How to Grow Granddaddy Purple Autoflower
Granddaddy Purple Auto is a colorful, heavy-bodied, indica-dominant autoflowering strain that crosses Purple Urkle and Big Bud with a ruderalis to make it flower on age. It is an 80/20 indica with a medium 16-19% THC, a sweet, berry and hashy flavor, and a focused, happy, relaxed effect. Compact, purple and resinous, it brings classic Granddaddy Purple character to a fast, easy auto grow.
As an autoflowering strain, Granddaddy Purple Auto flowers automatically with age rather than waiting on a change in the light cycle, so there is no need to switch it to shorter days. You simply give it long days from start to finish and it starts flowering on its own after a few weeks, running its whole life cycle in about 8 to 10 weeks from seed to harvest. That speed and simplicity are exactly what make autos so easy to grow.
Recommended Strains
Granddaddy Purple Auto
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THC | 16% - 19% (Medium) |
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Type | Autoflowering |
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Yield | High |
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Phenotype | 80% Indica / 20% Sativa |
Granddaddy Purple
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THC | 25% (High) |
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Type | Feminized |
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Yield | High |
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Phenotype | 70% Indica / 30% Sativa |
Sweet, frosty and famously purple, Granddaddy Purple Auto is a rewarding auto to grow whether you are new to it or experienced. You can see the full genetics and buy Granddaddy Purple Auto seeds on the strain page, and browse the rest of our autoflowering seeds alongside it.
Strain Profile at a Glance
| THC | Medium (16-19%) |
|---|---|
| Lineage | Purple Urkle x Big Bud x Ruderalis |
| Type | Autoflowering |
| Genetics | 80% Indica / 20% Sativa |
| Climate | Warm and dry |
| Life cycle | 8-10 weeks seed to harvest |
| Harvest (outdoor) | All season |
| Height | 3.94 ft / 1.2 m |
| Yield indoor | 1.31-1.8 oz/ft² (400-550 g/m²) |
| Yield outdoor | 10.58 oz/plant (300 g/plant) |
| Grow difficulty | Easy, beginner-friendly |
| Flavors | Berry, Hashish, Sweet |
| Effects | Focused, Happy, Relaxed |
Promos & Deals
Growing an Autoflowering Strain
Granddaddy Purple Auto flowers on its own schedule, starting to bloom a few weeks after it sprouts no matter how long the days are. That means you keep it under long light the whole way through, typically 18 hours on and 6 off, or even 20/4, from seedling right to harvest; there is no switch to a shorter day to trigger flowering. The trade-off is that you cannot delay flowering to grow the plant bigger first, so every week of healthy early growth counts.
Because autos grow fast and do not like having their roots disturbed, start Granddaddy Purple Auto in its final pot rather than transplanting it. Sow the seed straight into the container it will finish in, go easy on the feed while it is young, and let it establish without a check. With a short life cycle of around 8 to 10 weeks from seed to harvest, a smooth start is the single biggest thing you can do for a strong, even finish.
Climate and Where to Grow It
Granddaddy Purple Auto suits a warm, dry climate and, like most autos, it is flexible about when you plant it. Because it flowers on age rather than on the season, you can run it at almost any time where the weather is warm enough, which is why its harvest window is listed as all season; outdoors you can even fit in more than one cycle in a long, warm year. At a compact 1.2 m it slips easily into a tent or a sunny corner.
Yields are high for an auto: around 400-550 g/m² indoors in an optimized setup and about 300 g per plant outdoors on its short cycle. As a sturdy, forgiving indica it is easy to grow, so the main job is a smooth start and good light to build those dense, colorful colas.
Keep humidity sensible through flowering to protect those dense, resinous buds: around 55-60% early on, nearer 40% as the flowers fill out, and lower toward harvest. Its preference for a drier climate helps keep the tight colas clean, but steady airflow still matters. Aim for temperatures around 68-80°F (20-27°C), and let the nights cool a little late in flower to coax out the deep purple color this strain is famous for.
Feeding Schedule (EC Guide)
Granddaddy Purple Auto is a resinous, productive auto, but autos want a lighter hand than photoperiod plants, so keep the feed modest and build slowly. Start very light, raise it gently as the plant grows, push a little more phosphorus and potassium through flower, then flush at the end so the sweet, berry notes come through clean. The ranges below are a starting guide; adjust to your water and medium.
| Stage | EC (mS/cm) | Notes |
|---|---|---|
| Seedling | 0.4-0.6 | Very light feed while roots establish in the final pot |
| Early growth | 0.8-1.2 | Raise nitrogen gently as the plant builds size |
| Early flower | 1.2-1.4 | Shift toward bloom nutrients (P and K) |
| Full flower | 1.4-1.6 | Peak bloom feed while the buds swell |
| Flush | 0.0-0.4 | Plain water for the final 1-2 weeks |
Flowering and Harvest
Granddaddy Purple Auto starts flowering a few weeks from sprouting and runs its whole cycle in about 8 to 10 weeks from seed to harvest, with no change in the light cycle needed. It fills out with dense, resin-coated, trichome-frosted buds on a compact frame, often turning deep purple in a cool finish, developing a sweet, berry aroma with a rich, hashy undertone. Because it flowers on age, its harvest comes on a fixed, quick timeline.
Yields are high for an auto: around 400-550 g/m² indoors and about 300 g per plant outdoors on its short cycle. Keep the colas supported and the canopy open so the lower buds get light, feed it lightly through flower, and harvest when most of the trichomes have turned cloudy with a few amber for the fullest sweet-berry flavor and the most rounded effect.
Drying and Curing
Dry whole plants or branches in a dark room at around 60°F (15-18°C) and 55-60% humidity for 7-14 days, until the thin stems snap rather than bend. A slow, even dry matters with such dense, resinous buds, because they can stay damp in the middle while the outside dries, and a gentle dry protects both the sweet, berry aroma and the deep purple color.
Then cure the trimmed buds in sealed jars, burping them daily for the first week and letting them settle for three to four weeks. A proper cure is what brings out the sweet, berry and hashy notes and smooths the smoke, turning a freshly dried auto harvest into the rich, fruity, full-bodied result Granddaddy Purple is known for.
What to Do With Your Trim
Don’t bin the sugar leaves you remove while manicuring. Granddaddy Purple Auto is a very resinous, frosty plant, so its trim is excellent for dry sift, bubble hash or rosin. That heavy resin and sweet, berry aroma make the trim genuinely valuable, turning offcuts into a potent, flavorful concentrate run rather than waste.
Flavor and Terpenes
Granddaddy Purple Auto leads with a sweet, berry flavor over a rich, hashy base, the grape-and-berry character that made Purple Urkle and its Granddaddy Purple line famous, with the heavy body of Big Bud. It is a smooth, fruity smoke, and a good cure really brings that sweet-berry character forward in the jar and on the inhale.
Its terpene profile shapes that flavor. A fresh touch of alpha-pinene gives a clean, piney lift, while camphene adds an earthy, woody note and linalool brings a soft, floral quality that plays into the berry sweetness. This straightforward profile keeps the flavor sweet and fruity with a grounded, hashy depth underneath.
Effects and Best Use
With its medium 16-19% THC and strongly indica 80/20 make-up, Granddaddy Purple Auto delivers a gentle, body-leaning experience. It is reported as focused, happy and relaxed, pairing a clear, settled head with a comfortable body, which makes it a good strain for unwinding without feeling heavy. Its medium potency keeps it approachable and easy to dose.
That focused, happy, relaxed profile makes it an easygoing all-rounder, good for a mellow, productive afternoon or an easy evening while enjoying its sweet, berry flavor. The combination of a fast, compact, colorful auto grow, a comfortable balanced effect and a rich, fruity taste is exactly why this Granddaddy Purple autoflower stands out.
Common Problems and Pro Tips
Granddaddy Purple Auto is forgiving, but autos reward a careful start. Sow it straight into its final pot to avoid a transplant check, go light on the nutrients while it is young, and do any training early and gently, because once an auto starts flowering it will not recover lost time. Stick to low-stress training only, and only while the plant is still growing.
At a compact 1.2 m it is easy to manage, so the main jobs are a smooth start, good light and keeping the air moving around its dense, resinous colas. Its preference for a drier climate helps keep mold away, but still hold humidity sensible through flower and defoliate a few of the largest fan leaves so light reaches the lower buds. To bring out the deep purple color, let the nights cool a few degrees late in flower.
As a pro tip, make the most of its color and resin: let the late-flower nights run cool for the richest purple, keep the feed modest, and protect the terpenes with a proper plain-water flush and a full three to four week cure. Save the frosty trim for concentrates, and harvest when most trichomes are cloudy with a few amber for a rich, sweet-berry result.
FAQ
Is Granddaddy Purple Auto an autoflowering strain?
Yes. Granddaddy Purple Auto flowers automatically with age rather than on a change in the light cycle, so you keep it under long days, usually 18/6 or 20/4, from seedling to harvest. It starts flowering on its own a few weeks after sprouting and runs its whole life cycle in about 8 to 10 weeks from seed to harvest, which makes it fast and simple to grow.
Should I transplant Granddaddy Purple Auto?
No. Autos grow fast and do not like having their roots disturbed, so start Granddaddy Purple Auto straight in its final pot rather than transplanting it. Sow the seed into the container it will finish in, go easy on the feed while it is young, and let it establish without a check. A smooth, uninterrupted start is the single biggest thing you can do for a strong finish.
How do I get Granddaddy Purple Auto to turn purple?
The deep purple color comes out most strongly when the nights cool down a little late in flower. Let the temperature drop a few degrees after lights-off in the final couple of weeks and the buds and leaves tend to show richer purple tones. It is largely genetic, so it will color up anyway, but a cool finish brings out the best of it.
How long does Granddaddy Purple Auto take?
Granddaddy Purple Auto runs its whole life cycle in about 8 to 10 weeks from seed to harvest, because it flowers on age rather than on the season. That short, fixed timeline means you can plant it almost any time where it is warm enough, and outdoors you can fit more than one cycle into a long, warm year. There is no light-cycle change to manage.
What does Granddaddy Purple Auto taste like?
It has a sweet, berry flavor over a rich, hashy base, the grape-and-berry character of the Granddaddy Purple line. Alpha-pinene adds a fresh, piney lift, camphene an earthy, woody note, and linalool a soft floral quality. A proper three to four week cure really brings that sweet-berry character forward on the inhale.
How much does Granddaddy Purple Auto yield?
It is a high yielder for an auto, giving around 400-550 g/m² indoors in an optimized setup and about 300 g per plant outdoors on its short cycle. Give it a big enough final pot, plenty of light and good airflow, and this compact, colorful plant rewards you with a heavy, resinous harvest.
