Grandaddy Purple Auto Seeds

Granddaddy Purple Auto: Fast Grape Candy in 9–10 Weeks

If you’re looking to buy Granddaddy Purple Auto seeds in Australia, here’s your shortcut to deep colour and grape-berry terps—without the photoperiod fuss. This compact, stealth-friendly auto keeps the classic GDP vibe but sprints from seed to sticky harvest in a single school term. Plant, guide, and let her sing.

Quick Stats

Indica-leaning autoflower (~65/35) with THC ~19–23% and CBD <1%; finishes in ~9–10 weeks from seed; height ~70–110 cm; yields ~450–550 g/m² indoors or ~90–160 g/plant outdoors; terp profile is classic grape, berry, sweet candy; Aussie outdoor timing in warm zones typically lands late Feb–late Mar (cooler zones: Mar–early Apr). Matty’s Take: “Purple vibes, candy terps, and no waiting around—GDP with a fast-forward button.”

The Legend: Purple Royalty, Auto Mode

Granddaddy Purple wrote the book on grape-berry terps. This auto version keeps that signature flavour and colour lineage (Mendo Purps × Skunk × Afghan in the background), then weaves in Ruderalis so it flowers on its own. The result? Classic GDP character without chasing light schedules. The purple isn’t just for show—it’s linked to anthocyanin production, often triggered by cooler nights.

Matty’s Take: “Same candy cupboard, smaller footprint, faster finish. It’s GDP you can grow on a lunch break.”

Flavour & Aroma: Grape Soda & Berry Chew

On the nose: Sweet grape soda, crushed berries, light floral candy. On the tongue: Sugary berry chew with a smooth, earthy-floral exhale. Room note: Clean candy sweetness—easy to love, hard to hide.

Matty: “Tastes how it smells—no weird afters. Keep your dry room cool to lock the sweets in.”

Effects & What to Expect

• First wave — Gentle head-lift and mood glow; colours pop, shoulders drop.
• Then it settles — Smooth, body-heavy calm with a clear lane to keep pottering about.
• Final vibe — Unwound and cheerful; ideal for late arvo into evening.

Dial dosage for day–to–evening—lighter tokes for socials and chores, fuller bowls for couch-and-playlist.

How I Grow Granddaddy Purple Auto (Matty’s Way)

Skill level: Beginner–Intermediate. Forgiving, but autos demand timing discipline.

• Container: Start in final pot. Soil 11–18 L (3–5 gal); coco 7–11 L (2–3 gal) with frequent fertigation.
• Training: LST only—tie and bend from day 18–28. No topping, no HST.
• Stretch: ~25–35% after pre-flower. Keep canopy even; avoid hard defol.
• Schedule: 18/6 throughout. Stable DLI beats chasing 24/0.
• Outdoor AU: Best in warm coastal QLD/NSW/WA; target an early March chop to beat late humidity.

Matty’s pH & Feeding Notes

• pH Target (Soil/Coco): 6.4 (range 6.3–6.5) mid-bloom for optimal P/K uptake. Hydro 5.8–6.1.
• EC: 0.9–1.1 seedling → 1.2–1.4 early flower → peak 1.5–1.6 (auto = light-moderate feeder)
• PPFD: ~700–800 µmol mid-bloom (raise slowly from ~500 at Week 3)
• VPD: 0.9–1.1 kPa early → 1.1–1.3 kPa bloom; RH ~45–55% flower → ~40–45% late
• Colour Assist: Cooler nights (18–20 °C) from Week 7 help the purple show—don’t force if RH is risky.

Matty: “Feed clean and a touch lean. Push EC like a hero and she’ll sulk like a teen with no Wi-Fi.”

Matty’s Grow Log: Inside the Tent

Phase / Week	Key Action / Status	Matty’s Tip
Week 1 (Seedling)	Sprout in final pot; gentle light, warm & humid.	Don’t drown it—water in rings so roots chase moisture.
Week 2–3 (Juvenile)	Rooting hard; first LST anchors.	Your only proper training window—bend, don’t break.
Week 4 (Pre-flower)	Pistils show; raise PPFD, steady feed.	No topping “just to try it”. Autos don’t have recovery time.
Week 6–7 (Mid Bloom)	Stacking starts; terps ramp.	Fresh air in, stale air out—keep RH < 50% to dodge Botrytis.
Week 8–9 (Late Bloom)	Bulk & ripen; consider cooler nights.	Ease N, keep P/K available; watch trichs go cloudy.
Week 9–10 (Harvest)	Cloudy with 10–20% amber; chop & hang 18–20 °C.	Slow dry = loud candy terps. Don’t rush the cure.

RED FLAG: The Week 2 Yield Killer 🚨

Transplant shock at Week 2 is a permanent yield cap. If you up-potted an autoflower, accept the loss and finish light—next time, start in the final pot. Autos don’t have time to recover from drama.

Matty: “If you’ve already transplanted, don’t compound it. Gentle LST, lean feeds, and let her coast.”

Matty’s Advanced Notes (For the Nerds)

• Terpenes: Myrcene (soothe), Caryophyllene (spice/body), Pinene (lift). Cooler dry/cure preserves grape esters.
• Training: Autos = LST only. Begin gentle bends days 18–28; avoid topping and heavy defol—no recovery runway.
• Lighting: Keep PPFD 700–800 µmol·m⁻²·s⁻¹ in bloom; avoid daily DLI swings > 10%. Gradual ramp beats blast and burn.
• Climate: Ideal 24–28 °C day / 18–20 °C night with 5–8 °C drop to trigger colour safely.
• Air Management: High CFM across canopy; avoid dead zones in dense mid-bloom. Carbon filter one tier above tent volume.
• Irrigation: Coco: little-and-often (10–20% runoff). Soil: allow light dryback—autos hate wet feet.
• Pests: Outdoors: caterpillars near harvest—run BT weekly from early bloom. Indoors: watch for broad mites in humid microclimates; scout undersides with a loupe.

Mythbusting

Myth: Autos can’t get potent. 💪
Truth (Matty): With proper PPFD and clean feeds, GDP Auto comfortably hits ~20% THC.

Myth: More darkness = more flowers on autos. 🌗
Truth (Matty): Time-based, not light-triggered. Stable 18/6 wins.

Myth: You must top all plants for yield. ✂️
Truth (Matty): Not autos—LST is the cheat code; topping costs time you don’t have.

Myth: Purple = stronger. 🍇
Truth (Matty): Colour is anthocyanins, not THC. Pretty ≠ punchy—GDP just happens to do both.

Matty’s Real-World Example: The Balcony Batch

Last season, my mate Dave in Newcastle ran three GDP Autos on his apartment balcony, aiming for stealth. He sowed in 20L fabric pots in early December. Instead of chasing high-end nutrients, he used a slow-release organic soil. The biggest issue? Rainfall. Autos hate surprise water. Dave put them on dollies and moved them under cover during every big storm.

Because Newcastle has warm nights, the colour didn’t show until Week 8, but the flavour still locked in. He harvested at Day 65 and pulled a solid 120g per plant. The lesson: Autos prioritise speed over perfection. Control the water and the roots, and the plant will deliver, even if you can’t guarantee a purple finish.

Who It’s For?

Perfect If You:

• Want GDP flavour fast (seed–jar in ~10–12 weeks including dry/cure).
• Grow in tight spaces or on balconies and need stealth height.
• Prefer simple runs: final pot, 18/6, gentle LST.
• Like sweet, fruity terps over fuel & musk.

Maybe Not For You If You:

• Insist on topping or heavy HST every run.
• Routinely overwater seedlings or chase max EC.
• Need 150 cm+ trees or outdoor monsters.

Matty’s Final Word

GDP Auto is the no-dramas path to purple candy—compact, cooperative, and quick. Treat her gentle, keep the air clean, and you’ll pull jars that smell like a corner-store lolly aisle. Cheers to fast, sweet wins. 🍇

Ready to Grow?

Grab Granddaddy Purple Auto or browse all Autoflower Seeds, then check our Germination Guide and Humidity & VPD Guide.

Matty’s Quick-Fire Q&A