When should I flip to flower?

GROWER ANSWER

When she's ready, not when the calendar says. Before you touch the timer, check that she's healthy and growing, recovered from her last topping or transplant, showing grown up signs at the nodes, and built out enough to fill your space. Then measure, because many plants roughly double in height over the first couple of weeks of flower. A ready plant should sit around half of your usable height.

The flip isn't a date you arrive at. It's a state she reaches.

What "the flip" means

The flip is switching a photoperiod plant's lights to 12 hours on and 12 off, which tells her to start flowering. Autoflowers flower on their own clock, so there's no flip to time.

Why week four isn't a signal

Week four is an average of a thousand other people's grows, and none of them was standing in your tent. Four weeks makes a squat little plant in one room and a monster bush in another.

Here's the part that proves it. A healthy cutting taken from a mature plant can be flipped soon after she roots, and she'll flower. A seedling flipped the same week she cracked barely does a thing. Same light, same tent, same days gone by. One grew up, one's still a kid.

Why flipping on a number backfires

When you switch to 12/12, she doesn't start making buds at the size she is. She keeps growing fast through the stretch, and a lot of plants roughly double in height over the first two to three weeks. Compact plants tend to stretch milder, around 1.5 to 2 times their size at the flip. Stretchy ones can go 2 to 3 times. Flip day isn't final height. It's the launch pad.

The opposite mistake stings too. Vegging forever, waiting for her to look perfect, just runs her past the space you have. A tent is a fixed box. Ready and recovered beats big.

Let the plant veto the flip, then measure

1. Vigor. Is she healthy and actively growing, new tops reaching, drinking on a steady rhythm? Stalled, pale, drooping or fighting pests, she vetoes it. Flower won't fix a sick plant, so fix the problem first.

2. Recovery. Did she bounce back from the last big thing you did, like a topping or a transplant? The stretch is one of the most demanding phases of her life. Give a transplant about five to ten days to settle.

3. Maturity. Look for alternating, staggered nodes up the stem, or preflowers at the nodes. That's her grown up signal.

4. Structure. Is the frame built out enough to fill your space, or close enough that the stretch finishes it? One tall plant in a big empty tent wastes light.

5. Then the space. Only now does the tape come out.

The space math. Tent height, minus the pot, minus the clearance your light needs above the canopy, is your usable height. A 72 inch tent with a 12 inch pot and 18 inches of light clearance leaves 42 usable inches. Flip around half of that, about 20 or 21 inches, a little sooner for a stretchy plant and a little later for a compact one. Unknown genetics? Treat her like a big stretcher.

Already taller than half? Train the stretch down instead of hoping she behaves. You can keep spreading a canopy wider in the first weeks of flower. You can't get vertical space back.

What not to do

Don't flip because a buddy did, or because the nutrient chart has a flower column starting this week. None of that is a readiness signal.

Don't flip a plant that's still recovering. She starts the hardest phase of her life with a limp.

When it's something else

• Deciding whether to top or tie her down first: see Should I top or LST my plant, and when?

• Thinking about a strip before the flip: see Should I cut the fan leaves?

On our shelf in Worcester: Light timers and fixtures are in Grow lights, and tents in Grow tents.

Keep going

Watch the episode: When to Flip to 12/12: Read the Plant, Not the Calendar on MyRemy Live.

Read her first, then fit her to the room. The whole system is written down in the free Stability Playbook. Get the free Stability Playbook