Granddaddy Purple Strain Review: THC, Effects, Flowering Time & Yield

Granddaddy Purple — GDP — is the purple indica everyone pictures when they think of purple weed: a Purple Urkle × Big Bud cross with 25% THC, a grape-and-berry flavour, dense resinous buds and a heavy, relaxing high, on a plant that is easy to grow and finishes in October. This Granddaddy Purple strain review covers its genetics, THC, effects, flowering time and yield — and, because it is the question we get most, what it really takes to get the purple colour, straight from growers on our product page.

Granddaddy Purple strain at a glance

What is Granddaddy Purple?

Granddaddy Purple was introduced by breeder Ken Estes in the San Francisco Bay Area in 2003, a cross of Purple Urkle and Big Bud. Purple Urkle brought the grape flavour and the colour; Big Bud brought size and yield. It quickly became the reference purple strain of the medical era and is still one of the most searched indicas in North America.

Our Granddaddy Purple feminized seeds are our own cut of that lineage, selected for potency, resin and ease of growing. Strain names are not protected, so GDP from another seed bank is a different plant; everything on this page describes ours. Want the same genetics on a shorter timeline? See Granddaddy Purple Autoflower.

Is Granddaddy Purple indica or sativa?

Granddaddy Purple is mostly indica, roughly 70/30, and grows like one: a compact, bushy plant with a thick main cola, tight internodes and a modest stretch. The effect is indica too — a brief euphoric lift, then a heavy, body-centred relaxation that makes it an evening strain. For a purple strain with more daytime energy, look at our sativa-leaning Blue Dream.

Smell and flavour: grape, berry and a peppery finish

The aroma is grape and berry with sweet, earthy undertones — one Ontario grower described a “sour apple grape smell”, another “skunky grapes”. On the palate it is fruity and sweet with a peppery note on the finish that a Quebec grower picked out: “the taste is fruity and peppery, sublime.” It is one of the most distinctive flavours in our catalogue.

Appearance: dense, resin-coated buds — purple when conditions allow

GDP buds are dense and heavy, covered in trichomes by week seven — “just covered in trichomes”, as one grower put it — with orange pistils against green and, under the right conditions, deep purple. Honest note: the purple is not guaranteed. It depends on the phenotype, on cool night temperatures late in flower and on keeping nitrogen down. Some growers get stunning purple, red and orange colas; others get a great green harvest with “beautiful fall colours” and no purple at all. More on that below.

Granddaddy Purple effects

The effect starts with a euphoric buzz that lifts the mood, then settles into deep, heavy relaxation in the body. At 25% THC it is strong, and it is an evening strain: good for unwinding, sleep and taking the edge off a long day. Customers describe a “nice rich smoke” and recommend it “10/10”. Effects vary with the person, the dose and how the plant was grown.

How strong is Granddaddy Purple? THC content

Granddaddy Purple delivers about 25% THC with very little CBD, depending on the growing conditions, the phenotype and the harvest window. That makes it one of the strongest indicas we sell. For a gentler indica with a similar ease of growing, Northern Lights at 15%+ is a good alternative.

Growing Granddaddy Purple: flowering time and yield

Granddaddy Purple is rated easy. It resists many common pests and diseases, does not need much training and stays a manageable size. Indoors it flowers in 65 to 70 days and typically gives 450 to 500 g/m²; growers on our product page report far more from well-run setups, including 536 g from a single plant under a 1500 W LED. Outdoors it is typically ready in October, with 600 to 700 g per plant in good conditions — one Quebec grower harvested 1,300 g from two plants. Those figures are ranges, not promises. To bring out the purple: keep night temperatures in the low teens (°C) during the last two to three weeks of flower, go easy on nitrogen in bloom, and accept that some phenotypes simply stay green. The dense buds want airflow in a wet fall.

Indoor is measured per m², outdoor per plant — the two figures aren’t directly comparable. Real grower results vary widely.

What growers report

We would rather give you the whole picture, so here is what customers wrote on the Granddaddy Purple product page (15 reviews, rated 4.4 out of 5 at the time of writing).

• Yields: “536 g from one plant indoors under 1500 W LED” with “big, fat purple, red and orange colas”; “2 plants, 1,300 g” from a Quebec grower; “very satisfied, fruity and sweet, true to itself”.
• Resin and smell: “these beauties are amazing, they are just covered in trichomes and smell kinda like skunky grapes” at week 7; “excellent sour apple grape smell, nice rich smoke and beautiful fall colours, very nice trichome production”.
• The purple question: two reviewers gave low ratings because their plants did not turn purple after 10 weeks. Two other growers answered them, and we agree: “if you have too much nitrogen in your grow you get no purple; also it depends on phenotypes… dropping temps in the low 60s (°F) at night helps bring out purples. It takes work and a bit of luck.” Colour is a bonus, not the point — the potency and flavour are the same either way.
• Service: several Quebec customers mention orders arriving in 3 to 4 days with free bonus seeds.

The takeaway: GDP is an easy, heavy-yielding, very strong indica. Grow it for the grape flavour and the potency; treat the purple as a bonus you can encourage with cool nights and light feeding.

Is Granddaddy Purple right for you?

If you want a strong, easy, grape-flavoured indica for evenings, with heavy yields and a plant that handles a Canadian fall, Granddaddy Purple is a great pick — and one of our featured strains. If purple colour is the priority, grow it with cool September nights outdoors or drop your night temperature indoors in the last weeks, and consider popping several seeds to find a purple phenotype.

Granddaddy Purple: frequently asked questions

Shop Granddaddy Purple feminized seeds →