Sour Jack by Karma Genetics

Back in 2010, when the forum scene on ICMag and THCFarmer was at its peak, Karma Genetics started passing out test seeds of Sour Jack, and the community absolutely lost its mind. This sativa-dominant monster was born in Amsterdam, crossing a notoriously finicky Sour Diesel IBL female with a stud Jack Herer male (the famous Jack #22). Karma wasn't just messing around; the specific goal was to fix the loose, open bud structure of the Sour Diesel while keeping that face-melting flavor. The Jack male tightened everything up, turning the airy diesel flowers into rock-hard, spear-like colas that yield like crazy. It’s one of those legendary crosses that proved exactly why Karma is considered a master breeder.

You better have some ceiling height if you plan on dropping Sour Jack beans in your room. This plant wants to reach for the sky, inheriting all that aggressive sativa stretch from both parents. Real growers know you have to top her early and aggressively prune the lowers to keep her manageable. She usually runs anywhere from 9 to 12 weeks, but the wait is completely justified when you see the massive, pillar-like flower clusters she produces. The resin production is off the charts, and the branches often need heavy support by the end of flower just to hold up the sheer weight of the buds.

When it comes to the smoke, it’s a high-octane rocket ride. You're getting slapped with a terp profile that smells like lemon candy soaked in jet fuel, with sharp hits of pine and menthol on the back end. The high is electric, heady, and incredibly clear, perfect for a wake-and-bake that gets your heart racing. It’s not for the faint of heart or anyone prone to anxiety, but for sativa heads chasing that energetic, classic early-2000s potency, Sour Jack remains an absolute holy grail in the stash jar.

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Similar strains

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🧬 Explore the family: Sour Diesel IBL · Jack Herer · Aliens JackD Up · Galactic Jack · SinFully Sour · SourFlame OG · Sin City Seeds - Rappers Delight · Triple Cherry Diesel · White Cranberries · SinCityDiesel

Ancestry Pedigree

Growing Sour Jack: what to expect

As a sativa-leaning plant, plan for a big stretch after the flip (often 100–200%) — flip earlier than feels natural and keep training options ready. Sativa-leaning plants also generally prefer a lighter feed than heavy indicas. Growers familiar with Sour Diesel IBL or Jack Herer will recognize much of its behavior. Whatever the listing says, the cut in YOUR tent is the ground truth: log feedings, readings, and photos, and let the trends — not the label — drive decisions.

Sour Jack FAQ

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Facts compiled from public breeder listings. Growing Sour Jack? A structured journal — with your feedings, readings, and photos — is how you find what THIS cut actually wants.

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