Grapefruit Auto

Grapefruit Auto Cannabis Seeds by FastBuds

Grapefruit Auto is an autoflowering feminised cannabis seed that delivers indoor yields of 400–600g/m² in just 8–9 weeks from germination — numbers that would make most photoperiod strains nervous. Bred by FastBuds from a Sour Citrus phenotype clone sourced in Vancouver, this compact plant packs 19% THC and 1% CBD into dense, resinous buds that smell like someone zested a grapefruit into a bag of sour sweets. If you want a fast, low-maintenance grow with a genuinely impressive end product, this is where you start.

Why Grapefruit Auto Seeds Deserve Your Grow Space

We've sold a lot of autoflowering seeds over the years, and the gap between autos and photoperiod strains has been closing fast. Grapefruit Auto is one of those varieties that makes you forget you're growing a Ruderalis crossing at all. The FastBuds team used a specific Sour Citrus phenotype clone from Vancouver as the genetic backbone — not just a vague "citrus lineage" but a selected, proven cut — and crossed it into their autoflowering line to create something genuinely special.

The result is a plant that stays between 90 and 120cm tall, finishes in 8–9 weeks from the moment the seed cracks open, and still manages to fill out with the kind of dense, trichome-coated buds you'd expect from a much longer grow cycle. Indoors under proper lighting, 400–600g/m² is realistic — not a best-case fantasy printed on the packet. Outdoors, individual plants can carry up to 300 grams each by harvest time.

The honest limitation? At 90–120cm, she's not going to fill a tall grow tent the way a stretchy sativa would. If you're running a SOG or working with limited vertical space, that's actually a benefit. But if you like towering plants with massive internodal spacing, this isn't your girl. She grows compact, bushy, and dense — which is exactly what most indoor growers want.

Aroma, Flavour, and Effects of Grapefruit Auto

This is where Grapefruit Auto really earns its name. Crack open a cured bud and you get hit with a sour, citrusy smell — sharp grapefruit peel with a sweet undertone that rounds it out. It's not subtle. Your carbon filter will be earning its keep during the last few weeks of flower. When smoked, the flavour leans sweeter than the nose suggests — that sour citrus edge softens into something almost candy-like on the exhale.

At 19% THC and 1% CBD, the cannabinoid profile delivers a balanced effect: cerebral stimulation that keeps you engaged without racing thoughts, paired with a soothing body feel that takes the edge off without gluing you to the sofa. It's the kind of smoke that works in the afternoon without writing off your evening. Compared to something like a pure indica auto, you get more headspace and less sedation — a good middle ground.

Grapefruit Auto Grow Specifications

How to Grow Grapefruit Auto Seeds

Autoflowers are forgiving by nature, and Grapefruit Auto is no exception. That said, a few things will push your yield from "decent" toward that 600g/m² ceiling. Here's how we'd run it:

1. Germinate your seeds using the paper towel method or directly in a small pot of moist, airy substrate. Taproots typically appear within 24–72 hours.
2. Plant the germinated seed 1–2cm deep in its final container — autos don't love transplanting. A 15–20 litre fabric pot with a light, well-draining soil mix is the sweet spot.
3. Run your lights on an 18/6 schedule from day one through harvest. Autos don't need a light cycle change to trigger flowering — they'll do it on their own around week 3–4.
4. Keep feeding light during the vegetative phase. Autos are sensitive to overfeeding. Start at roughly 0.8ml of nutrients per litre of water and increase gradually as the plant demands it.
5. Once pre-flowers appear, switch to a bloom nutrient regime. Grapefruit Auto's compact structure means light penetration is usually good without heavy training, but gentle LST (low stress training) in the first 3 weeks can open up the canopy and boost lower bud sites.
6. Monitor humidity closely during weeks 6–8. Those dense, resinous buds are magnets for mould if relative humidity climbs above 50% in late flower.
7. Harvest when trichomes are mostly milky with a few turning amber — typically 8–9 weeks from germination. Dry slowly in a dark room at 18–20°C and 55–60% humidity for 7–10 days, then cure in glass jars for at least 2 weeks.

Grapefruit Auto vs Other FastBuds Autoflowers

If you're choosing between FastBuds varieties, here's how Grapefruit Auto stacks up against two other popular options in the catalogue:

Grapefruit Auto is the fastest finisher of the three and the best pick if you want a balanced, functional effect rather than full couch-lock. If raw potency is your priority, Gorilla Glue Auto hits harder at 24% THC — but it takes an extra week or two and leans much heavier on the body side.