When Should You Flip Cannabis to Flower?

Why

Flip means changing a photoperiod plant’s light schedule. That is a plant that flowers when the nights get long. Indoors, that usually means going from about 18 hours of light to 12 hours of light and 12 hours of dark.

Autoflowers are the exception. They flower by age, not by day length, so there is no flip to wait for.

After the flip, a photoperiod plant often doubles in height, and sometimes a little more, before the tops settle into flower. That is the stretch. You plan the flip so that extra height still finishes under the lights.

So do not flip by the calendar. Plan around your maximum finished plant height.

Here’s my setup.

My tent is 80 inches tall. The buckets are 15 inches. With the light raised as high as it will go, the bottom of the fixture sits 6 inches below the roof.

Measure from the bucket lid to the bottom of the light. In my setup, that is 59 inches.

Then subtract the space you want between the finished tops and the light. I allow 18 inches. That leaves a maximum finished plant height of about 41 inches above the lid.

Grow all the way to the fixture and you can burn the plants late in flower. A lot of growers measure to the ceiling, then watch the canopy walk into the light.

Half of that maximum finished height is the usual starting point. In my setup, that is about 20 inches of plant above the lid.

I flip earlier than that. Mine generally more than double, and some triple, so I flip at about 14 inches above the lid.