F1 vs F2 vs S1 Cannabis Seeds Explained (Simple Guide)
Quick answer: F1 seeds are the first cross of two different stable parents, giving vigorous, uniform plants (hybrid vigour). F2 seeds come from crossing two F1s and show much more variation as traits segregate. S1 seeds are ‘selfed’, made by pollinating a plant with itself, so they closely resemble that single parent and are usually feminized. In short: F1 for uniformity and vigour, F2 for variation to select from, S1 to preserve one plant’s traits.
If you have browsed seed listings, you have seen labels like F1, F2 and S1, and they are not just jargon: they tell you how a seed was bred and what to expect from the plants. Understanding them helps you choose seeds that match your goal, whether that is uniform, vigorous plants, a pool of variation to hunt through, or a faithful copy of a favourite plant.
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THC | 30% - 37% (High) |
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Type | Feminized |
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Phenotype | 50% Indica / 50% Sativa |
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THC | 19% - 23% (Medium) |
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Type | Feminized F1 |
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Yield | High |
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Phenotype | 50% Indica / 50% Sativa |
The terms come from basic plant genetics (filial and selfed generations), applied to cannabis. Below we explain what F1, F2 and S1 mean, how they differ in stability and uniformity, and which makes sense for different growers, with a quick comparison table to keep it clear.
| Seed type | What it is | Key trait |
|---|---|---|
| F1 | First cross of two different stable parents | Vigorous and uniform (hybrid vigour) |
| F2 | Offspring of two F1 plants | More variation; traits segregate |
| S1 | Self-pollinated from a single plant (selfed) | Close to the parent; usually feminized |
F1 and F2 Seeds: Hybrid Vigour and Variation
F1 (first filial) seeds are the first-generation cross between two different, stable parent lines. Thanks to ‘hybrid vigour’, F1 plants tend to be vigorous, uniform and predictable, which is why commercial F1 hybrids are prized: grow a pack and the plants look and perform similarly. That consistency makes F1 a safe choice for most growers who want reliable results.
F2 seeds are the next generation, made by crossing two F1 plants. Here the parents’ traits start to segregate, so F2 plants show much more variation, a range of heights, flavours, structures and effects within the same batch. That unpredictability is a downside if you want uniformity, but it is exactly what breeders want when ‘phenotype hunting’ for new standout plants to develop.
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S1 Seeds: Selfing and Preserving a Plant
S1 seeds are made by ‘selfing’, inducing a single plant to produce pollen and using it to pollinate itself. Because there is only one parent, S1 offspring closely resemble that plant, which is how growers preserve or reproduce a particular favourite (for example a special clone) in seed form. S1 seeds are also usually feminized, since a female selfed with itself yields female seeds.
Are S1 seeds stable and good? They can be very good for faithfully capturing one plant’s traits, but ‘stable’ depends on the parent and the breeder’s skill, selfing can also surface recessive traits, so quality varies. For most growers wanting a copy of a prized plant, S1 is the tool; for brand-new hybrids, F1/F2 breeding is the route. To go deeper into making your own seeds, see our guides on cannabis pollen banking and feminized seeds.
Which Should You Choose?
For most growers, F1 seeds are the easy, reliable pick: uniform, vigorous plants with predictable results, ideal if you want a consistent grow. Choose F2 (or later generations) only if you enjoy variation and want to phenotype-hunt for something special, accepting that plants will differ. Pick S1 when your goal is to reproduce a specific plant’s traits as closely as possible, often in feminized form.
In short, match the seed type to your goal rather than assuming one is ‘better’. Newer, stabilised genetics are increasingly released as triploid lines too, which change the fertility picture, see our guide on triploid cannabis seeds for that emerging option. Whatever you choose, buying from reputable breeders matters most for getting what the label promises.
Why Seed Generation Matters for Your Grow
Knowing the generation helps you set expectations before you even germinate. If you buy F1 seeds, plan for a uniform crop, plants of similar height, timing and quality, which makes a grow easier to manage and harvest together. If you buy F2 or later, expect variation and be ready to select the best plants (phenotype hunting), which is rewarding but less predictable.
With S1 seeds, expect plants close to the single parent they were selfed from, usually feminized, which is ideal when you specifically want that plant’s traits. Matching the generation to your goal, consistency, selection, or preservation, saves disappointment and helps you choose seeds that suit your space, experience and aims. As always, reputable breeders are the best guarantee the label reflects reality.
FAQs about F1, F2, and S1 Seeds
What are S1 cannabis seeds?
S1 seeds are ‘selfed’ seeds, made by inducing a single plant to pollinate itself, so the offspring closely resemble that one parent and are usually feminized. Growers use S1 seeds to preserve or reproduce a favourite plant (like a special clone) in seed form. Stability depends on the parent and the breeder’s skill.
What is the difference between S1 and F1 seeds?
F1 seeds are the first cross of two different stable parents, giving vigorous, uniform plants (hybrid vigour). S1 seeds come from one plant pollinating itself, so they closely copy that single parent and are usually feminized. F1 is about combining two lines; S1 is about preserving one plant’s traits.
Are S1 seeds stable and good?
They can be, especially for faithfully reproducing a prized plant, but stability depends on the parent plant and the breeder’s skill, since selfing can surface recessive traits. Good S1 seeds from a careful breeder are reliable; poorly made ones vary more. For brand-new hybrids, F1 seeds offer more vigour and uniformity. Buy from reputable breeders.
Are F1 or S1 seeds better?
Neither is universally better; it depends on your goal. F1 seeds give vigorous, uniform plants, ideal for a consistent, easy grow. S1 seeds closely reproduce a single favourite plant, usually in feminized form, ideal for preserving specific traits. Choose F1 for reliability and vigour, S1 to copy a prized plant. Buy from reputable breeders either way.
