Autoflowering seeds
by Azarius
Granddaddy Purple Auto is an indica-dominant autoflowering cannabis seed strain that delivers deep physical relaxation and a rich berry-hash flavour profile in as little as 8–9 weeks from germination. Born from the cross of Purple Urkle, Big Bud, and ruderalis genetics, this 70% indica produces dense, resinous buds with 16–19% THC — strong enough to satisfy experienced smokers, approachable enough if you're still finding your sweet spot.
Granddaddy Purple Auto seeds come in packs of 1, 3, 5, or 10. For a single indoor grow in an 80x80 tent, 3 seeds gives you a comfortable run with room for one dud. Running a full 120x120 space or growing outdoors? Grab the 10-pack — you'll use them across two or three cycles, and the per-seed cost drops noticeably. If you just want to test the genetics before committing, the single seed gets you there without the spend.
The original Granddaddy Purple photoperiod has been a fan favourite for over two decades — that grape-candy smell is unmistakable. This autoflowering version keeps everything people love about GDP and strips away the fuss. No light schedule changes, no sexing, no waiting 4+ months. You plant it, keep it fed and watered, and roughly 8–9 weeks later you're trimming sticky purple buds that smell like berry jam stirred through hash.
We'd pick this over most other purple autos for one reason: it actually delivers on yield. A lot of "compact autos" give you 150–200 grams per square metre and call it a day. Granddaddy Purple Auto pushes up to 400–550 g/m² indoors when you dial in the environment. Outdoors, expect up to 300 g per plant — solid numbers for a strain that tops out around 120 cm. It doesn't need a massive vertical space, which makes it a good fit for tents, balconies, and smaller gardens.
The one honest limitation: the 16–19% THC range means this isn't the hardest hitter on the shelf. If you're chasing 25%+ monsters, something like a Gorilla Glue auto will get you there. But GDP Auto isn't trying to floor you — it's the strain you reach for when you want to melt into the sofa with a film and actually enjoy the ride rather than stare at the ceiling wondering if time still works.
Granddaddy Purple Auto produces buds with a layered flavour that opens on sweet berry — think ripe blackcurrant — then shifts into a deeper, earthy hash note on the exhale. There's a subtle grape sweetness underneath that lingers. The aroma while growing is noticeable from about week 5 onward: fruity and dank, with that classic purple-strain sweetness that fills a room. According to research on cannabis terpene profiling, dried flowers from indica-dominant strains like GDP tend to show elevated levels of myrcene and linalool, which contribute to those berry-floral-hash characteristics (PMC11622677).
When you crack open a cured bud, the nose is immediately recognisable — sweet, slightly musky, with a sharpness that tells you the resin production did its job. The smoke is smooth for an indica, not harsh or cough-inducing, which makes it a good strain to share with friends who aren't used to heavy smoke.
Granddaddy Purple Auto is one of the more forgiving autoflowers to cultivate. The ruderalis genetics mean it flowers automatically regardless of light cycle, so you can run it under 18/6 or 20/4 from seed to harvest without switching to 12/12. Plants stay compact — around 100–120 cm — and develop a classic indica structure: bushy, with a dominant central cola and dense side branches.
One grower reported pulling 140g of dry bud from a single Granddaddy Purple plant after 9 weeks of veg and 10 weeks of flowering, describing the taste as fruity and sour with a strong relaxing effect. Your results will depend on your setup, but the genetics are solid — this strain doesn't ask for much and rewards decent care generously.
| Specification | Detail |
|---|---|
| Genetics | Purple Urkle x Big Bud x Ruderalis |
| Strain Type | 70% Indica / 30% Ruderalis |
| Flowering Type | Autoflowering |
| Seed to Harvest | 8–9 weeks |
| THC Content | 16–19% |
| Indoor Yield | 400–550 g/m² |
| Outdoor Yield | Up to 300 g/plant |
| Plant Height | 100–120 cm |
| Flavour Profile | Berry, hashish, sweet grape |
| Available Pack Sizes | 1, 3, 5, or 10 seeds |
If you're deciding between purple autoflowers, here's how GDP Auto stacks up against two popular alternatives in the catalogue.
| Strain | THC | Seed to Harvest | Indoor Yield | Dominant Effect |
|---|---|---|---|---|
| Granddaddy Purple Auto | 16–19% | 8–9 weeks | 400–550 g/m² | Deep relaxation, body-focused |
| Purple Punch Auto | 18–22% | 9–10 weeks | 350–450 g/m² | Sedating, couch-lock |
| Blackberry Auto | 15–20% | 8–10 weeks | 300–400 g/m² | Balanced, mellow |
GDP Auto wins on yield and speed. Purple Punch hits harder but takes longer and gives you less per square metre. Blackberry Auto is a solid all-rounder but doesn't quite match GDP's production. If you want the best balance of flavour, yield, and a manageable grow cycle, Granddaddy Purple Auto is the one we'd point you toward.
Running Granddaddy Purple Auto indoors? Pair it with a complete grow tent kit — tent, light, ventilation, and carbon filter in one box. The carbon filter is non-negotiable with this strain; the berry-hash aroma gets loud from week 5 onward. If you're growing in soil, grab a bag of BioBizz All-Mix — it's pre-fertilised for the first few weeks, which suits autos that don't want heavy feeding early on.
Granddaddy Purple Auto delivers a heavy-body, physically relaxing effect that builds gradually over 15–20 minutes. The initial onset brings a warm, settled feeling behind the eyes that spreads downward — shoulders drop, jaw unclenches, legs get heavy. Mentally, there's a gentle uplift that keeps things pleasant without racing thoughts. At 16–19% THC, it's strong enough to notice but unlikely to overwhelm anyone with moderate tolerance.
According to Healthline's review of indica strains, Granddaddy Purple is commonly associated with relaxation and is often chosen by those looking to de-stress (Healthline, "12 Indica Strains for Sleep, Pain Relief, Appetite"). Research on responsible cannabis use suggests that moderation of quantity and frequency, combined with appropriate settings, contributes to more positive outcomes (PMC4499492). Start with a small amount — a single joint or a half-bowl — and give it 20 minutes before deciding if you want more.
Common side effects reported with GDP include dry mouth and dry eyes. Keep water nearby. These are typical for indica-dominant strains and not specific to this cultivar.
We've been shipping cannabis seeds from Amsterdam since 1999, and purple strains have never gone out of fashion. Granddaddy Purple in particular has a loyal following — customers come back for it specifically because the flavour is consistent and the grow is predictable. The autoflower version made it accessible to people growing on balconies or in small flats where a photoperiod grow just isn't practical.
The most common question we get about GDP Auto: "Will it actually turn purple?" Usually, yes. The genetics carry strong anthocyanin expression, especially if you can drop night temperatures below 18°C in the final two weeks. But even plants that stay green produce the same berry-hash flavour and relaxing effect — the colour is cosmetic, not chemical.
Most plants are harvest-ready in 8–9 weeks from germination. Some phenotypes stretch to 10 weeks, but that's uncommon. The autoflowering genetics mean there's no separate veg and bloom phase — the plant transitions on its own around week 3–4.
Indoor yields range from 400–550 g/m² depending on your light, pot size, and feeding schedule. In a well-dialled 80x80 tent with a decent LED, 450 g/m² is a realistic target. Outdoors, expect up to 300 g per plant in a sunny spot.
Yes. It's one of the more forgiving autos available. No light schedule changes needed, compact enough for small spaces, and resistant to common beginner mistakes like slight overwatering. The 8–9 week turnaround also means you're not waiting months to see results.
Most plants show purple colouration, especially with cooler night temperatures in the final weeks. It's genetic — the Purple Urkle parent carries strong anthocyanin expression. Some phenotypes stay green, but the flavour and effect are the same regardless of colour.
Rich berry and grape on the inhale, shifting to an earthy hash flavour on the exhale. There's a lingering sweetness that's distinctly GDP. The smoke is smooth and not harsh, even for those who don't smoke regularly.
Dry mouth and dry eyes are the most commonly reported side effects. Keep water handy. At 16–19% THC, it's moderate in strength — unlikely to cause anxiety or paranoia at sensible doses, but start small if you're new to indica strains.
Absolutely. Plants stay around 100–120 cm tall, making them discreet for balconies and gardens. They handle temperature fluctuations well and don't need supplemental lighting. Expect up to 300 g per plant in a decent outdoor spot with 5+ hours of direct sun.
Last updated: April 2026
Medical disclaimer. This content is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare provider before use of any substance.
