Indica · ILGM Genetics
Granddaddy Purple
Granddaddy Purple is the Ken Estes indica that codified the modern purple-strain category. It is a cross of Purple Urkle and Big Bud, bred in 2003 in the San Francisco Bay Area, and the dominant phenotypes throw heavy, grape-shaped buds with deep purple coloration as night temperatures drop below 18 °C. Flowering finishes in eight to nine weeks indoors, and the strain ranks as one of the highest-yielding indicas in the legal market.
Reviewed 2026-05-23· Sources: seedfinder.eu, Ken Estes interviews
Potency
- THC range
- 17–23%
- Typical THC
- 20%
- CBD
- up to 0.1%
Flowering
- Indoor weeks
- 8–9 wk
- Difficulty
- Easy
- Climate
- cool nights, Mediterranean
Yield & size
- Indoor
- 550-650 g/m²
- Outdoor
- 600-800 g/plant
- Height
- 90-120 cm
Indica / sativa ratio
Terpene profile
The aromatic compounds below shape how Granddaddy Purple smells, tastes, and ultimately feels in the body.
- dominant
Myrcene
Sedating, musky, herbal — commonly linked to couch-lock effects.
- secondary
Caryophyllene
Peppery and spicy — the only terpene that binds CB2 receptors, studied for anti-inflammatory action.
- secondary
Pinene
Alert and pine-forward — associated with mental clarity and bronchodilation.
- minor
Linalool
Floral and lavender-like — calming, often noted for sleep and anxiety support.
Reported side effects
Lineage
Granddaddy Purple traces to Purple Urkle × Big Bud. The cross sits in the Purple family, which influences both the terpene profile and the flowering structure described above.
Genetic family tree
Documented parents and grandparents for Granddaddy Purple 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 Granddaddy Purple
Granddaddy Purple is a parent of 4 strains in the broader catalogue. These are crosses that carry Granddaddy Purple 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
- topping, lst
Feed schedule for Granddaddy Purple
These EC and NPK targets are starting points calibrated for the strain's Indica lean and easy 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
- 1.1-1.3 EC
- Early flower
- 1.2-1.4 EC, NPK 2-3-4
- Mid flower
- 1.5-1.7 EC, NPK 1-4-6
- Late flower
- 1.3-1.5 EC
- Final week
- Plain pH-balanced water for the last 5-7 days.
Full breakdown of feed math, runoff testing, and salt buildup in our nutrient guide.
What to expect through the grow cycle
Granddaddy Purple 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 Granddaddy Purple 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 Granddaddy Purple. Plants establish root structure, leaf canopy, and node count before flower triggering, with a easy difficulty rating shaping how forgiving the early canopy work tends to be.
- Stretch (weeks 5-7)
- Granddaddy Purple 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 Granddaddy Purplenote 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 Granddaddy Purple 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 Granddaddy Purple 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 Granddaddy Purple runs end here, within the 8-9 week flowering range reported by the breeder.
Flavor & aroma
Reported effects
Common questions about Granddaddy Purple
How do I get Granddaddy Purple to actually turn purple?
Drop night-time temperatures into the 15-18 °C range during the last two weeks of flower. Without the cold swing most phenotypes finish green.
Is GDP good for sleep?
Yes — it is one of the most-recommended strains for insomnia because the indica side dominates the high within thirty minutes.
Breeder of record
ILGM Genetics
View breeder profile and other strains →
More from ILGM Genetics
Strains similar to Granddaddy Purple
These picks lean on the same terpene profile and parent genetics as Granddaddy Purple — 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.
