Life cycle: 9 weeks from germination to harvest
• Indoor yield: 400–550 g/m² (1.41–1.94 oz/ft²)
• Outdoor yield: 40–250 g/plant (1.41–8.82 oz/plant)
• Height: 0.40–1.10 m (1.31–3.61 ft)
• Difficulty: Low to medium
• Structure: Compact with strong branching and high vigour
• Climate: Thrives in temperate, Mediterranean, and continental climates; tolerates mild cold
• Resistance: Moderate resistance to mold and pests
• Training: Suitable for LST and low-stress techniques; avoid topping or FIM
• Pot size: 18–27 L final pot recommended
• Light cycle: 18–20 h daily throughout
• Temperature: 22–26 °C (veg), 20–25 °C (flowering)
• Humidity: 60–70% (seedling), 50–60% (veg), 40–50% (flowering)
• pH: 6.0–6.5 (soil), 5.8–6.2 (coco/hydro)
• Smell during grow: Medium to high — consider a carbon filter
• THC: 19%
• CBD: 1.1%
• Aromatic profile: Limonene, myrcene, pinene
• Flavour: Sweet, sour, spicy, incense
• Effect: Uplifting, creative, stimulating — ideal for daytime use

Frequently Asked Questions

Can I grow Black Jack Auto® outdoors in a humid climate?

Yes, but ensure good airflow and avoid overcrowding. Its moderate mold resistance helps, but dense buds need dry air in late flowering to prevent issues.

Does this strain need a lot of nutrients?

No — it performs best with moderate feeding. Over-fertilizing can harm roots and reduce resin production. Stick to a balanced autoflowering nutrient line.

Is Black Jack Auto® good for beginners?

Absolutely. With a short cycle, forgiving nature, and high reward, it’s one of the best autoflowers for new growers.

How many plants can I grow per square meter?

Indoors, 9 plants in 11 L pots fit well under a 600W light. For larger pots (18–27 L), reduce to 4–6 plants/m² for optimal growth.

Personal Experience of Pevgrow’s CEO (Alan)

I’ve grown dozens of autoflowers, but Black Jack Auto® stands out for its balance of speed, potency, and flavor. I ran it under a 600W HPS with 18/6 lighting and got 510 g/m² in just 63 days — that’s insane for an auto. The buds were rock-hard, covered in trichomes, and smelled like a mix of citrus and church incense. I prefer curing it for 4 weeks to smooth the taste. One tip: don’t rush harvest. Wait until at least half the trichomes turn amber for a more balanced high. It’s now a staple in my rotation — fast, reliable, and always impressive.