The Same Grow, Two Different Packs

Put two packs of CBD seeds beside each other, one marked 1:1 and the other 20:1, and the two look the same: the same breeder’s packaging, the same seed count, seeds which no eye can tell apart. Run them in the same tent and they part ways at the very first stage and do not meet again. The cause is a single gene, and the clearest way to understand what it does is to track the two packs along every stage both share: the cross that produced them, the seed, the seedling, the flowering tent, the cut, the jar, the lab bench and the border. The lines used as examples below are drawn from the range at https://calmcbdseeds.com, which runs 1:1, 2:1 and 20:1 and a top line at about 30 to one; the biology holds the same regardless of which shop the seeds come from.

Before the Seed Exists

Cannabis decides whether it will make THC or CBD at one position on the genome. The gene there exists in two versions: one codes the enzyme that converts the shared precursor into THCA, the other the enzyme that turns it into CBDA. Each plant carries two copies, one inherited from either parent, and the pair sets the chemotype. Two THC copies give a THC-dominant plant. Two CBD copies give a CBD-dominant one. One of each makes a balanced plant, since the two forms are codominant and not one of them overrides the other.

The 1:1 pack was made by crossing two balanced plants, each carrying one copy of each form. The CBD-dominant pack was made by crossing two plants that each hold two CBD copies and no THC copy in either of them. That one difference at the cross determines everything afterwards, and the difference is fully inside the seed long before it is packed.

The Mendelian Split

Cross two balanced plants and the offspring sort themselves by the simplest arithmetic in genetics: a quarter get two THC copies, a quarter get two CBD copies, half inherit one of each. In a pack of 10 seeds that works out to, on average, around two THC-dominant seeds, two or three CBD-dominant ones, and about five true balanced ones. The pack is labelled by its parents, and for half its contents the label fits; for the other half it does not. Calm CBD Seeds states the expected split on each balanced pack, which means the buyer sees ahead of sowing that a share of the plants are going to differ from the stated ratio.

The CBD-dominant pack has no such split. Each seed received a CBD copy from each parents, every plant is going to be CBD-dominant, and the ratio on the foil holds to every one of them, give or take the ordinary differences in how total cannabinoid any individual plant produces. Breeders describe such lines “breed true” for chemotype; the phrase refers to exactly this lack of variation.

Where Nothing Shows

Here the two packs look the same again, and the resemblance lasts further than most growers expect. Chemotype leaves no mark on a seedling. Leaf, vigour, stem spacing and growth rate are governed by other genes entirely, and the three chemotypes of plant in the 1:1 pack come up indistinguishably from one another and from each plant in the CBD-dominant pack.

The one real difference at this stage arises from lineage not chemotype. Lines with strong hemp genetics, and that covers a number of older CBD-dominant lines, tend to stretch rangier and fill out less. A well-worked 20:1 line behaves like any indoor hybrid; a young one may still carry the hemp in its shape. Not one of these tendency tells a thing about the ratio to come.

When the Resin Comes In

In flower the two packs begin to offer clues, and most of the clues point the wrong way. Trichome density is the usual thing a grower judges, and it was a reasonable rule: first-generation CBD-dominant lines showed visibly less resin than their THC counterparts, an unwanted legacy from hemp. Current lines have mostly closed that gap, and a lightly resinous plant from the CBD-dominant pack may still test exactly where the foil promised. Trichome density and chemotype are inherited on separate genes.

Smell is an even poorer guide. The terpene profile lives on yet other genes, so the THC-dominant plant hiding in the 1:1 pack can smell indistinguishable to the balanced one next to it, and either can smell indistinguishable to a plant from the CBD-dominant pack. People who try to sort a balanced pack by nose in week eight are guessing, which is no any better than not unsorted at all.

One Place CBD Is More Forgiving

At this stage the two packs differ in a way that benefits the grower of the CBD-dominant pack and also the CBD-dominant plants sitting in the 1:1 pack. CBDA degrades more gradually than THCA, so a CBD-dominant plant allowed a week past its peak retains most of its cannabinoid content, where a THC-dominant one under the same conditions has already begun shedding THC to CBN. The usual trichome rules nonetheless holds; it applies on account of the terpenes, which fade on every plant whatever the chemotype, and a late, rushed CBD flower smells of little whatever the test result is.

Why Each Plant Gets Its Own Label

The CBD-dominant pack goes into one jar. Every plant from it holds about the same ratio, and blending them alters nothing worth notice. The 1:1 pack cannot be treated the same way. Pool its 10 plants into a single jar and the result become a ratio that no foil could have predicted, skewed by whichever plants grew biggest, and no subsequent test can untangle the plants that went in.

The discipline that prevents the grief is almost tedious: harvest the balanced pack plant by plant, cure each apart, number each, and try each one one at a time rather than after anything is combined. It is the only stage in the whole grow where the three kinds of plant in the 1:1 pack can yet be kept apart without a lab, and only because each is still in its own bag.

Stage Seven: The Lab Report

Send a sample from each jar to a laboratory and the two packs finally become readable. For the CBD-dominant pack the reports come back clustered tightly near the advertised ratio, varying mainly in total cannabinoid content not in balance. For the 1:1 pack they come back in three groups: a few plants showing almost all THC, some with nearly all CBD, and the rest somewhere near one to one. Nothing of this result is a defect; it is the breeder’s cross expressed as numbers.

Home test kits are sold for growers without a laboratory, and most detect whether THC is present rather than how much. That is enough to pull the THC-dominant jars away from a balanced pack and not to put a ratio to the rest, which suits the most frequent use: finding out what of the 10 jars is going to catch out a guest.

Stage Eight: The Border

The last stage at which the two packs diverge is in law, and it trips growers who thought “CBD” meant “hemp”. Most jurisdictions classify hemp by a THC ceiling, a small fraction of a percent of dry weight, with the exact figure differing from country and year to year. A plant from the CBD-dominant pack making twenty percent CBD at twenty to one also makes around one percent THC, which is several times above most limits. Certified hemp cultivars are bred to hold total cannabinoid output low so the THC fraction remains below the line right up to maturity; CBD seed lines are bred for high output and allow the THC rise with it. A seller that offers only a ratio is describing a flower line; a grower who requires a legal hemp crop should look for a tested THC figure at maturity and order no line that cannot provide one.

Past the threshold question, the word on the foil changes nothing in the law on the seed as such. Where holding cannabis seeds is permitted and germinating them is not, the 1:1 pack and the CBD-dominant pack fall in the same position as every other pack. Where the plant is legal without restriction, the choice between them is the grower’s and nothing else’s. No part of this page is legal advice, and the rule which counts is the one where the seed is going to be grown, not the one where it was bought.