If you're planting strickly OD May 1 thru 11. You can start earlier but lights are needed. I have 3 OD germination dates for southern Missouri.  March 1, April 1, and May1 . Daylight isn't quite long enough for veg in March and April, so lights are needed to extend the photoperiod to (15/9) for veg, if planting in May . If you wait till May to germ, you don't need additional lights, and you can do it all directly OD.