Cannabis growing and breeding glossary

F1 in cannabis means the first filial generation: the offspring of crossing two parents, written female first (female x male). F1s of unrelated parents typically show the strongest hybrid vigour, outperforming the parents' average. Crossing F1 siblings gives the F2, where allele pairs segregate and create much more variation. In cannabis, 'F2' usually means sibling-crossed F1s, not selfed plants.

A genotype is a cannabis plant's genetic make-up; a phenotype is what you actually observe, which is the genotype plus the environment plus their interaction. Two clones share a genotype but can look different in different rooms. Growers also use 'pheno' loosely to mean one individual plant from a seed lot, as in 'the #4 pheno', which is really one distinct genotype among siblings.

An IBL (inbred line) is a cannabis population inbred over several generations until it breeds fairly true, so seedlings come out much more alike than in a hybrid. No fixed number of generations defines an IBL, so treat the label as a breeder's claim and check the line's documentation. Close inbreeding can also cause inbreeding depression, as hidden harmful recessives become homozygous.

S1 means seed from a cannabis plant pollinated by itself (selfed), usually by reversing one branch or a clone of the same plant so it makes pollen. Because that pollen comes from a female, S1 seed is nearly all female. GenetixBay treats repeated selfing, such as S1 on S1, as a main source of herm-prone lines, so an S1 label deserves a close look at the breeder's grow-out data.

A clone-only, or 'cut', is a selected individual cannabis plant kept only as clones, so the name refers to one specific genotype rather than a seed line. Every rooted cutting is genetically identical to its source, barring rare mutations, and the cut is maintained by keeping mother plants vegetative. Because no seed version exists, the genotype survives only as long as someone keeps it alive.

A chemotype or chemovar is a cannabis plant classified by its chemistry rather than its name or looks. The standard scheme has five types: chemotype I is THC dominant, II mixes THC and CBD, III is CBD dominant, IV is CBG dominant and V is near cannabinoid-free. The THC and CBD synthase alleles behave close to codominant, so a plant carrying one of each tends toward the mixed type II.

BX means backcross: offspring crossed back to one of its own parents. The generations are numbered BX1, BX2 and so on, also written BC1 and BC2. Breeders use backcrosses to steer a line back toward one parent's traits. The convention for writing any cannabis cross lists the female first (female x male), so the pedigree shows which way each backcross was made.