Backcross (BX)
Definition: A backcross, labeled BX on seed packs, is a breeding step where offspring are crossed back to one of their parents, usually a prized female clone. Each round increases that parent's share of the genetics and reinforces its traits. Breeders backcross to preserve a famous plant's character in seed form.
How Backcross (BX) works
Many legendary strains exist only as clones. To sell them as seeds, a breeder crosses the clone with a male, then takes the best offspring and crosses them back to the original clone. The numbers on the label track how many times that has happened:
- BX1: offspring carry about 75% of the recurrent parent’s genetics.
- BX2: about 87.5%.
- BX3: about 93.75%. Some breeders call a third backcross a cubed line.
Why backcrossing works
Each backcross halves the remaining genetic contribution from the outside parent. Selecting offspring that look and smell most like the target clone speeds things up, since it filters out stray traits faster than the averages suggest.
What it means for growers
A BX3 seed gives you a strong chance of finding plants close to the original clone, but not a guarantee. Expect most plants to resemble the target, with a few outliers. Backcrossing also concentrates any weaknesses the recurrent parent carries, such as mold susceptibility, so research the parent’s reputation along with the hype. It is one of the main tools in stabilization, alongside sibling crossing toward an IBL.