# Mythbusters: grow lore, put on trial > 33 popular cannabis growing myths checked against the evidence, from flushing and darkness before harvest to Cal-Mag under LEDs, with verdicts and the open GenetixBay trials. - Canonical: https://genetixbay.com/knowledge/mythbusters.html - Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay Knowledge Base (genetixbay.com/knowledge)" ## Greenleaf's standing challenge: darkness before harvest Putting plants in 24–72 hours of darkness before harvest is a myth ("complete and utter nonsense", in the founder's words). For more than 20 years the founder has offered a 50-pack of seeds to anyone who finds a peer-reviewed study showing a benefit (not a single-plant study, not biased or skewed). Nobody has claimed it. ## Busted - **Myth:** "Cannabis is much stronger than it was 20 (or 50) years ago" **Verdict:** Busted. False as a claim about the genetics. Hashish, charas and sinsemilla traditions are centuries old and impossible with 5 % plants. The 'weak old weed' numbers measured seized, degraded, exported brick, not the best of what was grown Evidence: [Old cannabis wasn't weak: the "so much stronger than 20 years ago" myth](https://genetixbay.com/knowledge/genetics-history/old-cannabis-was-not-weak.md) - **Myth:** "Most shelf weed is 30 %" **Verdict:** Busted. Independent retests find most retail flower in the mid-teens to low 20s, often well below its label. Reaching 30 % total cannabinoids is a rare, real feat Evidence: [Buyer beware: potency labels, strain names and other claims that don't hold up](https://genetixbay.com/knowledge/basics/buyer-beware-label-claims.md) - **Myth:** "Flower can test 35 %, even 42 %, total cannabinoids" **Verdict:** Busted. Not credible: cannabinoids are made only in trichome heads and bud is mostly bract and stem. Numbers like that come from concentrates, lab shopping or inflated testing Evidence: [Buyer beware: potency labels, strain names and other claims that don't hold up](https://genetixbay.com/knowledge/basics/buyer-beware-label-claims.md) - **Myth:** "Humidity packs keep your stash fresher" **Verdict:** Busted. A marketing gimmick: the only pro-pack data is the manufacturer's own. A good cure in a full, airtight, dark jar does the job Evidence: [Buyer beware: potency labels, strain names and other claims that don't hold up](https://genetixbay.com/knowledge/basics/buyer-beware-label-claims.md) - **Myth:** "Frost and purple mean potency" **Verdict:** Busted. Frost is how many trichome heads you can see, not how full they are; gland density didn't predict THC in a field study, and consumers' potency ratings didn't match measured THC. Purple and red are anthocyanins, set by genetics and cold, with their own temperature optimum separate from cannabinoids Evidence: [Buyer beware: potency labels, strain names and other claims that don't hold up](https://genetixbay.com/knowledge/basics/buyer-beware-label-claims.md) - **Myth:** "Autos are easy" **Verdict:** Busted. Autos run on a strict countdown from germination, so any stress or mistake costs yield they can't recover. They're good for beginners because they quickly show who has a green thumb, not because they're forgiving Evidence: [Photoperiod vs autoflower, and how autoflowering is inherited](https://genetixbay.com/knowledge/basics/photoperiod-vs-autoflower.md) - **Myth:** "UV-B lamps raise THC" **Verdict:** Busted. Controlled trials found UV made little or no difference to cannabinoids, and high doses can cut yield Evidence: [Light spectrum: blue, red, far-red and UV, what's real](https://genetixbay.com/knowledge/environment/light-spectrum.md) - **Myth:** "Cold nights boost terpenes and resin" **Verdict:** Busted. Cold can bring out purple colour (anthocyanins) in cultivars that carry it. More terpenes, flavour or resin from cold has no peer-reviewed support Evidence: [Temperature by stage: day, night and root-zone targets](https://genetixbay.com/knowledge/environment/temperature-by-stage.md) - **Myth:** "Day 1 of 12/12 is day 1 of flower" **Verdict:** Busted. After the flip the shoot tip needs days to rebuild itself into an inflorescence; in controlled studies the first proper pistil clusters appeared about 8–14 days after short days began, and later in slow cultivars Evidence: [The flip isn't day 1 of flower: the 10–14 day transition and how to count it](https://genetixbay.com/knowledge/environment/flip-to-flower-transition.md) - **Myth:** "High-phosphorus bloom boosters mean bigger buds" **Verdict:** Busted. Four independent cannabis trials found a plateau: past roughly 25–60 mg/L P, more phosphorus didn't raise yield or cannabinoids Evidence: ["Bloom boosters" for cannabis: what's real and what's marketing](https://genetixbay.com/knowledge/nutrients/bloom-boosters.md) - **Myth:** "LED lights make plants need Cal-Mag" **Verdict:** Busted. LEDs don't create a Cal-Mag need. Demand is driven by cultivar, RO or soft water, coco's cation exchange and root-zone pH Evidence: [Cal-Mag: what it is, when you need it and when you don't](https://genetixbay.com/knowledge/nutrients/cal-mag.md) - **Myth:** "A pre-harvest flush 'cleans' the plant of nutrients" **Verdict:** Busted. Plain water can't pull stored minerals back out of tissue. The only valid flush treats the medium (salt build-up), not the plant Evidence: [Flushing before harvest: myth (summary)](https://genetixbay.com/knowledge/nutrients/flushing.md) - **Myth:** "Molasses in the reservoir sweetens and fattens buds" **Verdict:** Busted. Sugars feed soil microbes, not the plant, which makes its own by photosynthesis. In mineral hydro they just feed slime Evidence: [Per-element feeding tricks: what growers adjust, stage by stage](https://genetixbay.com/knowledge/nutrients/per-element-tricks.md) - **Myth:** "More sulfur means more terpenes" **Verdict:** Busted. Terpenes contain no sulfur. Once S is sufficient there's no mechanism for extra S to make more of them Evidence: [Per-element feeding tricks: what growers adjust, stage by stage](https://genetixbay.com/knowledge/nutrients/per-element-tricks.md) - **Myth:** "Late-flower bananas are normal" **Verdict:** Busted. Late 'nanners' are staminate flowers (anthers) forming inside a female's buds: that is intersex expression, a herm. Sex expression is heritable, and stress only reveals the plants that carry the weakness Evidence: [Hermaphrodite cannabis (bananas and nanners): what to do](https://genetixbay.com/knowledge/diagnosis/hermaphrodites.md) - **Myth:** "A herm is fine if it's the best plant you've grown" **Verdict:** Busted. Its pollen makes all-female seed that carries the same tendency. Keep it and you spread the problem; cull it and don't breed from it Evidence: [Hermaphrodite cannabis (bananas and nanners): what to do](https://genetixbay.com/knowledge/diagnosis/hermaphrodites.md) - **Myth:** "Two-way humidity packs make a better cure" **Verdict:** Busted. A marketing gimmick: the only data that says packs help comes from a pack maker's own test. Cure by the bud's water activity, and add a fresh bud if a jar goes too dry Evidence: [Curing and burping: jars, humidity and how long](https://genetixbay.com/knowledge/harvest-cure/curing-burping.md) - **Myth:** "Irradiated weed is radioactive" **Verdict:** Busted. Gamma from cobalt-60, e-beam up to 10 MeV and X-ray up to 5 MeV (7.5 MeV with gold or tantalum targets) don't make the product radioactive, the same as irradiated spices. The real questions are terpenes, mycotoxins and disclosure Evidence: [Irradiated cannabis: gamma, e-beam, X-ray, ozone, RF and what they do to your weed](https://genetixbay.com/knowledge/harvest-cure/irradiated-cannabis.md) - **Myth:** "Irradiation has no effect on terpenes" **Verdict:** Inconclusive. Some studies found no significant change. Others measured 10–20 % losses in volatile monoterpenes (up to 38 % for one compound) right after treatment. The effect is small and real. Nobody has shown it's harmless to aroma, and nobody has shown it ruins it Evidence: [Irradiated cannabis: gamma, e-beam, X-ray, ozone, RF and what they do to your weed](https://genetixbay.com/knowledge/harvest-cure/irradiated-cannabis.md) - **Myth:** "A passing retest means the mould problem is gone" **Verdict:** Busted. Irradiation and other kill steps reduce the count of living spores. Toxins the mould already made, and the dead spores themselves, can stay. One small study still found mycotoxins and viable Aspergillus and Penicillium after gamma treatment Evidence: [Irradiated cannabis: gamma, e-beam, X-ray, ozone, RF and what they do to your weed](https://genetixbay.com/knowledge/harvest-cure/irradiated-cannabis.md) - **Myth:** "Flushing with plain water before harvest makes smoother, better-tasting buds" **Verdict:** Busted. Cannabis stores what it takes up; water at the end doesn't wash it out. Controlled studies found no quality gain, and starving the plant while it finishes costs yield and resin Evidence: [Pre-harvest flushing: a myth that costs you yield and resin](https://genetixbay.com/knowledge/harvest-cure/flush-debate.md) - **Myth:** "24–72 hours of darkness before harvest boosts resin and THC" **Verdict:** Busted. Why switch off photosynthesis while the plant is finishing? No credible study shows a benefit, and the founder's 20-year challenge is still unclaimed Evidence: [Trichome ripeness: clear, cloudy, amber, and what the evidence says](https://genetixbay.com/knowledge/harvest-cure/trichome-ripeness.md) - **Myth:** "Amber trichomes mean CBN and couch-lock" **Verdict:** Busted. CBN forms mainly by oxidation after harvest, not on the plant. Amber marks ageing glands, not a different high Evidence: [Trichome ripeness: clear, cloudy, amber, and what the evidence says](https://genetixbay.com/knowledge/harvest-cure/trichome-ripeness.md) - **Myth:** "Crossing two famous cuts makes a new strain" **Verdict:** Busted. Two heterozygous clones give a segregating, untested F1 population, not a uniform or stable strain. A strain is what's left after years of selection and testing Evidence: [Breeders vs pollen chuckers: what real cannabis breeding looks like](https://genetixbay.com/knowledge/breeding/breeders-vs-pollen-chuckers.md) - **Myth:** "Only the females matter in breeding" **Verdict:** Busted. Half of every seed's genes come from the father. Selecting only the mother halves the response to selection, and an unselected male is a gamble on half the genome Evidence: [Breeders vs pollen chuckers: what real cannabis breeding looks like](https://genetixbay.com/knowledge/breeding/breeders-vs-pollen-chuckers.md) - **Myth:** "A 10-plant test grow proves a line is herm-free" **Verdict:** Busted. Ten clean plants can't tell 0 % from 20 %: a line with a 1-in-5 herm rate shows zero herms in 10 plants about 11 % of the time. Claims of under 2 % need about 150 plants Evidence: [Breeders vs pollen chuckers: what real cannabis breeding looks like](https://genetixbay.com/knowledge/breeding/breeders-vs-pollen-chuckers.md) - **Myth:** "If it has the right name, it's the real cut" **Verdict:** Busted. Same-named cuts from different sources are often genetically different; only a documented chain of custody plus a DNA comparison settles it Evidence: [Elite clone-only gatekeeping: why the classics live in a few hands](https://genetixbay.com/knowledge/breeding/elite-clone-gatekeeping.md) - **Myth:** "Legal cannabis is clean because it's tested" **Verdict:** Busted. Regulators have recalled legal flower for aspergillus, failed microbial limits and banned pesticides, and private retests have found residues on licensed shelves. Testing reduces risk; it doesn't guarantee it Evidence: [Craft vs industrial cannabis: did legalisation's commercial model hurt quality?](https://genetixbay.com/knowledge/genetics-history/craft-vs-industrial-cannabis.md) - **Myth:** "Indica = couch, sativa = energy, and they're different species" **Verdict:** Busted. One species, Cannabis sativa, showing different phenotypes. Nearly everything sold is a hybrid, and the labels don't predict chemistry or effects. At most they describe plant shape Evidence: [Indica, sativa and ruderalis: what the names really mean](https://genetixbay.com/knowledge/genetics-history/indica-sativa-ruderalis.md) - **Myth:** "Different names mean different plants" **Verdict:** Busted. Genotyping has found differently named retail samples with identical genotypes, and one state's 637 recorded names collapsed to three chemical profiles. A name is a label, not a genotype Evidence: [Same cut, a thousand names: renaming, relabelling and the shrinking gene pool](https://genetixbay.com/knowledge/genetics-history/same-cut-a-thousand-names.md) - **Myth:** "A new name means new genetics" **Verdict:** Busted. Renaming a cut or a reselection costs nothing and changes nothing in the plant. Only a documented cross, a grow-out or a DNA comparison shows something is new Evidence: [Same cut, a thousand names: renaming, relabelling and the shrinking gene pool](https://genetixbay.com/knowledge/genetics-history/same-cut-a-thousand-names.md) - **Myth:** "If it has the famous name, it's the famous cut" **Verdict:** Busted. Studies of same-named retail samples find genetic outliers in most names. Without a chain of custody or a DNA match to a reference sample, 'the original cut' is a claim Evidence: [Same cut, a thousand names: renaming, relabelling and the shrinking gene pool](https://genetixbay.com/knowledge/genetics-history/same-cut-a-thousand-names.md) - **Myth:** "A strain name tells you what genetics you're getting" **Verdict:** Busted. Genetic studies of retail cannabis show the same name often hides different genotypes. A name is a claim; documented lineage and DNA are the evidence Evidence: [Why strain names are unreliable: what genetic studies show](https://genetixbay.com/knowledge/genetics-history/why-strain-names-are-unreliable.md) ## Hot topics - **The flip isn't day 1 of flower: the 10–14 day transition and how to count it**: Your breeder says 8 weeks, your plant takes 10. Nobody's lying: the clock usually starts at first pistils, not at the flip. The data on the 10–14 day transition, and how to count it. [Read](https://genetixbay.com/knowledge/environment/flip-to-flower-transition.md) - **Irradiated cannabis: gamma, e-beam, X-ray, ozone, RF and what they do to your weed**: A lot of legal flower gets zapped before it reaches the shelf. Most buyers are never told. Here's what gamma, e-beam, X-ray, ozone and RF actually do to terpenes, which places make anyone disclose it, and why growing your own skips the whole question. [Read](https://genetixbay.com/knowledge/harvest-cure/irradiated-cannabis.md) - **Breeders vs pollen chuckers: what real cannabis breeding looks like**: Crossing two hype cuts and selling the seed untested isn't breeding. What a breeder actually does, with the arithmetic, and why it's the reason your 'feminised' pack hermed. [Read](https://genetixbay.com/knowledge/breeding/breeders-vs-pollen-chuckers.md) - **Elite clone-only gatekeeping: why the classics live in a few hands**: Some of the most important cuts in cannabis history survive in a handful of private gardens, swapped cut-for-cut or sold for thousands. Here is what the public record shows, and why GenetixBay exists to open it up. [Read](https://genetixbay.com/knowledge/breeding/elite-clone-gatekeeping.md) - **Craft vs industrial cannabis: did legalisation's commercial model hurt quality?**: The founder thinks the commercial legal model was the worst thing that happened to cannabis quality. Here is the case (recalls, irradiation, price collapse, small farms priced out) and what the data don't show. [Read](https://genetixbay.com/knowledge/genetics-history/craft-vs-industrial-cannabis.md) - **Landrace hunting or biopiracy? Benefit-sharing, consent and cannabis**: Nearly every modern line is built on farmers' selections, and almost none of them were ever asked, credited or paid. What the Nagoya Protocol requires, why cannabis falls through the cracks, and what fair landrace work looks like. [Read](https://genetixbay.com/knowledge/genetics-history/landrace-hunting-and-biopiracy.md) - **Patents and the gene pool: who can own a cannabis plant?**: Cannabis plants, traits and methods can be patented, and some are. Here are the public records, the one notable court case, the legal debate about the commons, and why open documentation is the answer. [Read](https://genetixbay.com/knowledge/genetics-history/patents-and-the-gene-pool.md) - **Same cut, a thousand names: renaming, relabelling and the shrinking gene pool**: One state's medical lab records carried 637 strain names that boiled down to three chemical profiles. Genetic tests keep finding one plant under several names and several plants under one. Here's how renaming hides a shrinking gene pool. [Read](https://genetixbay.com/knowledge/genetics-history/same-cut-a-thousand-names.md) - **Why everything tastes the same: the evidence that commercial cannabis is converging**: Thousands of strain names, but most commercial flower falls into a handful of terpene groups, landraces are being hybridised away, and the market pays for THC. The data, and what we do about it. [Read](https://genetixbay.com/knowledge/genetics-history/why-everything-tastes-the-same.md) ## Open trials Controlled side-by-side trials GenetixBay members will run: pre-registered, matched clones or split tents, dry weight and lab results. Null results are published too. - **Tuck vs strip defoliation** (Recruiting at launch) Hypothesis: Tucking fan leaves gives equal or higher dry yield than stripping them, and stripping doesn't raise cannabinoid content. Protocol: Matched clones, split tent: one side tucked only, one side defoliated at flip and day 21; same feed, light and dry. - **13/11 vs 12/12, per cultivar** (Recruiting at launch) Hypothesis: Many cultivars flower fully on 13 h of light (with ramps), giving more total light and equal or higher yield than 12/12. Protocol: Clones of one cultivar in two tents at the same PPFD; 13/11 vs 12/12 from flip to harvest; log days to finish. - **Nitrogen taper vs full feed vs flush** (Recruiting at launch) Hypothesis: Tapering only nitrogen in late flower matches or beats a full feed, and both beat a pre-harvest water flush on yield and resin. Protocol: Three matched-clone groups for the last 3 weeks: N taper (P, K, Ca, Mg, S and micros kept), full feed, plain-water flush. - **Humidity pack vs fresh bud vs nothing** (Recruiting at launch) Hypothesis: Two-way humidity packs don't preserve terpenes better than a well-cured jar with no pack, or one rescued with a fresh bud. Protocol: One batch split into matched jars after the dry: pack, fresh-bud top-up, nothing; same storage, opened on the same schedule. - **Wet vs dry trim** (Recruiting at launch) Hypothesis: Wet and dry trim end with similar terpene content; dry trim loses slightly more trichome heads to handling. Protocol: Branches from the same plants split at the chop: half trimmed wet then hung, half hung whole then trimmed dry. - **Supercropping vs control** (Recruiting at launch) Hypothesis: Supercropping main branches in early stretch gives equal or better dry yield and bud quality than untrained branches. Protocol: Matched clones; supercrop the top branches of half in week 1–2 of flower, leave the rest; same canopy height. - **Mild late drought vs control** (Recruiting at launch) Hypothesis: A mild, controlled dry-back in the last week raises cannabinoid concentration in some cultivars without hurting yield. Protocol: Matched clones; the treatment side is allowed to reach mild wilting before watering in the final 7–10 days; the control is watered normally. - **Topping vs LST in autoflowers** (Recruiting at launch) Hypothesis: LST alone gives higher dry yield in autoflowers than topping, because any setback costs an auto time. Protocol: Seeds from one auto line sown direct in final pots; topped once at node 4–5 vs LST only vs untrained. - **Blind re-test: label vs independent lab** (Recruiting at launch) Hypothesis: Most retail flower labelled in the high 20s and 30s tests in the mid-teens to low 20s at an independent lab. Protocol: Members buy flower legally, record the label, and send a coded sample to an independent lab; only aggregate statistics are published, never named businesses. - **LED vs HPS: terpenes, cannabinoids, blind taste** (Recruiting at launch) Hypothesis: At matched PPFD, DLI and canopy temperature, LED and HPS give equal cannabinoid content; any terpene or taste difference is small and comes from leaf and bud temperature, not the lamp type itself. Protocol: Matched clones of one cultivar in two identical tents, one LED and one HPS, set to the same PPFD map and DLI; leaf-surface temperature and VPD matched with logged sensors; same feed, dry and cure. Swap the lamps between tents on the repeat run. - **Hydro vs living soil: the blind taste panel** (Recruiting at launch) Hypothesis: A well-grown hydro run matches a well-grown living-soil run on taste in a blind panel; any difference in terpene profile is small. The soil-symbiosis question stays open until the data say otherwise. Protocol: Matched clones split between a recirculating hydro system and a living-soil bed in the same room, same light and climate; each side run by a grower experienced in that method; identical dry and cure; samples coded by a third member. - **Auto vs photo sisters: grams per m² per year** (Recruiting at launch) Hypothesis: Per square metre per year, an autoflower line out-yields its photoperiod sister unless the photoperiod side runs a dialled-in SOG or SCROG with a dedicated nursery; the photoperiod sister tests slightly higher in cannabinoids. Protocol: An auto line and its photoperiod sister line from the same breeding project, in equal canopy areas for 12 months: autos sown direct in final pots back to back, photos run with a separate veg area counted in the footprint.