The Stretch: What Happens When Cannabis Starts Flowering
Short answer: the stretch is the fast vertical growth in the first two to three weeks after you flip to 12/12 — driven by gibberellins — when a plant can roughly double in height (some sativa-leaning ones triple) while it builds the branches and bud sites your flowers form on.
It’s not trouble, it’s the point, so don’t panic and don’t top or defoliate now — your training window was veg; tuck and gently bend only. Plan for the height before you flip and ease the feed from veg toward bloom rather than yanking nitrogen to zero overnight. Meet the Butcher. Flipped to 12/12, watched all that new growth come pouring out, fan leaves spreading, branches reaching — and thought, right, I’ll tidy that up. Get some light to the lower bits. So in week one of flower the Butcher started stripping leaves and snipping branches off a plant that was already busy transitioning. The plant, instead of building flowers, spent the next fortnight regrowing the solar panels it just lost. Smaller buds, slower finish, and a stressed plant at the exact moment it needed to be left in peace.
The stretch panics people because the plant looks like it’s running away from them. It isn’t. It’s doing precisely what it’s meant to.
The short version:
- When you flip to 12/12, the plant stretches — sometimes an inch or more a day for two to three weeks
- That vertical burst builds the branches and bud sites your flowers will form on. It’s not optional, it’s the point
- Don’t prune, don’t defoliate, don’t restructure during the stretch. Your training window was veg
- Plan for the height before you flip — a plant can double, sometimes more
- Ease the feed from veg toward bloom gradually. Don’t yank the nitrogen to zero overnight
Want the full breakdown? Keep scrolling.
Why does cannabis stretch when it starts flowering?
When the plant gets the 12/12 signal, its hormones shift and it produces gibberellins — stretch hormones — that drive fast vertical growth. At the same time it begins the internal switch from growing leaves to making flowers. It’s not flowering yet in any visible way. It’s preparing the structure. In nature, a taller plant catches more light and more pollen, so it reaches. Your plant doesn’t know it’s in a box in Ireland — it’s running the same programme its ancestors ran on a mountainside in Central Asia. You’ll see internodes lengthen and the whole plant reach. That’s health, not trouble.
How much will my plant stretch in flower?
Plan for it to roughly double. Some indica-leaning plants add 50% and settle; some sativa-leaning ones can triple and keep going. The honest answer is you won’t know your strain’s exact behaviour until you’ve run it once, which is why the safe move is to flip earlier than feels comfortable and leave headroom. A plant that’s a metre at flip can crowd a tent’s light by the time the stretch finishes, and a bud pressed against an LED is a bleached, wasted bud.
This is also where a bit of gentle management earns its keep. Plant yo-yos or a layer of trellis netting let you spread the canopy sideways and guide tall branches back under the light without snapping anything. DIG stock both, and they’re a couple of euro well spent. The key word is guide — bend and tuck, don’t cut.
Should I defoliate or train during the stretch?
No. Leave her alone. If you did your training in veg — topping, LST, whatever your method — the work is done. The stretch is the plant executing the plan you set up. You can tuck a fan leaf that’s shading a major bud site, and you can gently bend a branch that’s heading into the light. But don’t prune, don’t strip leaves, don’t restructure. Every leaf you remove now is energy the plant has to spend regrowing it instead of building flowers. The Butcher learned that the slow way. You don’t have to.
How should I feed during the stretch?
This is the one thing you should be adjusting. The plant still needs nitrogen for all that vertical growth, but the balance is shifting toward potassium and, soon, phosphorus. Most growers move to a bloom nutrient now, which is grand — just don’t drop nitrogen to zero the day you flip. Lean the feed gently toward bloom for the first week or two: enough nitrogen to fuel the stretch, not so much you’re still feeding her like she’s in veg. Think of it as a bridge. The full bloom feed comes when the stretch slows and the first pistils appear.
Then the hard part, which isn’t hard at all: patience. Once the stretch finishes and the pistils show, the plant settles and the buds start to form. The growing’s mostly done. The waiting begins.
Common questions
How long does the cannabis stretch last?
Usually the first two to three weeks after you flip to 12/12. After that the vertical growth slows right down and the plant puts its energy into forming and fattening flowers.
Should I top or prune during the stretch?
No. Topping and heavy pruning belong in veg. Doing it in early flower stresses the plant when it can least afford it and costs you yield. Tuck and gently bend only.
My plant doubled in height — is that normal?
Completely. Doubling is typical, and some sativa-leaning plants do more. It's why you plan for height before flipping and leave headroom under the light.
When do I switch to bloom nutrients?
Ease into it. Lean toward bloom over the first week or two of the stretch, then go to a full bloom feed once the stretch slows and pistils appear. Don't cut nitrogen to zero overnight.
How do I control height in a small tent?
Flip earlier, then manage the canopy with LST, plant yo-yos or trellis netting to spread growth sideways. Keep buds off the light — anything touching the LED bleaches.
