Why one packet of seeds gives different plants
Ten seeds from one packet do not give ten identical plants. They give ten siblings, and siblings differ — in height, in structure, in maturation time, in aroma, and in the proportions of the compounds they produce.
This surprises people who expect a named variety to be a specification. It is not one. A variety name describes a population within which individuals vary, and the amount of variation depends on how much breeding work went into narrowing it.
This page covers where the variation comes from, what varies and what does not, how growers select within it, what stabilisation actually involves, and why none of it is visible on a package.
⚠️ Scope. This page describes a process and what can be verified from documents. It does not describe what a product does to a person, gives no amounts, and does not replace a healthcare professional.
🔴 Genotype and phenotype
The genotype
The genetic complement a plant carries. It is fixed at fertilisation and does not change for the rest of the plant’s life.
The phenotype
What the plant actually becomes: its height, structure, timing, aroma and composition. It is the genotype expressed under a particular set of conditions.
Why the distinction matters
Two plants with identical genotypes grown differently produce different phenotypes. Two plants with different genotypes grown identically also produce different phenotypes.
What follows
Observing a plant tells you about the combination, not about either component alone.
Where sibling variation comes from
Recombination
Each parent contributes one of each chromosome pair, and which one is a matter of chance. The number of possible combinations is very large.
Crossing over
Chromosomes exchange segments during the formation of reproductive cells. This shuffles the combinations further, within chromosomes rather than just between them.
What that produces
Siblings sharing roughly half their genetics with each other, in different halves. They are related and they are not the same.
Why it cannot be avoided
It is how sexual reproduction works. Any seed-produced population varies, and the only way to remove the variation is to stop using seed.
How much variation to expect
From a wide cross
Two dissimilar parents give siblings that differ substantially. It is the starting point of breeding and it is not what a production grower wants.
From a stabilised line
Many generations of selection narrow the population. Siblings still differ and the differences are smaller and less consequential.
What determines it
Purely the breeding history. A variety worked on for a decade behaves very differently from a cross made last season.
What a packet says about it
Nothing, generally. The breeding history behind a variety is rarely stated and never verifiable.
What varies visibly
Height and structure
Some siblings stretch and others stay compact. In a room with fixed light height this alone can determine which plants do well.
Internodal spacing
The distance between branch points, which determines how dense the eventual structure is.
Leaf morphology
Width, count and colour vary between siblings, and it is the first difference a grower notices.
Maturation timing
Siblings can finish days or weeks apart. On a single-harvest crop this matters more than any other variable.
What varies invisibly
The cannabinoid ratio
Siblings differ measurably in the proportions of the compounds they produce. It is the variation that matters most commercially and the one nobody can see.
The terpene profile
Aroma differs between siblings, sometimes markedly. It is perceptible without instruments and it is not quantified without them.
Yield
Two siblings of similar appearance can differ substantially in what they actually produce. It is only known at harvest.
Resilience
Tolerance of heat, drought, and pathogen pressure varies between siblings and only becomes apparent under stress.
The selection a grower runs
What it is
Growing a population, observing every individual, and keeping the ones that perform best. It is ordinary selection and it has no shortcut.
What is observed
Structure, timing, yield, aroma, and where the grower can afford it, a laboratory analysis of the composition.
How many plants
Enough that the best of them is genuinely good. A handful gives a poor chance; dozens give a better one.
What happens to the rest
They are grown out and harvested like any other plant. The material is fine; it simply was not the one being looked for.
What happens to the plant that is kept
It becomes a mother
The selected individual is held in vegetative growth and reproduced by cuttings. Everything afterwards is a copy of that one plant.
Why that resolves the variation
Because cuttings do not recombine. Once the selection is made, the variation problem is solved for as long as the line lasts.
What it does not resolve
The next selection. When the line declines, the process starts again with a new population.
Why growers keep records
Because a good selection is worth reproducing and a poor one is worth not repeating. The population grown and the individual kept are both worth writing down.
Stabilisation
What it means
Reducing the variation in a seed population so that siblings resemble each other more closely generation after generation.
How it is done
Selecting individuals that express the wanted traits, crossing them, and repeating. Each generation narrows the population.
How long it takes
Many generations, over years. It is the slow part of breeding and it is what separates a worked variety from a recent cross.
What is lost
Genetic diversity. A stabilised line is more predictable and less resilient, which is the standard trade in any crop.
The generational vocabulary
The first cross
The offspring of two distinct parents. They are uniform in some respects and carry no fixed combination of traits.
The second generation
Crossing those offspring together produces much greater variation, as the parental combinations segregate. It is the generation breeders select in.
Later generations
Successive selection and crossing narrow the population toward the wanted type. Progress slows as uniformity increases.
Backcrossing
Crossing offspring back to one parent, to recover a trait that parent had. It is a targeted tool rather than a general method.
🔴 What this does to variety names
The expectation
A buyer seeing a variety name generally expects a specification, as with a product model number.
The reality
The name describes a population, whose members vary by an amount that depends on breeding history the name does not convey.
Why two products with one name differ
Because they are different individuals from that population, grown by different people under different conditions.
What that means for comparison
A variety name narrows a search and does not settle a comparison. The certificate does the settling.
The catalogue and uniformity
What is required
A variety cultivated for the compliant market must appear in the common catalogue of varieties of agricultural plant species and stay within the total THC limit.
The three criteria
Distinctness, uniformity and stability. The examination tests all three against defined protocols.
What uniformity means there
Variation within accepted tolerances for the characteristics examined. It does not mean identical individuals.
Why it matters here
A catalogue variety has had its variation formally assessed. A commercial name that is not a catalogue name has not.
What growing conditions add
The environmental half
The same genotype produces different phenotypes under different light, temperature, nutrition and water. Some of what looks like genetic variation is not.
How growers separate them
By growing siblings side by side under identical conditions. Differences that remain are genetic; differences that do not are environmental.
Why this is rarely done properly
Because it requires space and discipline, and most selection happens informally in a production room rather than in a trial.
The consequence
Some selections are made on environmental noise rather than genetics, and the chosen plant disappoints when reproduced.
What a buyer sees of any of this
Batch variation
Successive purchases of the same reference differing noticeably can indicate a seed crop rather than a clone line.
Within-package variation
Flowers differing in size, density or aroma within one purchase, which a seed crop produces naturally.
What it is not
A defect. A seed crop varies by construction and the material is not worse for it.
What is never recorded
Which individual, from which population, produced the crop. Nothing carries it.
The honest position on variety names
What they convey
A general character and a family resemblance. That is real and it is useful for narrowing a choice.
What they do not convey
Composition, potency, or anything measurable. Two products under one name can differ substantially on every measured axis.
What settles it
The certificate, which measures the batch that is actually being sold rather than the population it came from.
The reasonable use
Names to shortlist, certificates to choose. It is the same division that applies everywhere in this subject.
What a proper selection trial looks like
The setup
Siblings grown side by side in one space, under identical light, feed and watering, with position rotated so that no plant benefits from a better spot than another.
Why the controls matter
Without them, a plant nearest the light outperforms one at the edge, and the grower selects for position rather than for genetics. It is the commonest failure in informal selection.
What is recorded
Height and structure at fixed intervals, the date each plant enters and completes flowering, the harvested weight, and where the budget allows, a composition analysis of each.
Why writing it down matters
Because selection is a comparison across weeks, and memory does not hold a dozen plants accurately over that span. The record is what makes the comparison real.
The analysis that changes a selection
What it adds
Composition figures for each candidate, which no amount of observation provides. Two plants that look and smell equally good can differ substantially in what they contain.
What it costs
An analysis per plant, which on a population of any size becomes the dominant cost of the selection.
How growers manage it
By narrowing on observable traits first — structure, timing, yield, aroma — and analysing only the finalists. It is the obvious compromise and it is what most operations do.
What it changes
Selections made with data behind them survive better than selections made on impression. It is the single largest improvement available to a small breeding effort.
Why a good selection can still disappoint
The environment moves
A plant selected in one room, in one season, under one feeding regime, may not repeat in another. Part of what was selected was the interaction rather than the genetics.
The line ages
The chosen individual becomes a mother, and mothers accumulate pathogens and drift over years. What declines is the line rather than the original judgement.
The market moves
A selection made for one set of preferences can be overtaken by a change in what buyers want. The plant did not get worse.
What follows
A selection is a decision valid for a period, not a permanent achievement. Growers who take it as permanent are the ones surprised when it stops working.
What the variation is worth
The case against it
It complicates every operation, it makes harvest timing a compromise, and it makes a crop unpredictable. Production growers eliminate it for good reasons.
The case for it
It is the only source of anything new. Every variety that exists came out of a population that varied, and every future one will too.
Where both hold
At different points in the chain. Variation belongs in the selection stage and not in the production stage, which is exactly how the industry organises itself.
What that means for a buyer
Consistency is a production achievement and variation is a breeding necessity. Encountering the second in a finished product usually means the two stages were not separated cleanly.
A short glossary
Genotype
The genetic complement a plant carries, fixed at fertilisation and unchanged thereafter.
Phenotype
What the plant actually becomes, being the genotype expressed under a particular set of conditions.
Recombination
The shuffling of parental genetics during the formation of reproductive cells, which is why siblings differ.
Stabilisation
Reducing variation in a seed population through successive generations of selection and crossing.
Common catalogue
The European register of agricultural plant varieties permitted for cultivation and marketing in the Union, where uniformity is formally assessed.
The five checks that apply to any product
The batch certificate
Request it with the number printed on the packaging. A general document for the product line does not cover this batch, and those differences are exactly what it should record.
Total THC
Delta-9-THC plus THCA multiplied by 0.877, because THCA becomes THC under heat and the limit applies to the sum, not to either value alone.
Price per milligram
A division, not an opinion. The only figure that makes two products comparable, whatever the format, process and pack size.
The claims
Without an authorisation number in the EU Register these are assertions, not data — and for cannabidiol that register contains no authorised entry to this day.
The seller’s details
Company name, address and contact. Without them there is also no counterparty to turn to if something turns out to be wrong.
How this connects to the rest
With clones and seed
Clones eliminate this variation entirely. That is the whole reason commercial production runs on them.
With variety naming
The variation described here is why a name is a family resemblance rather than a specification.
With the catalogue
A catalogue variety has had its uniformity formally examined. A commercial name has not.
With the certificate
It measures the batch actually being sold, which is the only thing that settles a comparison.
What this is for in practice
When two products with one name differ
That is expected. They are different individuals from a varying population, grown by different people.
When a package varies internally
It suggests a seed crop. It is a production model rather than a fault.
When a variety name is quoted
Ask whether it is the catalogue name. That is the one with an examination behind it.
When choosing
Names to shortlist, certificates to decide. The name cannot do the second job.
Frequently asked questions
Why do siblings from one packet differ? Because sexual reproduction recombines parental genetics. Each seed receives a different combination, and the differences are real.
How much should they differ? It depends entirely on breeding history. A recent wide cross varies substantially; a line worked on for years varies much less.
What varies visibly? Height, structure, internodal spacing, leaf form and maturation timing. The last of these matters most on a single-harvest crop.
What varies invisibly? The cannabinoid ratio, the terpene profile, yield and stress tolerance. None can be seen and all can be measured.
What is a pheno-hunt? Growing a population, observing every individual, and keeping the best one as a mother to reproduce by cuttings.
Does the environment contribute? Substantially. The same genotype under different conditions gives different phenotypes, which is why proper selection compares siblings side by side.
What does stabilisation involve? Successive generations of selecting and crossing the wanted type, narrowing the population. It takes years and it costs genetic diversity.
Does a variety name guarantee anything? It conveys a general character. It does not specify composition, potency or anything measurable.
What does the catalogue examine? Distinctness, uniformity and stability, against defined protocols. Uniformity there means variation within tolerances, not identical plants.
How do I compare two products? By their certificates. The name narrows a search and cannot settle a comparison.
What we check and what we do not
We check what can be checked from documents: official registers, declared contents, certificates of analysis, arithmetic. We test no products, rank nothing, and assert no effects.
The gap between what a variety name promises and what it delivers is one of the most persistent sources of confusion in this subject, and it comes down to something quite simple: a name describes a population, and populations vary.
How much they vary is the part nobody states. A line worked on for a decade and a cross made last season can carry equally confident names, and only one of them describes something narrow enough to be predictable. The certificate measures what actually arrived, which is why it remains the thing that settles a comparison.