🍇 Auto Granddaddy Purple Feminised Seeds — GDP Genetics on a Fixed Timeline

Auto Granddaddy Purple feminised seeds carry the Purple Urkle × Big Bud genetics that made Granddaddy Purple a 2015 High Times Cannabis Cup Best Indica winner — on a fixed 63–70 day seed-to-harvest timeline that flowers automatically without a light schedule change. The Ruderalis cross reduces yield and THC relative to the photoperiod — real-world grows produce ~18–22% versus 20–27% for the photoperiod, and indoor yield sits at up to 400 g/m² versus 500 g/m². What it preserves is the GDP character: the grape and berry terpene profile that made the strain famous, the deep purple colouration triggered by cool nights, and the sedative indica body effect that Ken Estes bred specifically for therapeutic pain relief and sleep support.

Why choose the auto over the photoperiod: The fixed timeline is the whole reason to run this version. Outdoor growers without light control can't reliably trigger photoperiod GDP's flowering using natural day length unless the planting window aligns precisely with the season. The auto removes that constraint entirely — plant when conditions suit, harvest 63–70 days later. For indoor perpetual setups, the fixed cycle allows staggered harvests without managing separate veg and flower spaces. The compact 60–100 cm height is also a practical advantage for balcony grows, small tents, and discreet outdoor situations where full-size photoperiod plants aren't practical.

What the Ruderalis cross costs: THC drops from 20–27% to ~18–22%. The sedative effect is genuine and present but lighter than the photoperiod at equivalent doses. Outdoor yield per plant drops significantly — 80–120 g versus up to 600 g for the photoperiod with a full Australian summer veg. The grape terpene profile carries through well with a proper flush and cure, but the intensity is reduced. This is the right choice when the timeline or grow situation makes the photoperiod impractical — not when maximum potency or yield is the brief.

What Auto GDP does well:

• Grape terpene profile: The sweet grape and berry character that defines GDP carries through the Ruderalis cross reliably — with a proper cure the flavour is recognisably Granddaddy Purple
• Purple expression: The anthocyanin genetics are present in the auto version. Cool nights (15–18°C) in the final 2–3 weeks trigger deep purple to near-black colouration. January plantings that harvest in late March/April benefit from natural Australian autumn temperatures
• Therapeutic body effect: At ~18–22% THC with myrcene-dominant terpenes, the sedative and analgesic effect is still meaningful — lighter than the photoperiod but substantially above most auto indicas
• Season flexibility: Plant September through March in Australia and harvest on a 63–70 day fixed schedule — two or three outdoor runs per season are achievable
• Compact footprint: 60–100 cm suits small indoor tents and discreet outdoor situations. No light flip required

Purple colouration in the auto: The anthocyanin genetics that produce GDP's signature deep purple are fully present in the auto version. Temperature triggers them the same way as the photoperiod — 15–18°C nights for the final 2–3 weeks. For maximum colour expression outdoors, a January planting in most Australian states targets a late March/April harvest when natural night temperatures hit that range. Summer harvests will still produce quality buds with good flavour and potency, but colour development will be less dramatic without the cool nights.

🍇 Auto GDP Effects & Experience

Onset (10–20 minutes): Gradual rather than sudden. Thoughts slow, stress releases, a quiet calm arrives before the body effects establish themselves. No anxiety, no rush. The GDP character — gentle mental settling before heavy physical relaxation — is present in the auto version.

Early phase (20–45 minutes): Body relaxation begins spreading. Muscle tension releases, physical ease arrives. At moderate doses this is still functional — the auto's slightly reduced THC compared to the photoperiod means the sedation builds more gradually. Good for quiet evening activities, winding down, or preparing for sleep.

Mid-phase (45–90 minutes): The 70% indica genetics dominate. Body relaxation is deep and complete. Motivation to engage in active tasks drops significantly. The mental state remains clearer than many heavy indicas at this potency — the mental clarity alongside physical sedation that distinguishes GDP is present, though less pronounced than in the full-potency photoperiod.

Late-phase (90–150 minutes): Full body sedation. Sleep follows naturally for most users at typical doses. Appetite increases strongly. The progression is gradual — this is not a sudden knock-out, but an extended settling into rest.

Duration: 2–4 hours at typical doses with residual relaxation extending beyond that. The long tail is valuable for sleep applications — users report sustained sleep rather than waking mid-cycle.

Potency consideration: At ~18–22% THC, Auto GDP is solid-to-strong by auto standards. Noticeably lighter than the photoperiod version at equivalent doses, but meaningfully stronger than most ruderalis-heavy autos at this price point. The myrcene-dominant terpene profile amplifies the sedative effect above what the raw THC figure alone suggests.

Flavour profile: Sweet grape on the inhale — fruity, candy-like, genuinely similar to the photoperiod's characteristic aroma. Mixed berry notes follow with floral and earthy undertones. With a proper 3–4 week cure the grape expression sharpens significantly. Don't assess the flavour from fresh-dried material — the terpene profile isn't fully developed until the cure is complete.

Common uses (anecdotal): Insomnia and sleep support, chronic pain management, evening stress relief, muscle tension, anxiety reduction, appetite stimulation. Ken Estes bred the original GDP for these therapeutic applications, and the auto version targets the same use cases at a slightly more accessible potency level.

🌱 Growing Auto Granddaddy Purple Feminised Seeds — Complete Guide

(The following is provided for ACT licence holders and growers in legal jurisdictions overseas.)

Experience level required: Intermediate. Auto GDP is not a beginner strain despite the autoflower format. The GDP genetics carry some nutrient sensitivity, and the fixed timeline means mistakes in the first three weeks — overwatering, overfeeding, transplant stress — follow through to harvest without recovery time. Growers who've completed a successful auto run before will find Auto GDP manageable and rewarding. True beginners should build experience with a more ruderalis-robust auto first.

Critical auto rules — before germination:

• Start in the final container. Germinate directly into the pot the plant will finish in — 10–15 L indoors, 15–20 L outdoors. Transplanting an auto causes stress the fixed timeline cannot recover from
• No transplanting. Non-negotiable
• Feed light in weeks 1–3. Start at 1/4 strength. The GDP genetics show nutrient sensitivity faster than ruderalis-dominant autos
• Manage airflow. The bushy indica structure creates a dense canopy that needs air movement — this matters from early flower onward

Flowering: Auto GDP initiates flowering automatically at 3–4 weeks from germination. Seed to harvest runs approximately 63–70 days. Check trichomes from week 8. Harvest at 20–30% amber for the characteristic GDP body effect. Don't harvest early — the potency and grape flavour both develop in the final week.

Height and structure: Compact and bushy at 60–100 cm with the classic GDP indica architecture — sturdy central cola with dense lateral branching. The compact structure suits small tents and discreet outdoor grows. LST from week 2–3 opens the canopy and meaningfully improves yield and airflow.

Training:

LST (Low-Stress Training): The recommended approach. Begin tying down the main stem at week 2–3 to open the canopy and expose lower bud sites. The bushy GDP structure responds well to LST — more productive sites to expose than with single-cola auto genetics.

Topping: Not recommended. The fixed timeline doesn't allow the recovery time that topping requires to produce a net yield benefit.

Defoliation: Light only — remove leaves directly blocking bud sites in early flower. The canopy needs airflow but stripping it costs yield during the fixed timeline.

Feeding strategy:

Seedling (days 1–14):

• Plain water or 1/4 strength maximum
• Do not feed full strength — overfeeding at this stage is the most common auto growing mistake

Early veg / pre-flower (days 14–28):

• Build to 1/2 strength by week 3
• EC range: 0.8–1.2
• Watch tips for browning — GDP genetics show nutrient stress faster than ruderalis-heavy autos

Flower (days 28–60):

• Transition to bloom nutrients — reduce nitrogen, build phosphorus and potassium
• EC range: 1.2–1.6 — the Big Bud genetics tolerate slightly higher feeding than lighter autos but don't push beyond this
• Back off nitrogen firmly from week 6 — excess nitrogen in late flower affects flavour and delays ripening

Final flush (last 7–10 days):

• Plain pH-adjusted water only
• Important for the grape terpene profile — a proper flush improves the clean fruit flavour that GDP is known for

Climate:

Temperature:

• 22–26°C through veg and early flower
• 20–24°C in mid-to-late flower
• Drop to 15–18°C nights for the final 2–3 weeks — this is the trigger for purple colour development
• Don't go below 12°C — overly cold temperatures slow growth and risk mould in dense buds

Humidity:

• Seedling: 60–70% RH
• Veg: 50–60% RH
• Flower: 40–50% RH, dropping to below 40% in late flower
• The dense GDP bud structure is vulnerable in high humidity — strict management from week 5 onward

Light:

• 18/6 is the standard indoor schedule — flowers on any cycle
• 20/4 marginally better for yield
• PPFD targets: 400–500 µmol/m²/s early, 600–800 µmol/m²/s in flower
• Outdoors: full sun position, 6+ hours direct light minimum

Common issues:

Mould in late flower: The dense indica bud structure traps humidity without adequate airflow. Oscillating fans, light defoliation in early flower, and strict humidity management below 45% from week 5 prevent the most common late-harvest failure.

Harvesting too early: The full GDP effect and grape flavour develop in the final week. Chopping at week 8 because the trichomes look mostly cloudy misses the sedative depth the genetics are capable of. Wait for 20–30% amber.

Overfeeding early: GDP genetics show nutrient stress faster than ruderalis-dominant autos. Start at 1/4 strength for weeks 1–3 and watch the tips. Nutrient burn in the seedling phase costs development time the fixed timeline can't recover.

Rushing the cure: The grape terpene profile isn't fully expressed at harvest. It develops during the cure. Three to four weeks in sealed jars with daily burping produces material that tastes recognisably like GDP. Fresh-dried material doesn't.

🏠 Indoor Growing (Australia)

• Seed to harvest: 63–70 days fixed — no light flip required
• Yield: Up to 400 g/m² under quality lighting with LST
• Container: Start and finish in 10–15 L — no transplanting
• Light schedule: 18/6 recommended — flowers on any schedule
• Height: 60–100 cm — suits tents from 60 cm × 60 cm upward
• Training: LST from week 2–3 — the bushy GDP structure responds well and meaningfully improves yield and canopy airflow
• Temperature: Drop nights to 15–18°C for final 2–3 weeks for purple expression
• Aroma: Carbon filtration essential from week 6 — the grape aroma is strong, distinctive, and builds quickly
• Cycles per year: 5–6 complete indoor runs annually achievable with the 63–70 day timeline
• Cure: 3–4 weeks minimum in sealed jars — critical for grape terpene expression

🌿 Outdoor Growing (Southern Hemisphere / Australia)

• Harvest timing: ~63–70 days from planting — not season-dependent. Plant September through March for warm-weather runs
• Yield: 80–120 g per plant in good conditions — compact size limits total production compared to the photoperiod
• Container: 15–20 L minimum — start in the final pot, no transplanting
• Site: Full sun, 6+ hours direct light, good drainage, airflow around the plant
• Multiple runs: Three outdoor runs per season are achievable — plant September (harvest Nov), January (harvest Mar), and a late March planting for a June harvest in warmer states
• Purple expression: For maximum colour, plant December or January and target a late March/April harvest when natural night temperatures drop to 15–18°C across most Australian states. Summer harvests (September/October planting) produce quality buds with good potency but less colour development
• Climate suitability: Handles Australian conditions well. Warm summer days suit the indica veg phase. The compact height makes placement and concealment practical. Watch humidity in coastal Queensland and NSW from week 5 of flower

🗓️ Auto GDP Week-by-Week Grow Guide

Auto GDP runs on a fixed 63–70 day timeline. The dense bushy indica structure means airflow management is more important with this strain than with lighter autos. Setup before germination matters more than problem-solving during the grow.

🔍 Auto GDP — Common Myths vs Reality

🍇 Auto GDP vs GDP Feminised — Which One?

Choose the auto if you need a fixed 63–70 day timeline, compact height, or outdoor season flexibility. Choose the GDP Feminised if maximum yield, full therapeutic potency, and the ability to keep mother plants are priorities.

🍇 Is Auto GDP Right for Your Grow?

❓ Frequently Asked Questions — Auto Granddaddy Purple Feminised Seeds

🍇 What is Auto Granddaddy Purple?

Auto Granddaddy Purple feminised seeds are an autoflowering version of the award-winning Granddaddy Purple strain — the Purple Urkle × Big Bud cross bred by Ken Estes in California's Bay Area in 2003. The Ruderalis genetics added to the cross trigger flowering automatically at 3–4 weeks from germination regardless of light cycle, with seed to harvest running approximately 63–70 days on a fixed timeline. The characteristic GDP terpene profile — sweet grape, mixed berry, earthy undertones — and deep purple colouration both carry through into the auto version with a proper flush and cure.

⏱ How long does Auto GDP take from seed to harvest?

Approximately 63–70 days (9–10 weeks) from germination. This is a fixed timeline — the plant flowers and finishes on its own schedule. GDP Auto tends toward the longer end of its window. Check trichomes from day 56 but plan for day 65–70 as the realistic harvest target. Harvest at 20–30% amber — the full GDP body effect and grape terpene expression develop in the final week, so don't harvest early.

🔥 How does the potency compare to the photoperiod GDP?

~18–22% THC for the auto versus 20–27% for the photoperiod. This is a real and noticeable difference, particularly for users seeking GDP for serious therapeutic applications — chronic pain, insomnia, or anxiety where the deeper sedative effect of the full-potency photoperiod matters. The auto is a solid and effective indica, but for maximum therapeutic depth the GDP Feminised photoperiod is the right choice.

🌈 Will the buds turn purple like the photoperiod GDP?

Yes, with cool nights. The anthocyanin genetics are fully present in the auto version — temperature triggers them the same way. Drop nights to 15–18°C for the final 2–3 weeks and the purple develops naturally. For outdoor grows, a January planting targeting a late March/April harvest aligns with natural Australian cool nights for maximum expression. Summer harvests produce quality buds with good potency but less colour development without the cool nights.

🌱 Is Auto GDP easy to grow?

Intermediate — not beginner-friendly despite the autoflower format. The GDP genetics carry moderate nutrient sensitivity, and the fixed timeline means mistakes in the first three weeks follow through to harvest. A robust ruderalis-dominant auto is more forgiving. The main areas requiring attention are: starting in the final container (no transplanting), light feeding in weeks 1–3, airflow management in the dense bushy canopy from week 5 onward, and harvest timing (don't cut early). Growers with one or two successful auto runs under their belt will do well with this strain.

🪴 Can I transplant Auto GDP?

No. Germinate directly into the final container — 10–15 L indoors, 15–20 L outdoors. Transplanting causes stress during the fixed timeline the plant cannot recover from. Plan the container before the seed goes in.

🌾 What yields can I expect?

Up to 400 g/m² indoors under good lighting with LST. Outdoor plants produce 80–120 g each. These are realistic figures — not inflated. The compact size limits total production per plant, but the 63–70 day timeline allows 5–6 indoor runs annually and up to 3 outdoor runs per season, which changes the per-year yield equation significantly.

🌤 When should I plant Auto GDP outdoors in Australia for maximum purple expression?

December or January for a late March/April harvest — when natural night temperatures drop to 15–18°C across most Australian states. This timing aligns the harvest window with cool autumn nights that trigger maximum anthocyanin production naturally. September plantings (November/December harvest) produce quality buds with good potency but less colour development in the warmer summer temperatures.

🍇 Does Auto GDP taste like the photoperiod?

With a proper cure — yes, recognisably. The sweet grape and berry terpene characteristics carry through the Ruderalis cross with a proper 7–10 day flush and 3–4 week cure in sealed jars. Fresh-dried material doesn't represent the genetics well. The cure is non-negotiable for GDP terpene expression in any format.

🧪 What training works best?

LST only — low-stress training by tying down the main stem and lateral branches from week 2–3. The bushy GDP structure means there are more productive bud sites to expose than with single-cola auto genetics, so LST returns better yield improvement with this strain than with simpler autos. Topping is not recommended — the recovery time on the fixed auto timeline doesn't produce a net yield benefit.

💧 How should I feed Auto GDP?

Start at 1/4 strength for weeks 1–3 — this is more conservative than many autos but the GDP genetics warrant it. Build to 1/2 strength by week 3, transition to bloom nutrients when pre-flowers appear. Keep EC below 1.6 throughout flower. Back off nitrogen firmly from week 6. Flush with plain pH-adjusted water for 7–10 days before harvest. The grape terpene profile benefits noticeably from a clean finish.