A sunrise/sunset ramp is a controller setting that brings a dimmable fixture (usually LED) up from off to full power over a set time, and back down at the end of the day. Ramps of 15–60 minutes are common. They imitate the gradual dawn and dusk plants evolved with.
In practice
Ramps soften the sudden switch from darkness to full intensity, which gives stomata and leaf temperature time to adjust and avoids a sudden spike in room heat and humidity load. They also reduce inrush on the electrical supply.
They add very little light. A 30-minute linear ramp to 900 µmol/m²/s delivers on average 450 µmol/m²/s for half an hour, about 0.8 mol/m²/day, so two ramps add about 1.6 mol/m²/day. This is why the founder's 13/11 practice amounts to roughly 12 hours of high intensity, with ramps making up the rest.
Count ramp time as light time for flowering purposes: plants sense even dim light as day. If you add 1-hour ramps to a 12/12 schedule, your real night is now 10 hours, which some cultivars will not tolerate.
Don't confuse with
- 13/11: a schedule; ramps are one way to fill its extra hour.
- Light leak: unplanned light during the dark period.
Myth check
Ramps are Grower practice; there is little controlled cannabis evidence of a yield effect either way. Their value is in smoother transitions and control.
