# F2

> F2 is the second filial generation, made by crossing or selfing F1 plants; it shows the widest segregation, bringing back hidden recessives and new combinations.

- Canonical: https://genetixbay.com/knowledge/glossary/f2.html
- Also written: second filial generation, F2 generation, F2s, F2 seed
- 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"

F2 is the generation produced by crossing [F1](https://genetixbay.com/knowledge/glossary/f1.md) plants with each other (or selfing an F1). Each F1 parent passes one of its two [alleles](https://genetixbay.com/knowledge/glossary/allele.md) at random, so the F2 contains every combination of the original parents' alleles in [Mendelian ratios](https://genetixbay.com/knowledge/glossary/mendelian-inheritance.md): 1:2:1 genotypes at each locus, 3:1 visible ratio for a dominant trait.

## In practice

The F2 is the breeder's hunting ground. [Recessive traits](https://genetixbay.com/knowledge/glossary/recessive.md) hidden in the F1 reappear, and new combinations show up that neither grandparent had. That is why [autoflowering](https://genetixbay.com/knowledge/glossary/autoflower.md), specific colours or rare aromas from one grandparent are often recovered in an F2 rather than an F1.

The trade-off is variation. An F2 pack can range from tall to short, fast to slow, and fuel to fruit. Expect to grow more plants: for a wanted combination of two recessive traits, about 1 in 16; for three, about 1 in 64.

## Don't confuse with

- **F1**: the uniform (or less variable) first cross.
- **F3 and later**: produced by crossing selected F2s; [segregation](https://genetixbay.com/knowledge/glossary/segregation.md) narrows as selection continues.
- **S1**: selfed seed from one plant; similar segregation to an F2 of that plant's genotype, but every seed is female and [inbreeding](https://genetixbay.com/knowledge/glossary/inbred-line.md) is higher.

## Related terms

[F1](https://genetixbay.com/knowledge/glossary/f1.md), [Filial generation](https://genetixbay.com/knowledge/glossary/filial-generation.md), [Segregation](https://genetixbay.com/knowledge/glossary/segregation.md), [Pheno hunt](https://genetixbay.com/knowledge/glossary/pheno-hunt.md), [Recessive](https://genetixbay.com/knowledge/glossary/recessive.md)

## Read more

- [F1, F2, F3 explained: what filial generations really mean](https://genetixbay.com/knowledge/breeding/f1-f2-f3-explained.md)
- [Selection and pheno hunting: sample sizes and scoring rubrics](https://genetixbay.com/knowledge/breeding/selection-pheno-hunting.md)

## Sources

1. Allard RW. 1999. Principles of Plant Breeding, 2nd edition. John Wiley & Sons, New York. ISBN 978-0-471-02309-0
2. Miko I. 2008. Gregor Mendel and the principles of inheritance. Nature Education 1(1):134. https://www.nature.com/scitable/topicpage/gregor-mendel-and-the-principles-of-inheritance-593/