Jack Flash cannabis seeds packaging — Royal King Seeds UK
Hybrid
THC 19%
🎨 Creative
HybridFeminisedIn Stock

Jack Flash Feminised

Feminised PhotoperiodSee Lab Report →

Jack Flash Feminised — hybrid cannabis seeds suited to UK growing conditions. 19% THC with creative, energetic, relaxed effects. Fast, discreet UK delivery.

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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 2026-09-22 on 450 seeds.

Germination rate: 97.8% (n=450)
Last QC test date: 2026-09-22
Indoor yield: 439-566 g/m² (avg across 15 verified grower reports)
Outdoor yield: 529-784 g/plant (avg across 6 verified grower reports)

About Jack Flash Feminised

Will Jack Flash 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 55 to 75 days, which puts harvest in September or October for most of the country.

What yield is realistic? 450 gr/m² indoors is achievable with competent LED lighting and attention to feeding. Outdoors, around 600 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 19% THC with a myrcene-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 Jack Flash

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 60/40 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 around 600 g/plant — at the price of accepting whatever the autumn does. Flowering: 55 to 75 days. Indoor yield: 450 gr/m². Outdoor yield: around 600 g/plant. Plant height: up to 180 cm (indica pheno ~100 cm). Rated intermediate difficulty.

What Jack Flash is actually like

Growers report creative, energetic, relaxed as the defining characteristics and our own notes agree. At 19% THC this hybrid sits where the balance is the selling point. Taken small it stays functional; taken larger it relaxes properly. The ${indica}/${sativa} split means the direction is set by how much you take rather than fixed by the genetics. The Myrcene/Limonene pairing leaves earth and faint sweetness on the palate, with fruit at the end.

Best suited to most occasions — the dose does the steering.

Terpene breakdown

Primary: Myrcene · Secondary: Limonene · Tertiary: Pinene. 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. Myrcene anchors the aroma, limonene occupies the middle, and pinene sits behind both — which is the part that separates this strain from others sharing its primary terpene.

Who it suits

Jack Flash suits growers with the basics in place. Understand pH, rough nutrient ratios and light cycles before you commit to it; it asks for competence rather than expertise. Photoperiod genetics leave plant size and harvest date under your control — veg longer for bigger plants, or flip early when space is short. The April to October season accommodates a bloom of 55 to 75 days comfortably for outdoor growers across the country.

Effects

🤩Creative
77% of people reported feeling Creative
🤑Energetic
64% of people reported feeling Energetic
😌Relaxed
58% of people reported feeling Relaxed
😊Happy
51% of people reported feeling Happy
🤗Euphoric
47% of people reported feeling Euphoric
😎Uplifted
38% of people reported feeling Uplifted
🤤Hungry
34% of people reported feeling Hungry
😴Sleepy
31% of people reported feeling Sleepy
😆Giggly
24% of people reported feeling Giggly

Strain Type

Indica 60%Sativa 40%

Strain Data Sheet

🧬THC19% - 23% (Medium-High)
🌿LineageBalanced Hybrid (Undisclosed Lineage)
🔬TypeFeminised Hybrid
🌡ClimateTemperate, adaptable
📅HarvestLate Sept – Oct, UK outdoor (typical)
📏Heightup to 180 cm (indica pheno ~100 cm)
⚖️YieldTypical for type
🏠Yield Indoor450 gr/m²
🌳Yield Outdooraround 600 g/plant
⏱Flowering Time55 to 75 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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Jack Flash Feminised
royalkingseeds.co.uk
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🔒Sealed for authenticity
💧Waterproof coating
🛡️Aluminium interior lining
🏷️Protective sticker
📱QR code verification
🔢Scratchable serial number

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Jack Flash 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
IBL Heritage Programme — five-generation inbred fixing
Stabilisation Notes — What This Means for Your Grow

When a strain has been kicking around since the late-1990s legacy, the question becomes whether the modern seed line still grows like the original cut. Our F5 IBL on Jack Flash answers that — five rounds of selection have re-locked the structural balance that made the cultivar a benchmark.

Breeding Goal

Restabilise a late-1990s legacy cultivar to contemporary uniformity standards.

Selection Focus

Chosen for balanced indica/sativa expression, terpene fidelity and pack-to-pack uniformity.

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