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gibberillins explained
Gibberellins in Cannabis: The Long-Form Big Red Deep Dive
(Part 1 — Foundations, Functions, and Hidden Influence)
If you talk to growers long enough you notice nobody ever brings up gibberellins unless they’re either a hardcore plant nerd or they’ve messed around with feminized pollen projects. Auxins yeah everybody knows auxins. Cytokinins sure that’s the growth booster folks like to name drop when they’re feeling scientific. Ethylene gets a little love when herm talk comes up. But gibberellins? These things are like the quiet kid in the back of class who barely speaks yet somehow ends up changing the whole damn school. That’s what GA does in cannabis. Silent but influential. Background but essential. Sleepy but powerful as hell.
You don’t see gibberellins on the bottle of any common nutrient line. You don’t walk into a hydro store and hear someone say yo my GA levels are off the charts right now. But whether you’re paying attention or not your cannabis plants are constantly negotiating with these hormones. Constantly detecting little shifts in the environment. Constantly adjusting growth momentum because of what gibberellins whisper inside the cells.
Gibberellins are growth accelerators. Not sloppy growth, not panicked stretching, but momentum growth. They give the plant permission to expand with confidence. They loosen cell walls, pump up enzymatic activity, and unlock the starch reserves needed for seedlings to wake up and push through soil or rockwool. They’re like the green light at an intersection. They don’t force the car to move but they allow movement. Cannabis watches that light. And if the light stays green long enough you get a plant that tears out of the gate like it’s been waiting its whole life to run.
Gibberellins: The Hidden Engine Behind Cannabis Stretch
Every grower knows the stretch phase. Flip the lights to 12/12 and boom your plants start shooting upward like somebody put rocket fuel in the reservoir. Some strains chill and give you a gentle rise. Some triple in size. Some take off so fast you swear they’re growing while you’re standing there watching. What’s controlling that surge? Sure photoperiod shift plays a role. Auxins redistribute. The plant’s internal circadian rhythm resets. But the main hormone screaming go go go is gibberellin.
As soon as cannabis senses the longer night period it triggers a hormonal relay. Gibberellins spike, especially GA3 and GA4. Those are the heavy hitters. They loosen the fibers that give plant cells their shape and rigidity. Suddenly those rigid cells behave like stretchy balloons. Water moves in. Turgor pressure climbs. The walls expand. And the internodes — those spaces between nodes that growers always complain about when stretch goes too far — begin to lengthen.
Internodal spacing is practically a gauge for gibberellin activity. Tight spacing? Low GA. Long spacing? High GA. Super elongated spacing? Overactive GA or a plant reacting to stress, light intensity imbalance, or genetic predisposition.
Now here’s the wild part. The plant isn’t just stretching for the sake of stretching. Gibberellins are part of a strategy. The plant wants to set the architecture of its flowering structure before it commits big resources to bud development. It wants to create the “frame” first. And GA is the contractor that builds that frame. Auxins mark where the branches go. Cytokinins fuel budsite potential. But gibberellins stretch everything out and create the spacing that determines how much airflow, how much light penetration, and how much total flower mass can exist in the canopy.
Too much GA and you get weak branches that can’t support heavy buds. Too little GA and you get stunted clustered nodes that can restrict bud swelling later. Like almost everything in cannabis it’s about balance. And GA is the one hormone growers rarely think about even though it's silently shaping how your plant will handle the next eight weeks of bloom.
Why Cold Nights Stall Cannabis: The GA Temperature Link
Every time a grower complains that their plants stopped growing during a cold snap the explanation almost always ties back to gibberellins. Low temperatures reduce GA biosynthesis. When your nights drop into the mid 50s or low 60s the enzymes that build GA slow down. The plant shifts into a protective state. Growth halts, cell expansion stops, and instead of elongating the plant begins hugging itself tighter.
You can witness this even in clones. Take two cuts of the same plant. Put one in a warm area of the veg room and the other near the intake where it gets those cold drafts. Same light. Same humidity. Same nutrients. But the warm clone stays vigorous while the cold clone stays squat. That is gibberellins right there. Warm temps keep the green light shining. Cold temps turn it yellow at best or red at worst.
Some growers actually use this on purpose. They run cool nights at the beginning of flower to reduce stretch. This is low GA manipulation using nothing but environment. High GA equals tall plants. Low GA equals compact plants. No additives. No sprays. Just temperature control. And cannabis listens immediately.
Gibberellins and Seed Germination: The Wake-Up Switch
If you’ve ever wondered what makes a dormant seed suddenly decide it’s time to wake up the answer again is gibberellins. Inside every cannabis seed there’s a tiny embryo waiting for a signal. Moisture is one signal. Temperature is another. But the internal hormone that actually tells the seed to start breaking down stored starch is GA.
As soon as the seed hydrates, GA levels rise and activate amylase — that’s the enzyme that breaks down starch molecules so the embryo can use that sugar as fuel. Without that spike the seed stays asleep. Nothing happens. That’s why improper storage conditions can ruin germination rates. If a seed is exposed to small moisture fluctuations over time its GA balance becomes chaotic and you get weak or non-viable germination. When you soak or paper-towel germinate you’re basically triggering a hormonal shift that tells the seed hey it’s time.
And this isn’t just germination speed. GA influences the vigor of the first taproot push. High gibberellin seeds send out long confident radicles. Low gibberellin seeds hesitate or grow slowly. This is part of why old seeds start acting like old people — they still work but everything takes longer and they don’t spring out of bed as fast.
Gibberellins and Sex Expression: The Hormone Behind Male Traits
This is where growers suddenly perk up. If you’ve ever made feminized pollen you already know gibberellins are involved. Spray GA3 on a female cannabis plant and you can force her to develop male flowers. Not full masculine reversal like colloidal silver or STS, but enough to produce pollen. The reason this works is because GA influences floral identity genes.
Cannabis has a hormonal tug-of-war controlling sex:
- Ethylene pushes female traits
- Gibberellins push male traits
Increase ethylene and you get more pistils. Increase gibberellins and you get more stamens. Breeders use this on purpose. They want female genetics but they need pollen. So they spray GA to push the plant toward male expression just long enough to collect pollen sacks.
Here’s what’s even more interesting. Plants under natural stress — like extreme heat, drought, or inconsistent light cycles — sometimes produce small increases in GA. And if a plant is genetically unstable those increases can tilt things toward hermaphroditism. It’s not the only cause but it’s a contributor. That’s why stable genetics matter. A strong plant handles GA fluctuations without responding dramatically.
Gibberellins and Flower Formation: The Transition Architect
During early bloom gibberellins are active. They drive the formation of the floral structure: the branching angles, the spacing between bud sites, the length of the pedicels. But as flower development intensifies GA activity needs to taper down. Too much GA late in bloom leads to:
- airy buds
- foxtailing
- long odd vertical stacks
- reduced density
- sativa-like stretching in strains that shouldn’t stretch that way
This is why you see super tight buds under strong LED lighting with controlled temps. LEDs reduce leaf temperature which reduces GA activity, which in turn keeps internodes tight during bud development.
Meanwhile, in full sun outdoor grows GA is more active because leaf temperatures run hotter. That’s part of why outdoor-grown plants tend to get bigger and wilder. A lot of the outdoor “character” people attribute to genetics is actually gibberellin-driven architecture.
Gibberellins in cannabis are one of those deep plant topics hiding in plain sight that almost nobody talks about even though they practically steer the ship when it comes to growth momentum structure and developmental timing. Most growers live their whole career adjusting nitrogen levels manipulating VPD dialing in lighting and training plants without ever connecting the dots to the quiet hormone system that decides whether those adjustments actually work. Gibberellins are like the internal gas pedal and once you understand how they move how they quiet down and how the environment pushes them around you start seeing the plant completely differently. You stop thinking cannabis is unpredictable. You stop thinking genetics alone decide everything. And you start realizing how much of your grow is governed by these internal chemical rhythms happening twenty four seven whether you notice them or not.
A good place to start is understanding what gibberellins actually do. GA is not a single hormone but a whole family of related molecules that act like permission slips for growth. Auxins tell the plant where to grow. Cytokinins tell it to divide. Ethylene decides a bunch of ripening and stress responses. ABA puts the brakes on things. But gibberellins tell the plant that expansion is allowed. They loosen up the walls of each cell and once those walls loosen the plant can take in water and inflate those cells like microscopic balloons. That is your stretch. That is your leaf expansion. That is your seed bursting open. Everything that looks like growth instead of just formation comes down to gibberellins saying yes you may expand now. Without GA the plant would be alive but barely moving.
When a cannabis seed sits dry and dormant the embryo is trapped inside a tough seed coat waiting for the right moment. Water comes in and activates enzymes that wake the seed. But water alone does not make the seed sprout. What actually tells the seed to start breaking down stored starch into usable energy is gibberellin. GA turns on the genes that produce amylase an enzyme that chops starch into sugar so the embryo can start burning fuel. That moment the seed goes from sleepy to active is GA giving it the green light. Old seeds struggle because the hormone system doesn’t fire off the same way. Even if the embryo is alive the GA pathway might be sluggish which is why older seeds benefit from warmth a little extra oxygen and steady moisture. Heat increases GA production so warm germination environments give better success. Cold slows GA which is why seeds in chilly conditions pop slow or don’t pop at all. Already you see this hormone shaping your whole operation before your plant even exists.
Once the seed sprouts GA continues to drive early growth. The first few days of life are almost entirely expansion not division. The seedling is working with the cells it already has and those cells stretch because GA softens their walls. The seedling that bursts up with confidence and reaches toward the light is running an efficient gibberellin system. The seedling that stays small or stuck has a disrupted or suppressed GA system. It could be cold soil waterlogged media old seed stress low oxygen or even excessive light. All those things reduce GA activity. So whenever you see a seedling acting shy think GA. Whenever you see one explode like it wants to touch the sky think GA again. It is the invisible force behind that early enthusiasm.
Move into veg and GA starts interacting with the other hormones that control plant shape. Auxins sit in the growing tips telling them to stay dominant. Cytokinins push branching from below. GA stretches the space between nodes and keeps the internodes flexible. If GA is high you get longer spaces between nodes. If GA is low you get tight compact growth. This is why indica types tend to stay squat. They naturally produce lower levels of active GA. Sativas or tropical cultivars tend to produce more. Even two phenotypes from the same seed pack can have different GA behaviors which is why some stretch harder than others under the same conditions. Light quality matters too. Blue light suppresses GA. Red and far red light increases it. LEDs with heavy blue components keep plants more compact. Old school HPS which is loaded with red made everything stretchier. Growers used to blame “HPS stretch” on genetics or intensity but it was spectrum driven GA activity the whole time.
Temperature adds another layer. Cold inhibits GA production. Warmth increases it. If your veg room has a strong day night temperature drop your plants naturally shrink their GA activity at night which leads to tighter node spacing. If your room stays warm at night GA stays active longer and you get more overall elongation. Some growers actually use a cool night strategy early in flower to reduce stretch. They drop the nighttime temp on purpose to suppress gibberellins. Others do the opposite and warm the room to encourage faster canopy rise. You don’t need exotic plant growth regulators to control structure when environment already manipulates GA for you.
Now the big moment every grower lives for or fears depending on their strain the stretch phase after flip. The minute you tell your plant the days are getting shorter the internal clock shifts and one of the first major hormonal adjustments is a spike in gibberellin activity. That spike is the explosive two to three weeks of vertical lift you get right at the start of bloom. It is not random. It is not chaos. It is the plant reorganizing its architecture for flowering. Gibberellins lengthen cells loosen fibers and create spacing so the plant can set up the framework for buds. This is not wasted energy. It is the plant preparing itself for the heavy lifting of reproduction. Some strains stretch only fifty percent. Others double or triple. But almost all the early stretch behavior is driven by GA.
High nitrogen levels amplify GA responsiveness which is why many nutrient schedules reduce nitrogen at flip. They are not just preventing leafy buds. They are moderating stretch by slowing down the GA pathways. Stress can also affect GA. If the plant is stressed in early flower it sometimes overproduces GA as a response which leads to excessive stretching or uneven branching. Light spectrum also matters. Strong red or far red increases GA and stretch. Blue suppresses it. This is why growers manipulating far red at lights off can tighten internodes if used correctly or blow plants out of proportion if used incorrectly. You are manipulating GA without even realizing it.
Gibberellins also affect sex expression in cannabis. Cannabis is one of those rare dioecious plants where environment plays a strong role in determining sexual expression. Ethylene promotes female traits. Gibberellins encourage male traits. Increase GA and you push the plant toward stamen formation. This is why some breeders use GA3 sprays to coax male flowers out of female plants though most prefer silver thiosulfate because it is more reliable. But GA absolutely influences the balance. A plant under stressful conditions especially heat stress or inconsistent photoperiod may experience hormonal shifts that elevate GA enough to encourage herm tendencies if that plant is genetically unstable. This is why stable genetics truly matter. A stable line has strong hormonal resilience. An unstable line swings wildly. You can see the difference in the way these plants stretch. Stable lines stretch predictably because their GA response is stable. Unstable lines stretch erratically because their GA response is sloppy.
After stretch ends GA needs to quiet down so bud development can tighten and stack. If GA stays too active you get airy buds no matter how perfect the nutrients or lights are. If GA drops too low you sometimes get overly tight clusters that trap moisture and reduce airflow. The sweet spot is a moderate decline. This is why LED bud density is consistently higher. LED lights have lower leaf temperature which reduces GA. They also have more blue spectrum which suppresses GA. High pressure sodium had the opposite effect. It made leaf temperatures high and GA ran hot leading to more internodal spacing. Both situations have pros and cons. Too much suppression and you get a dense canopy that needs extra defoliation. Too much GA and you get loose buds that won’t weigh out. The mastery is in balancing environmental pushes so GA naturally sits in the right zone.
Potassium plays a huge role here. High potassium in early to mid bloom helps modulate GA activity and tighten flower development. Calcium and magnesium also matter because they stabilize cell wall enzymes involved in cell expansion which indirectly affects GA sensitivity. Warm roots increase GA. Cool roots decrease it. High dissolved oxygen in hydro increases GA and explains why aeroponics and DWC plants explode with growth that soil growers sometimes cannot even believe. You are not just feeding the plant. You are feeding the hormone system. When you see roots white thick and breathing they produce and respond to GA with way more efficiency.
Some rhizobacteria boost gibberellin levels naturally. This is why some microbial inoculants cause an unexpected burst of stretch. They are changing the hormone balance not the nutrient balance. Most growers do not realize microbes have hormonal influence but they absolutely do. The rhizosphere is a chemical world full of signals. Bacteria produce gibberellin like compounds or stimulate its production in the plant. Mycorrhizae sometimes influence hormone uptake indirectly by improving nutrient balance. Everything is tied in quietly but powerfully.
Light intensity also interacts with GA. Strong intense light suppresses GA to a point. Dim light increases GA as the plant tries to stretch toward brightness. This is why clones stretched under weak T5 lighting then stopped stretching once moved under strong LED. The plant recalibrates GA based on expectation. Many stretch problems come from low early veg light then sudden strong flower light which confuses the GA rhythm. You want consistent light intensity transitions because GA wants predictability.
As buds form the plant shifts energy to secondary metabolites like cannabinoids and terpenes. GA activity needs to be low here. The plant is not trying to elongate anymore. It is trying to ripen. Late bloom foxtailing happens when GA spikes again from heat light stress or inconsistent environment. Those new flowers are not genetics alone. They are hormonal responses. High GA late in bloom equals messy buds. Low GA equals dense flowers. Simple as that.
The flush stage sees GA drop even further because nitrogen reduces and the plant naturally shifts into a finishing state. ABA the stress brake hormone rises. Ethylene rises. Gibberellin falls. The plant enters the slowdown period where ripening overtakes expansion. You see it in the way calyxes swell while pistils recede. You see it in the resin heavy stickiness of the final weeks. The plant is investing energy in chemical development not architectural expansion.
By harvest gibberellins are practically whisper quiet. The plant is no longer in expansion mode. It is in survival and reproduction mode. The entire journey from seed to senescence has been guided by GA pushing and pulling at the right moments like an invisible hand shaping every stage.
Understanding gibberellins gives you power as a grower. Not chemical power. Observational power. Environmental power. The ability to read why your plant is moving so fast or so slow. The ability to predict stretch before it happens. The ability to reduce herm risk by stabilizing hormonal conditions. The ability to maximize density by honoring the point in time where GA must quiet down. The ability to diagnose stalling early veg growth not by blaming nutrients but by noticing temperature or root zone issues.
You also realize how strain differences come from hormone patterns. Indicas have low baseline GA. Sativas have high baseline GA. Hybrids fall somewhere in between. Some phenotypes have insensitive GA receptors so they don’t stretch even with high GA. Others have hyper responsive receptors and stretch explosively. When you observe your plants through the lens of gibberellins you start understanding their personality. You start adjusting environment based on their hormonal tendencies. You stop fighting their nature and start partnering with it.
Everything you do in the grow room touches GA one way or another. Temperature. Spectrum. Intensity. Watering. Oxygen levels. Nutrient ratios. Microbes. VPD. Photoperiod. Stress. Plant training. Even genetics. Gibberellins react to all of it. And they shape the results of all of it.
Once you get that clarity you reach a whole new tier of growing. You stop reacting to stretch. You anticipate it. You stop fearing herms. You know how to avoid the hormonal conditions that invite them. You stop wondering why buds are loose. You know the GA system stayed hot too long. You stop guessing why seedlings stall. You know GA was suppressed by some environmental hiccup.
Gibberellins are the quiet boss of cannabis growth. When you learn to see them you learn to see everything.
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