Putting photoperiod CBD seedlings outside in early spring while the days are still short can trigger premature flowering, after which the plant revegetates awkwardly once the days lengthen and loses weeks of growth. Waiting until daylight passes about 14 hours avoids the problem. The sowing calendar on https://calmcbdseeds.com is organised by latitude and shows the safe outdoor date for photoperiod lines alongside the earlier window that autos can use. Starting indoors under long light and moving out in late May works for most of Europe.