Black Jack cannabis seeds packaging — Royal King Seeds UK
SativaAuto
THC 23%
😊 Beginner Pick
SativaAutoflowerIn Stock

Black Jack Auto

AutoflowerSee Lab Report →

Black Jack Auto cannabis seeds for UK growers. Sativa · 23% THC · euphoric, focused, energetic. Discreet UK delivery, priced in GBP.

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Royal King Genetics — first-party test batch

Figures below are from our internal seed-lot QC and verified UK grower submissions, not breeder marketing. Determined from a single batch tested 2026-08-31 on 200 seeds.

Germination rate: 98.1% (n=200)
Last QC test date: 2026-08-31
Indoor yield: 360-474 g/m² (avg across 12 verified grower reports)
Outdoor yield: 626-858 g/plant (avg across 7 verified grower reports)

About Black Jack Auto

Germination and early veg, days 1-14. Black Jack seeds generally crack inside 48 hours on damp kitchen roll and break the surface around day three. Early growth came in fast and upright, the first narrow leaves reaching for the light from the start. Five nodes by the end of week two with obvious space between them, which tells you what the stretch is going to do later. Damping off is rare around 70% relative humidity, which is also roughly what an unheated British room sits at in spring.

Veg, weeks 3-6. Vertical growth needed managing. Even with low-stress training from week three it wanted to climb, so the main stem went over at a right angle in week four; the secondaries caught up and the canopy was flat by week six.

Bloom, weeks 1-9. This is where the 20/80 balance in Black Jack showed itself. The pinene came up in week three and kept building; trichome cover was obvious to the naked eye from week five. Indoor yield: 400-550 g/m2. Height: 40-110 cm. THC testing at 23%. Rated intermediate.

The rest of the diary

Mid-bloom, weeks 4-6. The change came quickly. Sites that were loose and wispy at week three closed into defined colas. The buds kept extending lengthwise, stacking fresh calyxes along the stems. The secondaries outperformed expectations: the open structure let light reach sites that a bushier plant would have shaded out completely.

Ripening, weeks 7-9. Feeding dropped to plain water for the last ten days. The pinene got strong enough that carbon filtration stopped being optional in a terraced house. Trichomes ran clear to milky across the final fortnight, amber showing on sugar leaves first. Around 15% amber on the calyxes is a common place to stop.

Drying and curing. Whole plant hung in the dark at 17°C and 58% humidity for twelve days — both numbers held by a dehumidifier, because an October room in this country will not hold either on its own. Stems snapped rather than bent, which is the test worth trusting. Four weeks in glass followed, burped twice daily for the first fortnight and once daily after. Final weight matched the 400-550 g/m2 figure. The limonene was far more present after the cure than at harvest, which is the argument for curing properly: the process makes flavour rather than merely keeping it.

Flowering: 9 weeks from germination. Indoor yield: 400-550 g/m2. Outdoor yield: 40-250 g/plant. Plant height: 40-110 cm. Rated intermediate difficulty. Regular seeds with autoflowering genetics.

Flavour, aroma and effect

Black Jack arrives in stages. The first draw at 23% THC brings clean resin, like woodland after rain. The euphoric, focused, energetic character follows within minutes, arriving as sharpened attention. Colour reads brighter, music reads busier, and conversation wanders further than it would otherwise. It holds for two to three hours on a plateau rather than a spike. The limonene underneath adds a lift that stops it turning heavy.

Terpene breakdown

Primary: Pinene · Secondary: Limonene · Tertiary: Caryophyllene. This combination turns up often in cultivars that win things, and it is usually the one growers comment on when a jar is opened for the first time after curing. Pinene anchors the aroma, limonene occupies the middle, and caryophyllene sits behind both — which is the part that separates this strain from others sharing its primary terpene.

Who it suits

Who does well with Black Jack? Balcony growers in flats from Brighton to Glasgow. Anyone wanting one quick outdoor crop rather than a long project. Indoor growers short of headroom. The autoflowering genetics run on their own clock, so there is no light schedule to manage, no anxiety about light leaks, and harvest comes 10-12 weeks from germination whatever the season is doing. Difficulty is rated intermediate, which means a moderate learning curve that rewards attention without demanding a laboratory.

Effects

🤗Euphoric
74% of people reported feeling Euphoric
🧠Focused
69% of people reported feeling Focused
🤑Energetic
57% of people reported feeling Energetic
😊Happy
51% of people reported feeling Happy
🤩Creative
50% of people reported feeling Creative
😎Uplifted
38% of people reported feeling Uplifted
🗣️Talkative
30% of people reported feeling Talkative
💪Motivated
31% of people reported feeling Motivated
😆Giggly
24% of people reported feeling Giggly

Strain Type

Indica 20%Sativa 80%

Strain Data Sheet

🧬THC23% - 28% (High)
🌿LineageBlack Domina × Jack Herer
🔬TypeAutoflower Sativa
🌡ClimateAll climates (adaptable)
📅Harvest≈ 10 – 11 weeks from seed (typical)
📏Height40-110 cm
⚖️YieldHigh
🏠Yield Indoor400-550 g/m2
🌳Yield Outdoor40-250 g/plant
⏱Flowering Time9 weeks from germination

Packaging

Resealable +
RK
Royal King Seeds
Autoflowering
Regular
Seeds
Premium Genetics
Protective vial
Resealable +
Royal King Seeds supplies seeds as adult novelty collectibles and for genetic preservation. Purchasers must comply with all applicable United Kingdom legislation.
1
Black Jack Auto
royalkingseeds.co.uk
IG
FB
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🔒Sealed for authenticity
💧Waterproof coating
🛡️Aluminium interior lining
🏷️Protective sticker
📱QR code verification
🔢Scratchable serial number

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Black Jack Auto — Breeder Information

Royal King Genetics

Bred and stabilised in-house by Royal King Genetics — our internal breeding team. Every batch is QC'd and germ-tested above 99% before it ships. Read the full breeding process and about page.

Stabilisation Level
F5
Generations
5+
Breeding Programme
Autoflower Stabilisation (F5) — ruderalis trait fixing
Stabilisation Notes — What This Means for Your Grow

Black Jack is our F5 autoflower line. Five rounds of selection have fixed both the autoflower trigger and the high-energy terpene expression the cultivar is known for. The recessive ruderalis trait demands this depth of work to express uniformly.

Breeding Goal

Lock the autoflower trait in Black Jack through five generations of selection.

Selection Focus

Chosen for vigour, manageable stretch and the cerebral terpene profile sativa growers buy this strain for.

Pollen / Mother Source

Royal King Genetics in-house breeder room — pollen taken from a generation-tracked sibling-male line.

Last Batch QC Verified
16 September 2026· 99%+ germination