Indica · Sensi Seeds
G13
G13 is the long-mythologized indica clone-only line said to have originated as a U.S. government research strain at the University of Mississippi during the 1970s, allegedly leaked to a private breeder and then propagated through the underground until Sensi Seeds released a seed-form selection in the late 1990s. The factual record is thinner than the legend — no government documentation confirms the Mississippi origin — but the working line that arrived in Dutch hands by the early 1990s has been heavily selected since and produces dense, resinous indica buds with pine, citrus, and earthy hash notes. The high is heavy and sedative, leaning toward couch-lock and body relaxation, and the THC content from properly grown G13 phenotypes lands in the high teens to low twenties. The Sensi seed-form release is the canonical commercial version, though several other banks have released G13 crosses with Hash Plant, NL, and Skunk parents over the years. G13 is most useful today as a breeding parent for indica-leaning resin lines rather than as a daily-driver strain.
Reviewed 2026-05-23· Sources: seedfinder.eu, Sensi Seeds catalogue, High Times archive
Potency
- THC range
- 18–24%
- Typical THC
- 21%
- CBD
- up to 0.3%
Flowering
- Indoor weeks
- 8–9 wk
- Difficulty
- Moderate
- Climate
- Mediterranean, warm temperate, indoor
Yield & size
- Indoor
- 425-525 g/m²
- Outdoor
- 500-700 g/plant
- Height
- 90-130 cm
Indica / sativa ratio
Terpene profile
The aromatic compounds below shape how G13 smells, tastes, and ultimately feels in the body.
- dominant
Myrcene
Sedating, musky, herbal — commonly linked to couch-lock effects.
- secondary
Pinene
Alert and pine-forward — associated with mental clarity and bronchodilation.
- secondary
Caryophyllene
Peppery and spicy — the only terpene that binds CB2 receptors, studied for anti-inflammatory action.
- minor
Humulene
Hoppy and earthy — appetite-suppressing and shared with hops and sage.
Reported side effects
Lineage
G13 traces to Afghani indica (uncertain origin). The cross sits in the Afghan indica family, which influences both the terpene profile and the flowering structure described above.
Genetic family tree
Documented parents for G13 based on breeder catalogues. Library entries are clickable; ancestors not yet documented on this site appear in a lighter, non-linked box.
Strains crossed with G13
G13 is a parent of 3 strains in the broader catalogue. These are crosses that carry G13 genetics on at least one side of the cross.
Grow profile
Grow profile
- Indica / sativa
- 90% / 10%
- Flowering days
- 56–63 days
- Stretch
- Low
- Pest resistance
- Moderate
- Mold resistance
- Moderate
- Training methods
- lst, topping, scrog
Feed schedule for G13
These EC and NPK targets are starting points calibrated for the strain's Indica lean and moderate difficulty rating — not gospel. Drop 15-20% off any EC ceiling on your first run and let the plant tell you where it actually wants to feed.
Suggested feed schedule
- Late veg
- 1.4-1.6 EC
- Early flower
- 1.5-1.7 EC, NPK 2-3-4
- Mid flower
- 1.8-2.0 EC, NPK 1-4-6
- Late flower
- 1.6-1.8 EC
- Final week
- Plain pH-balanced water for the last 7-10 days; light flush if you ran nutrients on the higher end.
Full breakdown of feed math, runoff testing, and salt buildup in our nutrient guide.
What to expect through the grow cycle
G13 is documented with a 9-week flower and a compact stretch typical of indica-leaning structure. The visual below maps a documented 13-week cycle built from 4weeks of vegetative growth and the strain's published flowering window.
Published grow reports for G13 concentrate the most observational notes on the late-flower ripening window. This timeline is descriptive — it reflects what reports document, not a how-to. Actual week-to-week behaviour varies with phenotype, light intensity, pot size, and environment.
Phase details
- Veg (weeks 1-4)
- The documented vegetative period for G13. Plants establish root structure, leaf canopy, and node count before flower triggering, with a moderate difficulty rating shaping how forgiving the early canopy work tends to be.
- Stretch (weeks 5-7)
- G13 is documented as having low stretch. Reports describe the plant roughly doubling in height during this phase as the indica-leaning structure establishes its final flowering frame.
- Bud sites (weeks 8-9)
- Pre-flowers form at the nodes and calyxes begin to develop. Grow reports for G13note this as the window where the canopy's eventual bud distribution becomes visible.
- Bud development (weeks 10-11)
- Flowers thicken and calyxes fatten through this phase. Documented G13 runs show the bulk of visible flower mass accumulating here, with resin production accelerating toward the end.
- Ripening (week 12)
- Trichomes transition from clear toward cloudy and amber. Reports for G13 describe the Myrcene-led terpene profile maturing through this window, with aroma sharpening week over week.
- Final (week 13)
- Calyx swelling is documented as complete and the harvest window opens. Published G13 runs end here, within the 8-9 week flowering range reported by the breeder.
Flavor & aroma
Reported effects
Common questions about G13
Is the government-research story behind G13 actually true?
There is no public documentation from the University of Mississippi or the federal cannabis research program confirming the leak story. The narrative entered cannabis culture through Neville Schoenmakers and other Dutch breeders in the 1980s, and the modern commercial line traces to that period rather than to verified government stock.
How does G13 differ from G13 Haze?
G13 is a pure indica-dominant cut. G13 Haze is a Barney's Farm hybrid crossing G13 with a Haze parent, which lengthens flowering, increases stretch, and shifts the high toward sativa cerebral effects. The two strains share a name but not a use case.
Breeder of record
Sensi Seeds
View breeder profile and other strains →
More from Sensi Seeds
Strains similar to G13
These picks lean on the same terpene profile and parent genetics as G13 — shared dominant terps, overlapping lineage, and matching indica/sativa lean. No star ratings or popularity contests, just overlap on the traits that actually drive a similar grow and smoke.