Guava Runtz Auto unites two decorated autoflower lines in one F1 hybrid. On one side is Fast Buds’ own Guava Auto RF3, a fully stabilized line that Fast Buds reports as the champion of the latest Autoflower World Cup. On the other is Mango Runtz F5 Auto from Mephisto Genetics, a multi-award winner valued for its terps and its short, tidy build.
Fast Buds lists it in its Champions Line, built from 2025 cup-winning genetics. The idea was simple: stack elite performance and terpene expression into a single plant. Early testing shows strong hybrid vigor, with the tidy shape of Mango Runtz boosted by the power, fresh vigor, and fast growth of Guava RF3.
Plants reach 70-120 cm (28-47 in) in the XL size class and finish from seed in 8-9 weeks (about 56-63 days) under 18/6 or 20/4, with no light switch required. Fast Buds rates yields at 450-600 g/m² (1.6-2 oz/ft²) indoors and 60-300 g (2.4-9.5 oz) per plant outdoors.
The genetic balance sits at an even 50% Sativa / 50% Indica.
Two Phenotypes, One Loud Terpene Profile
The line expresses two main phenotypes. One darkens to a deep, almost black coloration; the other stays greener, with darker shades creeping in during the final weeks. Both carry nearly identical terpenes, pack their buds tightly, and grow with a uniform shape from plant to plant.
The smell is bold and upfront: tropical fruit and sugary candy over a deep, layered base. Those notes hold up from fresh flower through the cure and into extracts, and the buds carry serious bag appeal.
Growers describe an uplifted, happy, creative effect, with an energetic, talkative edge that suits daytime sessions and time with friends.
Growing Guava Runtz Auto
With its compact Mango Runtz build and the vigor of Guava RF3, this hybrid is straightforward to manage in a tent. A light LST session evens out the canopy, and a carbon filter is worth running once the candy-fruit aroma kicks in during bloom.
Guava Runtz Auto Characteristics
| Strain type | Autoflowering (feminized) |
| Genetics | Guava Auto RF3 x Mango Runtz F5 Auto (Mephisto Genetics) |
| Generation | F1 hybrid feminized autoflower |
| Indica/Sativa | 50% Indica / 50% Sativa |
| THC | Up to 30% |
| CBD | Less than 1% |
| Effect | Uplifted, happy, creative |
| Flavor | Tropical fruit, guava, sweet candy |
| Indoor yield | 450-600 g/m² (1.6-2 oz/ft²) |
| Outdoor yield | 60-300 g/plant (2.4-9.5 oz/plant) |
| Seed to harvest | 8-9 weeks (56-63 days) |
| Height | 70-120 cm (28-47 in) |
| Size class | XL |
| Grow setting | Indoor, outdoor, greenhouse, mixed light |
| Best cultivation technique | Light LST, carbon filter, 18/6 or 20/4 light |
FAQ
What are the parents of Guava Runtz Auto?
It is an F1 cross of Fast Buds’ Guava Auto RF3 and Mango Runtz F5 Auto from Mephisto Genetics.
Why is it part of the Champions Line?
Both parents are award winners. Fast Buds reports Guava Auto RF3 as champion of the latest Autoflower World Cup, and Mango Runtz is a multi-award winner, so the cross is built from 2025 cup-winning genetics.
What phenotypes does Guava Runtz Auto show?
Two main types: one turns deep, almost black, while the other stays greener with darker shades late in bloom. Both have very similar terpenes and dense buds.
How strong is Guava Runtz Auto?
Fast Buds lists THC levels of up to 30%, with CBD under 1%.
How long does Guava Runtz Auto take from seed to harvest?
About 8-9 weeks (56-63 days), with no light-schedule change.
What yield can I expect?
Indoors, Fast Buds lists 450-600 g/m² (1.6-2 oz/ft²). Outdoors, plants yield about 60-300 g (2.4-9.5 oz) each.
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