# F1

> F1 is the first generation of offspring from crossing two parents; if the parents are inbred and different, F1 plants are uniform and often show hybrid vigour.

- Canonical: https://genetixbay.com/knowledge/glossary/f1.html
- Also written: F1 hybrid, first filial generation, F1 seed, F1 hybrid seed, F1s
- Glossary category: Genetics and breeding · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

F1 is the first filial generation: the seed of a cross between two P1 parents. In classic plant breeding the parents are two different [inbred lines](https://genetixbay.com/knowledge/glossary/inbred-line.md), so every F1 seed gets the same set of [alleles](https://genetixbay.com/knowledge/glossary/allele.md) from each parent. The result is a uniform, highly heterozygous crop that often shows [hybrid vigour](https://genetixbay.com/knowledge/glossary/heterosis.md).

## In practice

That uniformity is why maize and vegetable growers buy F1 hybrid seed every year. Cannabis is mostly different. Few cannabis parents are inbred, so a cross of two hybrid clones produces "F1" seed that varies a lot. Growers still call it F1 because it is the first cross, but genetically it [segregates](https://genetixbay.com/knowledge/glossary/segregation.md) more like an [F2](https://genetixbay.com/knowledge/glossary/f2.md).

True uniform cannabis F1 seed requires two inbred parents ([IBLs](https://genetixbay.com/knowledge/glossary/ibl.md) or highly inbred lines). It exists, but it is a significant breeding investment.

Saving seed from F1 plants and growing it out gives F2s, which segregate widely. That is expected, not a fault of the seed.

## Don't confuse with

- **F2**: offspring of F1 × F1. Wide variation.
- **Feminised F1**: an F1 made with [reversed female](https://genetixbay.com/knowledge/glossary/sex-reversal.md) pollen; still an F1, but with all-female seed.
- **Hybrid**: any cross between different parents. Every F1 is a hybrid; not every hybrid is a uniform F1.

## Myth check

"F1 hybrid" on a pack does not guarantee uniformity unless the parents were inbred; see [F1, F2, F3 explained](https://genetixbay.com/knowledge/breeding/f1-f2-f3-explained.md).

## Related terms

[P1](https://genetixbay.com/knowledge/glossary/p1.md), [F2](https://genetixbay.com/knowledge/glossary/f2.md), [Hybrid](https://genetixbay.com/knowledge/glossary/hybrid.md), [Heterosis](https://genetixbay.com/knowledge/glossary/heterosis.md), [Filial generation](https://genetixbay.com/knowledge/glossary/filial-generation.md), [Inbred line](https://genetixbay.com/knowledge/glossary/inbred-line.md)

## Read more

- [F1, F2, F3 explained: what filial generations really mean](https://genetixbay.com/knowledge/breeding/f1-f2-f3-explained.md)
- [Inbreeding depression and hybrid vigour](https://genetixbay.com/knowledge/breeding/inbreeding-depression-hybrid-vigour.md)

## Sources

1. Allard RW. 1999. Principles of Plant Breeding, 2nd edition. John Wiley & Sons, New York. ISBN 978-0-471-02309-0
2. Schnable PS, Springer NM. 2013. Progress toward understanding heterosis in crop plants. Annual Review of Plant Biology 64:71-88. https://doi.org/10.1146/annurev-arplant-050312-120145