winter greenhouse light deprivation march april may ino needed

hello ive veged plants in my greenhouse for feburary and i turned out the lights on the first of march(last week). Even though the hours of sunlight should* be in flowering hours for the next two months, it could be weird for the plants to see days are getting longer. should i pull a blackout tarp over them march and april and possibly(if they go that long) may or should it be fine without. Also when should i pull the tarp over eveing/ morning) and for 12 hours right? thanks

You need a tarp. They need 12 hours of darkness. As dark as possible. Light leaks and 13 to 15 hours of light in flower aren't good. Also, you might want to consider adding supplemental lighting for cloudy days.

Mine are flowering fine with no supplemental in my 4 season