A grower’s guide to what is on the pack
Seed Genetics & Stability
F1, F2, BX3, “stabilised”, “IBL” — the vocabulary on a seed pack describes how much variation is left in the line, which is really a question about how predictable your harvest date is. This page explains what those terms mean, how the work behind them is done, and why a loose line costs more here than it does in most places.
Where we sit in this
We are a retailer. We did not originate the cultivars in this catalogue and we do not run a breeding programme — Gorilla Glue, Northern Lights, White Widow and the rest came from breeders who are named on the strain page wherever we know who they were, and left blank where we do not.
That is worth saying plainly on a page about genetics, because plenty of seed shops imply otherwise. What we do is choose which lines to stock and pass on what the breeder published about them. The figures on every strain page come from the breeder or a cited reference; where a figure does not exist, the field stays empty instead of being filled with something plausible.
The germination guarantee is a separate thing again, and it is a commercial promise rather than a laboratory claim: seeds that fall short are replaced, same strain and pack size, at no cost. The terms are on our returns page.
How a line gets fixed
Reading a population, not a plant
Any well-known cultivar is a range rather than a single plant. Grow out fifty seeds of one and they will not all finish in the same week, and they will not all produce the smell the name is famous for. Breeders start by growing that population under one set of conditions and writing down what each plant actually did — how tightly the nodes stacked, when it finished, how much resin it threw, and how the aroma moved over the last three weeks.
Choosing against notes, not favourites
Most of that population is then discarded. What is kept is the group that hit the target on the record sheet: finished on time, smelled right, held itself up without support. The reason breeders select against written figures rather than the plant they liked best is that impressions do not repeat and measurements do.
Filial generations and backcrossing
Cross two selected parents and you get an F1 — vigorous, often impressive, and genetically all over the place. Cross the F1s and you get an F2, where the variation actually shows up. Getting from there to a pack that grows evenly means either many filial generations of selection, or crossing a selected plant back to its own parent line — BX1, BX2, BX3 — until the trait is fixed. This is the slow, unglamorous part, and it is the part that gets skipped.
What the pack label does and does not tell you
"F1" on a pack means hybrid vigour and variation together. "Stabilised", "IBL" or a BX number means somebody spent generations removing that variation. Neither term is regulated, so it is a claim rather than a certificate. The practical test is the one you already have: a stable line grows you the same plant next season, and an unstable one does not.
Why a loose line costs more in a South African season
Somewhere with a long dry autumn, an uneven pack is a nuisance — the slow plants come down late and that is the end of it. Here the calendar argues back. The country spans roughly 22°S to 35°S, the rain falls in summer across most of it and in winter in the Western Cape, and a plant that still wants three weeks in April is usually not going to get them. Stability is the thing that turns a flowering time printed on a strain page into a date you can plan a season around.
A flowering spread of three weeks
The expensive one. If half the pack is ready in week nine and the rest wants week twelve, the tail end lands in May — and May is not one thing in this country. On the frost-free KwaZulu-Natal coast it is still workable. On the Highveld it is over. A tight line lets you choose the harvest date; a loose one hands that decision to the weather.
Plants that are simply the wrong shape
Two seeds in ten come up stretchier, looser and smelling of something else entirely. Where you have four sites under a light, that is half the run given over to plants you did not set out to grow.
Aroma that will not sit still
One plant comes out citrus-forward and the next one flat and green, from the same packet and the same feed. Terpene profile is settled in the genetics long before your cure gets near it, and an unfixed line has not settled on anything.
Yield you cannot budget for
When per-plant output varies twofold inside one packet, you cannot size anything around it — not the room, not the light, not the feed. A figure that is really a range is not a planning number.
Reversal when the weather turns
Feminised lines that were never properly fixed will throw male flowers under stress, and a South African spring provides stress on schedule: a warm fortnight, then a cold snap. It takes one reversal to seed everything around it.
Nothing carries to next season
You find a plant that works, buy the same seeds a year later, and get a different one. Everything you worked out about feeding and timing that cultivar stops being worth anything.
What a well-fixed pack actually buys you
A date instead of an average. When the whole pack comes down together, the flowering time stops being a mean and starts being something you can count backwards from — which is the only way to plan against a frost date.
Work that carries forward. What you learn about feeding, training and timing one cultivar is still worth something next season, because next season’s pack grows the same plant.
An aroma that holds across the pack. Terpene expression is settled in the line before your dry and cure get a say. Every plant in a fixed pack smells the way the name led you to expect.
More on how we handle strain information is on our about page, or you can start from feminised seeds and autoflowering genetics.