A test grow, or tester grow, is a grow-out of a new seed line before it is released or featured. Testers, ideally independent and in different environments, grow the seed and report germination rate, vigour, uniformity, flowering time, aroma, yield, lab results and any intersex plants.
In practice
Tester data is what turns a cross into a line someone can trust. It also shows genotype by environment effects: a line that behaves in one breeder's room may stretch or mould in another's.
Sample size matters, especially for herm rates. Ten clean plants cannot distinguish 0% from 20%: a line that herms 1 time in 5 shows no herms in 10 plants about 11% of the time. Demonstrating a herm rate under 2% with reasonable confidence needs about 150 plants. GenetixBay's Bay Lines, Seed Club and featuring require a confirmed herm rate under 2% in tester grows.
Chance of seeing zero herms in n plants when the true rate is p: (1 - p)^n. Rule of three: zero events in n plants gives a 95% upper bound of about 3/n, so 150 clean plants supports a rate under 2%.
Don't confuse with
- Progeny test: testing a parent by its offspring.
- Pheno hunt: selecting individuals from seed, not validating a line.
Myth check
"A 10-plant test grow proves a line is herm-free" is busted; see Mythbusters.
Germination is the stage where a viable seed absorbs water, splits its shell and pushes out a root (radicle), usually within 1-7 days at 20-30 °C.In cannabis growing, a plant (usually female) that develops both pistillate and staminate flowers or anthers; botanists call it intersex or monoecious expression.The genotype is the set of alleles a plant actually carries, either at one locus or across its whole genome, as opposed to the traits you can see.The stretch is the rapid increase in height in the first two to three weeks after switching to flower, when many cultivars grow 1.5 to 3 times taller.The herm threshold is GenetixBay's two-tier herm standard: a 10-plant screening grow with zero herms to be featured, then about 150 or more community-grown plants before a line can be Verified under 2% herm rate.Bay Lines are GenetixBay's community breeding programme: lines bred from member-nominated keepers and documented males, tested and released with full records.The Seed Club is GenetixBay's seed programme run through a licensed partner, offering tested seed lots with published batch records where the law allows.A progeny test judges a parent by growing out and measuring its offspring, the most reliable way to know what a plant, especially a male, actually passes on.A seed run is a dedicated grow in which selected parents are crossed to produce a batch of seed, as opposed to growing for flower.Uniformity is how alike the plants of one seed batch are for traits such as height, timing and chemistry; F1s of inbred parents and IBLs are most uniform.Genotype by environment interaction (GxE) is when different genotypes respond differently to the same change in conditions, so the best cultivar in one room may not be best in another.A pheno hunt is growing many seeds of one line side by side and evaluating them to select the best individual plants, which are then kept as clones.
