When / if / how to thin native wildflowers? (standing cypress)

I spread some standing cypress seeds for some height in my garden several places. Most places none or only a few are coming up but conditions must be perfect here as it seems they all are coming up here (it's a place that gets no direct sun but if they grow up a foot they will, haven't had luck here before with other wildflowers). Best to thin em out in a couple weeks or something?… Let em be? Thoughts?