Critical Jack cannabis seeds packaging — Royal King Seeds UK
Hybrid
THC 20%
🎨 Creative
HybridFeminisedIn Stock

Critical Jack Feminised

Feminised PhotoperiodSee Lab Report →

Critical Jack Feminised cannabis seeds for UK growers. Hybrid · 20% THC · focused, relaxed, uplifted. 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 2026-09-01 on 350 seeds.

Germination rate: 98.7% (n=350)
Last QC test date: 2026-09-01
Indoor yield: 420-552 g/m² (avg across 12 verified grower reports)
Outdoor yield: 650-834 g/plant (avg across 3 verified grower reports)

About Critical Jack Feminised

Will Critical Jack finish outdoors in Britain? Yes, within the April to October season. The balanced genetics cope with what British weather does from one week to the next, from damp air on the west coast to the drier run of counties in the east. Flowering runs 60 days, which puts harvest in September or October for most of the country.

What yield is realistic? 625 g/m2 indoors is achievable with competent LED lighting and attention to feeding. Outdoors, 1200 g/plant is realistic in 50 litre pots or in prepared ground with full sun — and "full sun" is doing a lot of work in that sentence at these latitudes, so the position you pick in the garden matters more than the pot you buy. At 20% THC with a limonene-forward profile, the return on the effort is sound.

Is it forgiving? Reasonably. Anyone comfortable with pH, a feed schedule and a light timer will get a good result. It will not hold your hand, but it will not punish one missed watering either.

Further questions we get asked about Critical Jack

Which medium? For flavour, peat-free soil cut with about 30% perlite and amended slowly — fish, blood and bone, rock phosphate, seaweed meal, all of it available at any British garden centre. For weight, coco with fertigation at EC 1.4-1.8 through bloom. This hybrid performs in both; the choice is about what you want out of it.

How does it handle a British summer? Well enough, on hybrid vigour. Keep the root zone under 28°C with mulch or pale pots, and do not transplant into a heatwave. The more common British problem is the opposite one: a cold, wet July that never lets the plant dry out between waterings.

When do I switch to bloom feed? Inside the first week of visible pistils. The 50/50 balance shifts its demand quickly at the transition — phosphorus and potassium up, nitrogen down. Soil growers can top-dress with guano and sulphate of potash; coco and hydro should move to a low-nitrogen bloom formula straight away.

Indoors or outdoors? Both work, for different reasons. Indoors you own the flowering environment completely. Outdoors, across the April to October season, the plant gets a light intensity no domestic LED matches and can reach 1200 g/plant — at the price of accepting whatever the autumn does. Flowering: 60 days. Indoor yield: 625 g/m2. Outdoor yield: 1200 g/plant. Rated intermediate difficulty.

Flavour, aroma and effect

Critical Jack arrives in stages. The first draw at 20% THC brings a bright citrus edge that lifts off the palate immediately. The focused, relaxed, uplifted character follows within minutes, as a head and body effect at once. The mind stays clear while the muscles let go by degrees, which is what makes it adaptable — a small dose carries an afternoon, a larger one turns into an evening. The caryophyllene underneath adds a warmth that keeps the whole thing anchored.

Terpene breakdown

Primary: Limonene · Secondary: Caryophyllene · Tertiary: Linalool. How this profile survives the journey from flower to vapour depends on temperature. Low vaporisation, 180-188°C, keeps the caryophyllene and linalool audible over the limonene base. Run it hotter, or burn it, and the three collapse into one note — pleasant enough, but none of the complexity that made it worth choosing.

Who it suits

Who does well with Critical Jack? Indoor growers who want the timeline under their own control. Outdoor growers who want to choose when flowering starts. Anyone with the room and the patience to veg it properly before flipping. Difficulty is rated intermediate, which means a moderate learning curve that rewards attention without demanding a laboratory.

Effects

🧠Focused
76% of people reported feeling Focused
😌Relaxed
65% of people reported feeling Relaxed
😎Uplifted
58% of people reported feeling Uplifted
😊Happy
51% of people reported feeling Happy
🤩Creative
50% of people reported feeling Creative
🤗Euphoric
40% of people reported feeling Euphoric
🤤Hungry
34% of people reported feeling Hungry
😴Sleepy
31% of people reported feeling Sleepy
😆Giggly
24% of people reported feeling Giggly

Strain Type

Indica 50%Sativa 50%

Strain Data Sheet

🧬THC20% - 25% (High)
🌿LineageBalanced Hybrid (Undisclosed Lineage)
🔬TypeFeminised Hybrid
🌡ClimateTemperate, adaptable
📅HarvestLate Sept – Oct, UK outdoor (typical)
📏Height100 – 160 cm (typical)
⚖️YieldHigh
🏠Yield Indoor625 g/m2
🌳Yield Outdoor1200 g/plant
⏱Flowering Time60 days

Packaging

Resealable +
RK
Royal King Seeds
Photoperiod
Feminised Premium
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.
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Critical Jack Feminised
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🛡️Aluminium interior lining
🏷️Protective sticker
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🔢Scratchable serial number

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Critical Jack Feminised — 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 IBL
Generations
5+
Breeding Programme
Inbred Line (IBL) — multi-generation inbred selection
Stabilisation Notes — What This Means for Your Grow

Five generations of inbred selection on the original early-2000s legacy Critical Jack cuts. We were not chasing a redesign — we locked the pack-to-pack uniformity that earned this cultivar its reputation. Whatever the next pack throws is what the last pack threw.

Breeding Goal

Restabilise a early-2000s legacy cultivar to contemporary uniformity standards.

Selection Focus

Chosen for terpene profile, vigour, structure and finish-time consistency.

Pollen / Mother Source

Royal King Genetics select-mother programme — pollen drawn from an internally maintained reversed-female line.

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