Black Jack

Black Jack Feminized Cannabis Seeds by Sweet Seeds

Black Jack is a feminized cannabis seed strain from Sweet Seeds that crosses the resinous Black Domina with the legendary Jack Herer — producing a 50/50 indica-sativa hybrid built for heavy yields and a clean, uplifting smoke. With indoor harvests averaging 600g per square metre and THC levels between 16% and 21%, this is one of those strains that delivers on both the growing side and the smoking side without making you choose between the two.

Why Black Jack Seeds Deserve a Spot in Your Grow Room

Sweet Seeds bred Black Jack to be vigorous and forgiving — two words that matter more than any THC percentage when you're actually standing in front of your tent at week five. The Black Domina parentage brings dense, resinous bud structure and a compact flowering window of just 9 weeks. The Jack Herer side contributes stretch, lateral branching, and that aromatic profile people keep coming back for. The result is a plant that responds well to virtually every indoor growing method: SOG, SCROG, topping, LST — she takes it all in stride.

We've seen growers treat Black Jack as their reliable workhorse strain. It's not the flashiest name in the seed catalogue, but 600 grams per square metre indoors is no joke. Outdoors, expect roughly the same yield per plant, with the added bonus of watching her stretch to around 3 metres tall with a nearly circular canopy that fills out wide. If you're growing outdoors in a decent climate, harvest falls in the first half of October.

The honest limitation? At 3 metres outdoors, discretion goes out the window. If you need a compact outdoor plant, this isn't it. Indoors, though, she's manageable — the indica genetics keep internodal spacing tight enough that you won't lose control of your canopy height with a bit of training.

Black Jack Strain Profile: Flavour, Aroma, and What to Expect

Black Jack produces a very aromatic smell and taste that's free of any harsh, choking quality on the exhale. Think incense-sweet with a clean finish — the kind of smoke you can pass around without anyone coughing into their elbow. The terpene profile leans towards that classic Jack Herer spiciness layered over the darker, earthier notes from the Black Domina side.

With THC content sitting between 16% and 21% and CBD at around 0.6%, the effect is described as a clean, clear-headed high without the heavy comedown. Sweet Seeds specifically markets this as a social strain — the sort you'd roll before heading out rather than before melting into the sofa. That said, the indica backbone means there's enough body presence to keep things grounded. It's not racy or anxious; it's balanced.

According to research on cannabinoid profiling, quantitative analysis has revealed substantial phytochemical variation across cannabis cultivars, with total THC ranging from 0.41% to 15.64% in some sample sets (PMC13074809). Black Jack's 16-21% THC places it comfortably in the upper range — potent enough to be interesting, not so strong that a single puff sends a casual smoker sideways.

Growing Black Jack Feminized Seeds: Indoor and Outdoor

Black Jack feminized seeds are adapted for indoor environments, and that's where most growers will run them. The 50/50 genetic split means she stretches enough during the first two weeks of flower to fill a SCROG net nicely, but the indica side keeps her from bolting to the ceiling. A 9-week flowering period is about average — not the fastest finisher, but you're rewarded with heavy, resin-coated colas that justify every day of waiting.

1. Germinate seeds using the paper towel method or directly in a starter plug. Sweet Seeds feminized genetics mean every seed should produce a female plant — no need to sex them.
2. Transplant seedlings into their final containers once the first true leaves appear. Black Jack responds well to 11-litre pots indoors or directly into soil outdoors.
3. Veg for 3-4 weeks indoors under 18/6 lighting. Top once above the fourth node if you want to encourage that natural lateral branching.
4. Flip to 12/12 when the canopy fills roughly 70% of your growing space. Expect a moderate stretch of 50-80% during the first two weeks of flower.
5. Support branches from week 5 onwards — the buds get heavy. A trellis net or bamboo stakes prevent snapped laterals.
6. Harvest at 9 weeks of flower when trichomes show mostly cloudy with a few amber heads. Outdoor growers: aim for the first two weeks of October.

One thing we'd flag: Black Jack's vigour means she drinks heavily during mid-flower. If you're hand-watering, check your pots daily from week 4 onwards. Underwatering during the bulk phase is the easiest way to leave yield on the table.

Black Jack vs Other Jack Herer Crosses

The cannabis seed market is full of Jack Herer hybrids, so what sets Sweet Seeds' Black Jack apart? Mainly the Black Domina cross. Where most Jack crosses lean sativa-dominant and finish in 10-11 weeks, Black Jack pulls that down to 9 weeks flat while boosting yield density. The Black Domina parentage — itself a four-way cross of Northern Lights, Ortega, Hash Plant, and Afghan SA — brings a resin production that pure sativa-leaning Jacks can't match.

If you're comparing within the Sweet Seeds catalogue, their S.A.D. (Sweet Afghani Delicious) is the heavier indica option with faster flowering, but lower ceilings on both THC and yield. Black Jack sits in that sweet spot where you get sativa-quality effects with indica-level production numbers. For growers who want one strain to run all season, it's hard to argue against those 600g/m2 averages.